F1 EVO Electrical & Wiring      (**some of this information is also on the Instrument Panel page)       Last Modified:             Thursday, 11-Oct-2007 09:06:42 EDT

Circuit Protection

I'll start here by commenting on what others have said time and again. You should primarily protect your aircraft and it's components by protecting the wires with some sort of circuit breaker. IOW, you fuse for the wires, not for the component. The idea is to keep the smoke and sparks inside the wires, and cut off the likelihood for trouble before there's a chance to fry a component or the pilot.  Electrical components are rated for a certain amperage load, and usually have a lower operating amperage range . Once you know those numbers, you can choose the proper wire gauge (although most manufacturers tell you what to do) and then determine what sized circuit protector to use to keep the smoke in the wires and the electrons flowing to your widgets.

Wire AN  Gauge Copper	Circuit Breaker  amps	Fuse  amps
22	5	5
20	7.5	5
18	10	10
16	15	10
14	20	15
12	25/30	20
10	35/40	30
8	50	50

The above table was copied from a Ron Alexander article  in SportAir, 1998, but looks to be directly out of AC 43.13-1b, chapter 11.



Wire Sizing Chart

I was reading through AC 43.13-1b chapter 11 about aircraft electrical techniques and came across a chart that helps you choose the appropriate gauge of wire for a particular project. I thought it was pretty interesting. I was set on using #2 welding cable from the battery to the starter and alternator, but according to the chart all I need is #10 !!!



To use the chart, choose your charging/battery system (mine is 14 vdc) and then go down the column to the number of feet of your wire run, then go horizontally across until you come to the  diagonal equivalent of your needed continuous amperage, then drop straight down from there and read the gauge wire you need. You should go to the next larger wire, i.e. read to the right.  My starter wire run is 14 vdc, goes 12 feet, needs 55 amps. That begets a wire size just shy of ten gauge!!!  So I could use relatively light wire up front. Nice that my EVO has the battery up front.

Having had this discussion, perhaps to maximize the cranking ability, it's probably still a good idea to use at least a 4 gauge wire from the battery solenoid to the starter and back. That thing will need some serious cranking amps! So I think there's a bit more to the wire size determination process than just what the chart tells you, but it sure is a good place to start.

Avionics Circuit Protection Requirements  (*amperage confirmed from manufacturer)


Essential (Avionics/Aux - St Fuse Block) Bus Components:

	Component	Max Draw	Recommended	Switch	Circuit Protection	Notes
1	Horizon 1 EFIS	4 amp*	1.5 amp*	unit	ST Fuse Block	.5 amp for AHRS and 1.5 amp per screen, 5 amp max.  These units are internally fused.
2	GRT EIS ?	1 amp*	1 amp*	none	ST Fuse Block ?
3	GMA-340	2.2 amp*	5 amp*	unit	ST Fuse Block
4	GNS-480 Main	3.2 amp*	5 amp*	unit	ST Fuse Block
5	GNS-480 Comm	5.0 amp*	10 amp *	unit	ST Fuse Block
6	SL-40***	5.2	5 amp*	unit	ST Fuse Block	.27 + 2.1 typical receive and tx, 2 + 3.2  amp max
7	GTX-327	1.8 amp	3 amp*	unit	ST Fuse Block
8	alt field	5	5 amp	none	ST Fuse Block
9	ACS ignition	5	5	key	ST Fuse Block
10	Flap Motor	7 amps	7.5 - 10 amp	grip	ST Fuse Block
11
12

*** for an SL-30, the nav side uses .325 typical, .5 amp max,  2 amp breaker recommended
Total Max Amps Consumed at E-bus: 35.4

W51 Rocker Breaker Components:

	Component	Max Draw	Requirement	Switch	Circuit Protection	Wire Size	Notes
1	Airflow Performance Boost Pump	5*	10 amp*	W51 Rocker Breaker	W51 Rocker Breaker	18
2	Pitot Heat	7.5 - 15  amp*	10 - 15  amp*	W51 Rocker Breaker	W51 Rocker Breaker	14
3	Auto Pilot	2.5 amp*	5 amp*	W51 Rocker Breaker	W51 Rocker Breaker	20	Autopilot .5 amp draw  Ea. servo 1 amp draw
4	Nav Lights	1.2	5 amp*   (1 amp)	W51 Rocker Breaker	W51 Rocker Breaker	18
5	Strobes	5	5 amp*   (7-10 amp)	W51 Rocker Breaker	W51 Rocker Breaker	18
6	Landing Light	9.2	15 amp	W51 Rocker Breaker	W51 Rocker Breaker	14 - 18
7
8
9

Total Max Main Bus Amperage Load: 31.2 amps


Other Electrical Components requiring individual circuit protection:

Component	Max Draw	Requirement	Switch	Circuit Protection	Wire Size	Notes
Elev. Trim Servo	.6 amp	1 amp*	Stick Grip momentary	pop up breaker	22
Dual Plasma III  Elect Ign	2.3  amp	5 amp	none	fusible link?	shielded 18 - 22
Alternator Main Field	55 amp output	30?	Split master	fusible link?	4 - 12
GRT EIS?	1	1	none	pop up breaker?	22

Some of the above details are pending. Some of these items may be powered through a stand alone battery bus. 

Also not that I haven't specified any wire sizes for the avionics. That's because I am getting the avionics pre-wired, either on the bench by my avionics shop and/or by use of the Approach System Fast Stack Pro-G hub and cable system. More on that later.


Grounding:

I plan on using terminal strips to ground avionics and most other electrical components to the battery (or batteries as it may be). I think that way I will have less chance for trouble with noise and corrosion down the road if I use as many return lines as possible instead of grounding to the airframe. Mark at Team Rocket recommends that the engine be grounded to the engine mount, then ground the engine mount to the battery, and also ground the battery to the wing spar splice plates. I will probably set up this way, but I will most likely still run ground wires to a ground terminal strip whenever possible.

The first ground wire I established was a 12 AWG wire from the battery to the ST Fuse Block negative bus. There are 12 gangs on the negative side of the block, plus a main anchor terminal for the master ground. That terminal is hard to get a wire on because of  where I positioned the block, so I connected the main ground wire to the #1 negative ground position on the block. That aux/avionics ground wire is crimped AND soldered to a ring terminal, and is paired with an 8 AWG wire that goes to the right upper corner of the firewall.  For a ground feed through the firewall, I removed one of the AN3 bolts from the angle steel in the corner and replaced it with a drilled AN3-7 and a castle nut. This longer bolt has enough length to accommodate the ring terminal on the 8 wire as well as a ring terminal from the massive braided ground strap that will go to the battery. The firewall corner angle steel is primed with a pretty tough coating and it took quite a bit of sanding to get down to the bare metal. If that steel is like any of the other crap that came from the Czech Republic, I'll need to liberally apply some dielectric grease to keep it from corroding.



I haven't finalized the firewall ground because I may end up putting another tray over on the right side. If so, the large white ground wire will have to run a different course. Any of the bolts on that corner angle, including the engine mount bolt, would be a good ground. I chose not to use the engine mount bolt because I would run out of threads if I put a ring terminal on either end of the bolt. I don't want to have to buy a big assed hardened bolt just for that, with so many other choices available already.

For the main DualBus on the left side of the ship, I ran a separate 8 AWG wire from the primary battery on the right side of the ship to the negative terminal on the left side backup battery. From there, I ran a 10 AWG wire up to the DualBus Main Ground Terminal.. Perhaps an 8 gauge wire between the batteries and 10 AWG to the Main Ground Terminal is overkill, but when I hit that starter key, having a good ground connection should NEVER be a problem.

After establishing this ground/return line network, I went around with a multimeter checking many locations to compare the resistance. I think I've created a very nice ground system. Hopefully that will pay off with less intermittent weird problems down the road.

All that is left now is to add another ground from the battery to the wing spar splice plates. I'll probably use a 12 AWG from the battery to the spar plates. It's only about 12 inches, so a massive wire shouldn't be necessary. Actually, I don't think the wing spar splice plate ground is all that necessary, but I'll put it in just for good measure. Perhaps it will make those big gas cans in the wings less likely to go boom.

On the engine side of the firewall, I used about 1.5 feet of braided grounding cable. I bought the raw cable from ACS, and soldered on ring connectors. One end goes on the other side of the 12 AWG wire at the firewall. I cleaned off some paint and put the other end at the closest corner sump bolt on the lower right side of the engine. I think I would have preferred to just use a 12 or 10 AWG wire, but I had the braid already... so I used it.



Main Power Bus - Blue Sea DualBus

For my main power bus,  I bought a Blue Sea DualBus terminal strip to power and ground the main aircraft electrical equipment, particularly those things that require a panel switch, and are not "essential" to flight. The DualBus is a simple unit with two rows of 10 each  #8 screw terminals, one row for ground and the other for power. The strip handles 100 amps continuous, which is nearly double the output of my alternator.



The pic gives you an idea of what I had in mind for wiring from the DualBus.

A power wire goes from the DualBus to the #1 quick connect .250 tab on the W51 rockers. The #2 tab hooks up to the load (feeds power to the widgets). The #3 tab is not used because these switches will not internally light.  The ground return wires will be brought up from the widgets in pair, and grounded to the DualBus. There is one screw at the aft end (top end in the pic) on each side the DualBus terminal strip for a pos and neg wire from the battery (solenoid via breaker and master switch) or ground terminal down  low.  I will move the power wires shown on the DualBus to the other side and run the ground return wires outboard.

There are two different types of grommets shown near the instrument panel in the picture. One is a plain old rubber grommet from the electrical department at Lowes. The other is a SB 1000-12 Heyco snap bushing  that I bought with some other electrical parts from Mouser. It is a .750 ID nylon bushing similar to the rudder cable SB 625-8 Heyco snap bushings provided with the F1 kit. I have several different sizes of rubber grommet, but only the two sizes of snap bushings. The final grommet decision may depend on how big the wire bundles are, and whether or not there are  obstacles or  a need for a tight turn in the wire.



I ended up not using the green shelf.  I found it to be too wide, and it gets in the way reaching into the boot cowl. I moved the Dual Bus to the longeron at the boot cowl panel. The bus sits just inside the lip of the boot cowl for easy access. The ground side was moved to the top. I figured I'd be a lot less likely to shock myself that way.  I fashioned a mounting bracket out of .032. I removed 3 rivets from the longeron and riveted the bracket directly to the ship's frame. At the bottom of the bracket,  I just glued it using some GOOP. Simple, and no extra holes in the skin.




  Essential Bus - Blue Sea ST Fuse Block

The Essential (avionics, or aux) Bus, or "E-bus", powers all the "essentials" of flight. This bus should power the items that work to ensure safety of flight. This bus is primary powered by a line from the Main Bus (in my case more directly from the output side of the battery solenoid. The E-bus is mostly an avionics bus, but it should also power the fuel boost pump. The E-bus will have two ways to get juice, normally through the alternator and the primary battery, but in case of alternator shut down or primary battery failure, the E-bus will have an alternate path that can be switched on to receive power from the secondary backup battery.

The ST* Blade Fuse Block (PN: 5026) is a 12 Circuit power center  with a built in negative bus is going to be my power AND ground block for the avionics stack and a few essential items. The ST block takes ATO or ATC type blade fuses. The ST block handles 100 amps continuous total, with a maximum of 30 amps at any single fuse.

I bought Smart Glow blade fuses for my fuse block. "When they blow, they glow!" is the slogan. Each fuse has an LED light that illuminates after the fuse burns through. Makes it easy to find the offending culprit to change it out. The only problem is that the Smart Glow fuses don't fit under the clear Lexan cover of the ST Fuse Block, unless you file down the plastic cylinder on top of the fuse that houses the LED and shows the amperage. The fuse bodies are color coded, so knowing the number isn't all that important, once the system is set up. I took a hand file and ground down a sample fuse and did a little test. With just enough clearance under the block cover, the fuse still worked. I blew out a 25 amp fuse on purpose and I can say that the LED's are VERY bright. Only problem with these fuses so far is that they don't come in sizes smaller than 5 amps, so any 3 amp fuses will not glow when they blow.

I mounted the ST block on the right side of the ship in the side wall bay just aft of the instrument panel. The plan is to cover the block with upholstery, but have the block accessible in flight behind a panel. I slightly canted the block so that I can see it better and get fingers on it more easily to change the fuses.  The polycarbonate cover does not fit over the Smart Glow fuses, and adds too much thickness, so if I use the glow fuses, I will have to modify them.

I took some scrap .032 and made a mounting bracket for the ST Fuse Block.  I used four nut plates and 4 #8 screws to mount it up. The bracket has an offset face in that it turns the face of the ST Block toward the pilot about 50 degrees or so.  It's turned just enough that it should make it easier to grab and remove the fuses.



I located a key switch and an eyeball vent in the instrument panel sub frame just forward of the E-bus. I think I'm going to cover this side bay and put an "arm rest" on it. On the front, I think I will make a simple hinged door that swings up to give me access to this entire fuse panel bay.




Depending on how many wires end up clogging the hole through the #2 bulkhead, I may have to make a larger or second hole.  Note that the main ground wire to the fuse block does not go to the empty terminal on the right end of the unit yet. I've since installed an 8 AWG to the ground stud.  Still need to dimple the side skin and rivet the bracket to position, too. If I can get a buddy to help, I'll buck solid rivets. Otherwise cs pop rivets should work just fine.

The main power feed to the E-bus is from the primary battery solenoid on the left of the forward stick bay through an 8 AWG wire. The alternate/secondary power feed to the E-bus is from the secondary backup PC680 battery through a second battery solenoid on the right side of the ship. The alternate battery source comes to the supply side terminal on the primary battery solenoid through a short independent 8 AWG wire from the supply line side of a secondary battery solenoid.   In the event of primary battery failure (extremely unlikely) or alternator failure, I've installed a separate ON ON toggle switch to ground out either battery solenoid. When one battery solenoid is grounded on, the other is always ungrounded, which means turned off. The master which operates the primary side of the electrical system, including the Main bus gets it's ground from the alternate battery toggle.



Battery Bus?

I don't have plans to install a battery bus per se, but I thought I would discuss it. Instead, I have wires direct from each battery to the dual Electronic Ignitions (EI) and the computer brain of the AHRS, which controls the EFIS and is the primary attitude indicator.

As I have spent a lot of time trying to understand wiring diagrams and the layout of various aircraft electrical systems, I have discovered that perhaps I should add a 3rd bus. If nothing else, since I am having dual electronic ignition, I should at least have a separate battery feed to one side of the ignition direct from the batteries. Also, Grand Rapids Technology recommends that the AHRS guidance module be connected to the battery and never shut down in flight. My primary instruments are being replaced by the Horizon 1 EFIS, so it also will need to have power from the battery bus. I have a dual screen, single AHRS system ordered, with an integrated engine monitor. The engine monitor is planned for continuous viewing on the bottom screen. The second  monitor at the bottom of my panel and those engine instruments MAY not be essential for flight. So perhaps I will wire the AHRS guidance system and the top screen direct to the battery bus.

The Battery bus (B-bus) could be just small  fuse block, located as close as possible to the battery. It would be powered directly from the battery positive terminal (or from the BAT terminal of the battery contactor) and is "hot" all the time, without a switch. This bus is commonly used for interior lights, clocks, and hour meters. In my case, it will also be used to feed one of the two electronic ignitions for my engine. To protect this hot battery line, I will probably use 12AWG wire and a 16 gauge fusible link.

A power feed from the battery bus also can power the essential bus. In case of alternator failure, the battery can then feed to a switch and subsequently the essential bus to power the EFIS, NAVCOM, transponder,  and GPS, as well as the fuel boost pump.  Bob Nuckolls has some great ideas about how to set up an alternate electrical line to the essential bus, which includes an in line diode to prevent "back flow" drainage from a secondary battery toward a corrupted alternator.

The B-bus doesn't really need much more than 4 to 6 fuse slots, if even that. I really don't think I need another ST Fuse block here, just a Plain Jane fuse block without any ground terminals. I wasn't planning on any  courtesy lights, or an hour meter or clock (those are in the EFIS). This bus would just be an intermediate to the E-bus and may only have that one line, and at least a feed to one side of the ignition. I could just make individual lines and an in line fuse with a switch, or dedicate a line (with fusible link) from the rocker breakers on the panel to the E-bus as an alternate battery feed.  I'll have to contemplate that one. A dedicated battery bus is a good idea for future expansion.

I found a couple 4 gang ATC fuse blocks on the web. Two in particular looked workable. I was trying to fit a battery bus in the sidewall bay with the ST fuse block. A 6 gang block was just too large. A 4 gang would be about right. Hella sells some ATC fuse blocks with splash proof lids. One style has the wires coming  out the both sides. One style has the block on pedestals and the wires come from underneath. I think what I want to do is use the pedestal style, but I bought both types just in case I decided to change my mind. In fact I bought two of the side wire styles because they would be handy for adding some farkles to my motorcycle.

The Hella pedestal style splash proof  fuse block looks like this:












The fast on quick connect spade terminals aren't pushed on the male spades of the fuse block all the way. Those left three terminals especially do NOT like to come off if you put them all the way on. They do clear the  mounting face under the pedestal feet when completely connected. I may, however, give my self some more working room for the wires and put 1/4 or 1/8 inch spacers under the feet when I screw the base down. That will make it easier to get the feed wires to the spades underneath. Also, more than likely, if I use this Hella fuse block B-bus, I will make quite a large hole under the base to accommodate bringing wires through the bulkhead to the spades on the block. Hmmmm.... maybe I should use the side terminals after all. They have a larger footprint, but will be easier to service if necessary... hmmmm...

Still not sure I'm even installing a battery bus.



Odyssey PC680 Battery

The Odyssey PC680 battery is a smallish long storage life and high cranking dry cell 12 vdc battery with many features that are optimal for use in aircraft. On the EVO model F1, this battery  easily mounts under the pilot's right knee in a small bay in the floor. The Fuselage3 page shows the mounting tray and location.

I bought M6 bolts for the battery terminals at Auto Zone to replace the little screws that came with the battery.

The marine variations of the Odyssey batteries are identical to the type that I am using.From an great article on marine applications of the Odyssey batteries:

    " The Odyssey Battery is an AGM battery that is very unique and technologically advanced. It was designed to meet the demanding needs of the US Military with respect to heat, cold, shock and vibration, and to last much longer than other batteries. It is currently used in tanks, fighter jets, battle ships, and many other military applications. On top of this it delivers higher cranking power while also being the best deep cycle battery available (two to three times the cranking amperage of other similar sized batteries and the ability to be drawn down to 100% over 400 times). Other attributes include the ability to sit dormant for up to two years and still hold enough charge to start the motor it was intended for. This is very important because we often don’t get to use our (planes) boats as much as we would like during the season. The Odyssey battery actually lasts up to 6-10 years which is attributed to it being manufactured with 99.9% pure virgin lead. The US Coast Guard has 500 batteries in 50 Bollinger 87 foot protector class cutters since 1998 without a single failure to date. On top of all this, it is maintenance free and will not vent during normal operation due to its patented technology to reuse its internal gases. It is also the only battery to claim an explosion proof design.

Charging the Odyssey battery is similar to a flooded battery. It is not sensitive to charging like other AGM’s and the Gel batteries. In fact, the Odyssey battery has no restrictions on the inrush of current and will recharge in one third the time of a conventional battery. This allows the battery to be utilized with traditional flooded chargers and typically does not require replacing your current charger in many applications. Most marine three stage chargers available today work very well for charging the AGM batteries. "

These batteries kick ass. I'm thinking seriously about changing out my old wet auto batteries for Odysseys when the time comes. I've had the first battery in storage for well over a year , and the voltage hasn't seemed to drop at all. If the service life is half as good as the shelf life, these batteries should take over the industry.

Now that we've decided where some big electrical components are going, lets start to run some wire!



Power Supply Wire Run

The primary battery in my F1 EVO is located under the pilot's left knee on the floor. The secondary battery is under the right knee on the floor. The main bus is under the left boot cowl (so far) so it can easily feed the rocker breakers in the panel,  and the starter/solenoid at the firewall. The Essential (avionics, aux) bus is located in the right sidewall bay to the side of the pilot's knee just above the right battery.

For reference, I have been looking at Bob Nuckoll's  AeroElectric Connection pages and Randy Pflanzer's set up and wiring diagrams. My application is a dual battery, single alternator F1 EVO, so most dual alternator, rear battery setups won't work for me. But it's a good start to check out those that have come before. Randy's diagrams and wiring set up is VERY well thought through and quite detailed. Of course AC 43-13-1b is helpful, too.

My EVO battery location, per TR's suggestion, is on the floor just in front of the wing spar on each side of the forward stick bay. Tom Martin has placed his single EVO battery in the center bay, forward of the stick bay. After having installed the fuel pump, filter, selector and lines in the forward center bay, I could still have room for one if not two batteries in that compartment. Had I not already made the trays and drilled the belly skins for rivets, I might have considered moving the batteries farther forward into the center bay.

The first big #4 AWG wires  go left to right over the top of the batteries through grommets or bushings in the walls of the bays. The wire run to the left is going over the top of the battery at the front end of the battery bay, along the aft side of the #2 bulkhead. I extended the battery hold down arm hinge from the lip of the top of the bay so that I could put a pair of Adel clamps (or screwed zip ties) along the bulkhead  to support the wires before going through the wall into the center stick bay. I drilled the location to allow at least a 3/4 opening for big wires to go back and forth. I may need a bigger opening here (and elsewhere), but I started with a 3/4 ID grommet, which requires a 1 inch hole.  The wires to the right are going to exit the battery bay directly in front of the negative battery terminal. 

The main airframe negative ground return 8 AWG wire comes from an AN3 bolt in the firewall's upper right hand corner, down the back of the instrument panel sub frame (#2 bulkhead)  and then through the floor bulkhead direct to the battery negative ground terminal. I also installed an 8 AWG ground wire to the Main Ground Bus (the DualBus terminal strip) from the negative terminal of the primary battery.There is an 8 AWG wire between the negative terminals on the batteries as well, thus creating a rather strong  and large ground circuit.

I will also run an extra ground wire to the wing spar splice plates at the rear floor of the battery bay once the wings are installed. As of yet, I don't have anything electrical grounded to the airframe, and I don't plan too. Everything is directly grounded to the batteries, either directly or indirectly through a bus or feeder wire. So I'm not sure grounding to the splice plates is all that necessary. One would think that the wings should be fairly well grounded to the fuselage given the thousands of bolts that are used to keep the wing spars bolted to the canoe. But TR sez I should ground to the splice plates, so I will.

The primary positive power #4 AWG wires go from the primary battery to the "BAT" side of the primary battery solenoid, then branches out from the supply or "line" stud of the battery solenoid.  An 8 AWG wire makes a short run to the Main bus (which is just a Blue Sea DualBus terminal strip near the rocker breakers behind the left instrument panel). A separate 4 AWG wire goes from the line side of the primary battery solenoid to the BatterLink ACR isolator. Another 4 AWG feeds from the line side of the primary battery solenoid to the BAT side of the starter solenoid, now relocated to the right side of the ship. An 8 AWG wire branches from there to the E-bus. 

The ST Fuse block that is my E-bus actually sits on the side wall just above the rudder cable. So many pos and neg wires have to penetrate the #2 bulkhead to the ST Fuse block to get ground AND power. The large aux power wire as well as a hefty ground wire will go through the 3/4 grommet in the bulkhead to the pos terminal on the fuse block. From there, all the ground and power feeds will traverse back through he bulkhead grommet and then back to the floor, or most likely continue upwards to the avionics. I think I'm going to need a bigger (or additional) hole.

Mark at Team Rocket said that he ran his wires along the forward edge of the #2 bulkhead in a series of 1 inch Adel clamps. I kept all the wires aft of the #2 bulkhead until they reach the instrument panel uprights. This keeps the wires away from fuel lines and my feet.

I reversed the stainless #10 nuts and screws you can see on the #2 bulkhead which hold Adel clamps. You are really supposed to put the screw pan head on the rubber loop side of the clamp. The #10 - #12 Adel clamps are so beefy and the loop is so far from the screw, I don't see any problem with putting the nut (and threaded screw end) on the "working side" of the clamps. Just need to make sure that the threads don't cut into the clamp. Certainly more chance of me hanging my heals up on the nuts compared to a pan head, and I reversed the nuts and screws just to try to keep my heels from getting scuffed by the screw ends.

I did find that the #12 Adel cushion clamps are too small for all the wires that I needed to run. I was running out of room in the clamps before even bringing stick, servo, autopilot, or lighting wires to the front. So I made an order to Spruce and got some #16 and #20 WDG Adel clamps. Good thing I made the battery hold down hinges so far away from the bulkhead!

I used my big step drill to make 7/8 holes from the right knee battery bay, into the center stick bay, and then in roughly the same location into the left knee (aux battery?) bay. On the left side, I will keep the wires as high as possible. I've made another hole from the left knee bay to the forward (pilot) footwell. That hole will feed supply and ground return wires up the left side of the #2 bulkhead. I drilled out a couple existing rivets to allow attachment of #12 Adel clamps. I may not need Adel clamps quite that large, but I'm starting with #12's so I make sure I have more than enough room for the cushion clamps.The existing tooling holes are quite nice for mounting even more Adel clamps for the supply wire runs up the forward (backside) side of the #2 bulkhead.

For the negative ground return wires I used 8 AWG from the negative terminal of the primary battery all the way to the DualBus main ground strip. I also ran a combined ground using 8 AWG to the upper right corner of the firewall, and a short run 10 AWG wire to the ground bus on the ST Fuse Block (aux/avionics supply and grounds).

'Lectric Bob and countless others suggest that you keep the 'fat wires" away from the "skinny" ones. Also, my research suggests that both the starter and alternator wires should run together on one side of the instrument panel and all the other wires, electronic ignition and particularly sensor wires, should go as far away on the firewall as possible. In my case, I relocated the starter to the right side so that the main power 4 AWG feed goes from the alternator to the starter solenoid supply stud, then through an ANL fuse, then to the battery system. All this runs at the very outside corner of the right side of the firewall. The other "skinny" wires run through the middle and slightly left of center through the firewall. The mid wires decrease in size and voltage from right to left. The rightmost wires are the high voltage ignition cables, then the EGT/CHT sensors, then the very low voltage sensors at the left side. Supposedly, this type of arrangement keeps the little gremlins at bay. Hopefully, I have enough separation and good enough grounding and shielding to keep the noise AND the gremlins out.
























Battery Solenoid

I originally purchased a pair of Cole-Hersee model 24115 Continuous Duty 85 amp battery solenoids (relay, contactor, actuator, etc...) from Van's and Wicks. 

These things couldn't be simpler to install and operate. You connect the BATT end of the solenoid to the positive terminal on the battery via a big  wire with a crimped and/or soldered 5/16 terminal. The other "line" (or "supply") stud of the unit is the same size terminal and that one goes to your main bus or whatever else you want to send switched power.

To operate (close) the normally open circuit, and "turn on the battery", it only takes one wire (well, one simple "circuit", I suppose...). All you have to do is run a wire from the smaller middle post on the battery solenoid, which is a 3/16 terminal, to a switch, and then from the switch to a ground negative source (return line, negative bus). Close the BAT switch, the current at the battery solenoid 3/16 stud goes to ground, the solenoid magnetizes and operates, et VOILA!  You got power!  Sweet, huh?!

These little gems are going right into the forward stick bay. In the pic to the left, I located the right (secondary) battery solenoid to two factory located rivet holes. It happened to match perfectly with the factory rivet holes, and was a good high location for the solenoid, with plenty of clearance from the control tube and way up off the floor. I installed TWO battery solenoids and they are located in mirror image locations in the forward stick bay.

I need to power the Main and Essential buses from the supply side of the primary battery solenoid. The positive wire (and of course the grounding wire) that goes to the DualBus terminal strip on the left side of the ship is a 4 gauge. More on the DualBus main bus down this page.

I used 18 gauge wire from the battery solenoid 3/16 post to a split master switch that my friend John Watler gave me.  The ground for the split master battery switch is supplied through an ALTERNATE BATTERY ON ON toggle switch. The ALT swtich gets it's ground from an 18 AWG to a ground terminal on the E-bus (ST Fuse Block).




After an email on the F1 list describing one builder frying his Garmin radio due to a "spike", I started getting nervous about protecting my avionics from the spikes that supposedly come from the starter, and from a runaway alternator. I do not have an avionics master switch. Not so much because it's a single point of failure, but more so because I'm lazy and don't want to install or use an extra switch. My EFIS is going to be always on, and so is the electronic ignition. The Garmin stack can just be shut off at the faceplate, so I'm not so worried about those, particularly at startup.


Dual Battery / Alternate Battery Source

Installing a backup electrical system is a good idea in any airplane. Perhaps it's a must if you have dual electronic ignition, as in my F1. There are many ways to arrange redundant or backup electrical systems. Primarily, they are dual alternators or dual batteries or both. I may install a backup alternator on the engine vacuum pump pad down the road. However, I have more faith in the integrity of batteries (especially the Odyssey) over the reliability of an alternator. I have had a few aircraft alternator problems over the years, and feel much more secure in having a charged pair of batteries getting me through a flight. Of course the chances of two alternators failing is quite remote, too, but not as remote as two Odyssey batteries failing.

I was trying to decide on how to setup my dual battery system. First, what batteries to use. I was considering using two smaller batteries (to save weight) and running them concurrently (get it, conCURRENTly?) so I could be sure and start the plane. However, after thinking it through, I decided to sacrifice the weight and install two full sized PC680's. That's another 14.5 pounds up front, which is significant to gross weight, but probably not to CG since the batteries sit so close to the wing spar . Perhaps I should just lose 20 myself to compensate for the weight. I certainly have adipose tissue to spare.

When I wired in my second PC680, I had to take steps to combine the battery power as well as steps to separate the two batteries within the electrical system. When everything is running hunky dory, which should be 99.9% of the time, both batteries should be working together ("combined") and charging from the single alternator via the BatteryLink ACR.

However, when things go bad, like the primary battery gets weak, or the alternator fails, then it is desirable to have a secondary backup battery system, completely separate from the primary electrical source. The BatteryLink ACR isolator and two battery solenoids accomplish this for me. If the primary battery or alternator goes down and the voltage drops below a preset level, the BatteryLink relay opens automatically and the secondary battery system is cut off from the primary charging system. Usually, the only thing the secondary battery is doing is powering one of the two electronic ignitions and the AHRS of the EFIS. The primary system is still powering it's EI, the AHRS and both buses.

Now, to put the backup battery (and backup electrical system) into service:  Flip the ON-ON toggle switch on the instrument panel marked "Alternate Battery", and power is fed from the secondary system to the supply side of the primary battery solenoid. When you switch from primary to alternate (secondary backup) battery, the roles of the system reverse: the primary battery is then just powering the AHRS and an EI, and the secondary battery powers both buses. The flow from the secondary battery to the primary battery is cut off, the secondary battery now powers both buses and each battery still feeds the electronic ignition.

Side note: Either battery, or the E-bus, can directy power the EFIS. GRT made it so that the EFIS system automatically chooses the strongest power source hooked to it. The EFIS/EIS system has it's own internal protection, and three separate power feeds. Pretty cool.

The dual battery and BatteryLink ACR ("isolator") in the front of the cabin on the floor looks like this (except later on, I turned the BatteryLink upside down):

The backup secondary alternate battery feed is set up to run one electronic ignition and add one feed to the GRT EFIS's AHRS. That's all the backup battery will do the vast majority of the time. However if needed, the alternate battery backup feed can be switched to power the both the Main and E-bus. There is no switch in my system to shut off either bus, you just have to turn off whatever you don't need by the rocker breaker switches in the instrument panel, or directly at the device you want to shut down.

The main/primary/master battery is on the left side of the ship.  The backup/secondary battery is in the mirror image location on the right side of the ship. The plan is to rotate one of these two batteries out of service every other year (with the ELT battery). The fresh battery goes into the right (secondary) side, and the old right side battery goes over to the main battery side on the left, which is the battery used to start the engine. So the best battery is always the backup, and the old battery gets used and abused on the left side of the ship. If the older battery isn't good enough to start the plane, it's not good enough to start a light with, either!  I sure want to have the very best battery in the backup slot so I have the strongest battery to power the ignition and the E-bus when I need it the most.



Both batteries are hooked to the bat sides of the solenoids, with jumpers from each to the BatteryLink ACR. The alternator B-lead comes indirectly to the supply side of the primary solenoid. When the master is on and the primary battery solenoid is energized, the alternator can charge both batteries, but it goes through the solenoids. Both buses are also wired to the supply side of the primary battery solenoid with a jumper to the supply side of the secondary battery solenoid. One switch, and ON-ON toggle operates both battery solenoids. Therefore only one battery system can operate the bus at one time.

The batteries are indirectly linked through the BatteryLink ACR. That unit has diodes in it and regulates the flow between the batteries (and the charging system). When the batteries are "combined", the primary battery charges the secondary battery. When not combined, the secondary battery can be completely isolated from everything. The secondary battery is usually automatically charged or disconnected by the BatteryLink ACR. It can be manually removed by a switch on the panel that will open the circuit at the BatteryLink.

At start up, the split master is turned on. That closes the primary battery solenoid (if the battery switch is set on primary..), but the secondary battery solenoid remains open and the secondary battery is protected/isolated from the system. When you first turn on the electrical system, the BatterLink relay is automatically open for about the first minute of operation. Having the isolator open (off)  protects the secondary battery and the BatteryLink isolator during engine start.

In case of alternator failure, or if one of the batteries discharges for some reason, the isolator senses the discrepancy, and automatically disconnects (opens it's relay) the batteries. That's the purpose of the BatteryLink ACR, it automatically combines both batteries to charge them, or in event of discharge or alternator failure, it disconnects (shuts off) automatically (or you can switch it manually) in order to save whatever energy remains in one battery without transferring the remaining energy to the other battery. More about that below.

My EFIS will flag me that there is a charging problem. At that point I can choose to continue in the normal primary mode, or switch to the secondary alternate battery to power the buses. Only one battery ever feeds the buses. With the isolator open and the main battery switch on normal (or primary.. haven't decided on nomenclature for placards yet) only the primary battery is supplying the buses. If I switch to BACKUP or SECONDARY or ALTERNATE BATTERY, then only the right side secondary battery is feeding the buses. How do I accomplish this? Well, my ALTERNATE BATTERY toggle is a DTDP ON-ON switch.

Normally, the toggle has PRIMARY ON ( or "Normal"). An 18 AWG ground wire from the E-bus ground bus grounds the split master switch, which when switched on, grounds the primary solenoid and closes the primary solenoid relay. If necessary, I can switch the toggle to the other secondary/alternate ON, and that action grounds out the secondary solenoid and UN-grounds the primary solenoid which locks out the primary battery. The ON-ON switch never allows you to have both battery solenoids closed ("turned on") at the same time.

Getting confused? Me too. I'm still working on this system. Hopefully the wiring diagrams below can make some sense out of this thing. I think I'm getting closer to having a single switch alternate electrical source.



After feeling confident that I had the alternate battery source and battery isolator concepts in hand, I went ahead and installed the ON-ON toggle in the instrument panel. I had to remake a couple of the wires because I put a pair of 5 amp breakers in the panel between the toggle and the master switch.



I could have spread the components out a little, but I wanted them in close proximity to the ignition and master switch. Also, you never know what might come along down the road. I still have a little room above the toggle to install a couple more switches, idiot lights or breakers.

Note that I finally riveted in the Radio Rax rails for my avionics. I'm not really even close to being ready to order the avionics, but I was tired of working around the clekos.

There is an alternate toggle switch diagram next to the split master wiring diagram farther down the page. I set the switch up so that when ALTERNATE (or SECONDARY) BATTERY is selected, the toggle switch, which is a DPDT ON-ON 20 amp switch, the BatteryLink ACR isolator is forced to disconnect the batteries by grounding out the isolator's switch.



Battery Isolator

Since I am planning on a dual Plasma III electronic ignition, I am installing backup battery alternate electrical system. Keep in mind, the "fail safe" built in to the Plasma III is that it will run all the way down to 5 volts. At 5 volts, nearly everything else in the ship has probably stopped working. But the engine keeps firing!  And since the electronic ignition works down to such low voltage on such a low power draw, the theory is that you will run out of gas before you run out of electricity to continue to run the engine. Especially with two batteries to work with.

The backup battery might be good for many things, keeping the Plasma III system energized and thereby keeping the engine running in event of an alternator failure is just one. Back up power for the E-bus avionics is another. Also, having extra battery power if you forget and leave the master (with the primary battery) turned on and kill the primary battery is a nice thing if you need to start the engine. Especially if you are at some remote Podunk strip with no open facilities.

Well, I've purchased another Blue Sea item that has just come out for marine use that is used to charge and regulate two battery banks.

The CL-Series BatteryLink™ ACR (Current Limiting)  is a battery isolator device with many features:




Starter Solenoid  and Starter  

The Sky-Tec NL149 inline high torque starter is a bit heavier than the other models of Sky-Tec starters. However, it turns a bit slower (for high compression monster motors... 6.5:1 versus 4.3:1 ratio), perhaps as slow as OEM and maybe even a little slower. But, the starter uses less amps to turn over. The max voltage this baby uses is where their other starters begin to draw... 185 amps!  The NL can use as little as 125 amps to crank an engine. That's a good thing. My electrical system (particularly the BatteryLink ACR isolater) can handle this load for very short durations in a snap without getting fried.

My engine has a slightly higher compression ratio than stock, so a high torque starter is a good thing. Also, then engine has dual electronic ignition, so it should be easier to start the engine, even if it doesn't crank as fast.

The Sky-Tec NL starters come from the factory without a dedicated starter solenoid on board, unlike their other starters. I understand that you can mod the starter to make the solenoid that IS on board the NL starter to function as a starter solenoid. But that change creates limitations on how you set up your start system in that you can't use the ACS key starter. So, I'll opt to take the starter as is from the factory and then go ahead and use the ACS rotary key starter switch and the starter solenoid as planned... the old fashioned way, which I already have installed.

I asked the fine folks at Sky-Tec about using 8 gauge wire for my starter. That's reasonable, considering my batteries are in front of my wing spars, not back in the baggage area. If they WERE back in the back, I'd probably be using 2 gauge Bogart cables. Anyway, Rich Chiappe of Sky-Tec fame was kind enough to put up with my rudimentary questions about the NL starter and wiring, and offered a link to his website and an explanation of wire sizing. It particularly related to starters, but looks familiar and the concepts are generally accepted aircraft practices.  Rich told me that I should use a figure of 200 PEAK amps for the NL starter. All I had to do was keep that 200 figure in mind, then refer to the chart on his page that showed the acceptable size of wire to handle a load and 1/2 voltage drop per given wire length. The article then suggests that there could easily be another 1/2 volt drop induced by the solenoids. Simply stated, once you figure the length of wire needed from your battery to your starter, use the chart to figure out what gauge wire to use. You want to extrapolate to the next larger wire gauge. Then for safety sake, step up one wire size. Then perhaps step up one more wire size due to the extra 1/2 volt induced by the solenoids. Also, the article suggests not to forget that your supply wires are only as good as the ground wires. Don't forget that the starter (and all those other electric widgets) are only in the middle of the loop (circuit), and that the grounds have to be as good as the supply. So make sure your ground wires are as big as the supply wires.

Based on the information I am using, I could extrapolate to a 10 gauge wire, if I only have to go 5 feet. Then step up to an 8 for safety, then perhaps a 6 for additional induced voltage drop in the system.  I already have 4 awg gauge wire to the start solenoid, and was contemplating replacing it with 8. Now I think I'll stick with what I know has worked for others.


The standard aircraft starter solenoid (contactor) is an intermittent duty Cole-Hersee model ES-24021. This unit looks very similar to the battery solenoid except that is has two small terminal 3/16 screws and the body case is Bakelite (or similar insulating material). The starter is normally open and when you switch positive current to the unit, the solenoid activates and current is passed from the battery terminal on one side to the starter terminal on the other. I had a little trouble figuring this unit out. There is a big "S" near one of the 3/16 post for "switch" and an "I" near the other, which stands for "illuminate" or "instrument" or just plain "idiot" light. When the solenoid is operated, current is passed to the "I" terminal so that you can hook up an idiot light. That's just in case your starter gets stuck in the "on" position.

**I could get by without this stand alone starter solenoid, but I installed it anyway. I am purchasing a Mattituck TMX IO540, and they come with a new Sky-Tec NL149 inline compact high torque starter. Some Sky-Tec's starters have an on-board in-line starter solenoid. The NL models have an onboard solenoid, but it is not used for starting. Having said that, a little fairy told me that you CAN modify these NL starters and use the onboard solenoid to use as a starter solenoid. The down side is that you cannot use an ACS rotary key switch with start features to operate the NL starter with the solenoid modified for starting. Bummer. But I understand that if you go by the gospel of Bob Nuckolls and use toggles and a push button, the NL starter will work well using it's own on board modified solenoid as a starter solenoid, and that the company will stand by the modified starter! Sweet!

I had a little problem when I was bench testing this little guy. It wouldn't work. Well, duh, no ground. So I clipped a ground  from the metal housing (one of the "foot brackets") to the neg battery terminal. Then it worked just fine.

Originally, I was going to put the starter solenoid near the left side of the firewall. In the end, I mounted it on an extruded angle bracket on the right side firewall upright. Drilling the holes was a bit of a bitch with my crude tools, but I got it accomplished. The starter solenoid is just below the corner, as high up away from my feet as I could manage, and just below the brake fuid reservoir in the corner.

I used 4 AWG gauge wire for the 5/16 terminals on the starter (from the line side of the battery solenoid), but I'll use shielded 20 gauge wire to power the 3/16 "S" terminal (and ground the housing.. maybe). That wire will goes to the keyed starter switch I bought from Van's. I'm not sure I'll use the idiot light. If the GRT EFIS has a connection for it, I'll use it. I've never had a starter idiot (other than the pilot) on other planes and I don't really find this function all that important, especially with the newer generation of flyweight starters.

When used with my ACS keyed ignition switch, this starter solenoid requires a diode from the switch terminal to a ground at the screw/bolt base of the solenoid unit. The diode was included with the ignition set, and the diode was already assembled with the proper ring terminals and the sheathed wire at the proper length. The diode required for the ACS ignition was installed on the starter solenoid per the ignition switch manufacturer's plans.

The power supply wire for the starter solenoid is 4 AWG and comes from the supply side of the primary battery solenoid, not direct to my battery. The wire to the starter is also 4 AWG and has a simple grommet and stainless shield around it through the firewall.  One note here: I put the shield and grommet on "the big wires" before crimping on the terminals.

The switch wire is a shielded 20 AWG wire from the ACS keyed ignition switch, as required by the ign switch instructions. The ground sheath is crimped with the ACS keyed ignition ground wire and the power supply wire (also shielded 20 AWG) ground sheath, all screwed to the ground terminal on the back of the keyed switch. The ground sheaths may not need to be attached or grounded.




Keyed Ignition Switch


I was having trouble finding a suitable place for my ACS  A-510-2K  keyed ignition switch and locks set. I didn't want it in the panel. I wanted it preferably on the right side. I wanted to be able to work the throttle with my left hand and use the key start with my right. Actually, with a dual LightSpeed Plasma III ignition, I don't think I'll really need to catch the engine with the left hand throttle, so I'll probably end up holding the stick back with my left hand to keep the tail down during engine start.

The key switch was going to go in the panel, but the base of the switch is so bulky, it was going to take up a LOT of space. The F1 panel isn't all that big, and finding an appropriate nook was necessary and troublesome. I was going to put it on the bulkhead at the right just below the instrument panel, but thought that  I would probably try to stick an eyeball air vent there.  

Finally, I was looking at the panel. Wondering what the hell I was going to do with that  single open bolt hole between the other four AN3 bolts I was using. Hmmm... nope, can't fit it in there.  I was looking at the back of the sub frame and  just didn't like ANY location at all. Finally I checked out the area where the special angle shims are used to bolt the bottom of the instrument panel sub frame parts to the bulkhead. That looked like a great place. 

Now comes the problem. I brain farted. The 7/8 inch threaded key barrel of the ignition switch was too short, and the base was too wide. I took the bolts out of the angles and removed the R4 shim. Thankfully, the switch placard covers the bolt holes perfectly. The switch sits in the panel at an angle due to the panel support structures, but I was able to work around that. I used my step drills from each side and went all the way up through the pilot hole to 7/8. Stuck the barrel through the hole. Drat, still not enough to make the knurled nut look right. Also, there was some concern about how much support the instrument panel was going to get.  

I decided to cut the R4 shim into pieces and place it between the panels ABOVE the other thick aluminum part (which the ignition barrel now goes through).  I trimmed two small pieces of the R4 shim, drilled out that tooling hole between the other support bolts, and used two opposing R4 shims there to support the panel. I put an AN3 -7 through there and bolted it up. It pulled the panel right back against the sup frame, worked beautifully. Between the single shimmed AN3 bolt and the steel barrel of the ignition switch, I think the right side of the instrument panel will be supported beautifully.

You can see in the pic that the bolt isn't exactly centered in the angle shim. Well, I can live with that. I actually used the original bolt holes I drilled in the shim, and then trimmed the part to fit.

What you cannot see is that there is a reverse twin sandwiched in between the panels directly behind the R4 shim (as TR planned, just not in the factory location). That squares up the panel, bolt, and nut so that everything fits flush.

Not so, for the ignition switch. It sits at an angle. How to remedy that? Well, you could shim between the panel and the body of the ignition switch. That's not too hard. I thought about gluing up a series of .032 sheet, or just mill down a nice thick piece of  1/8 aluminum.   What I chose to do, was shave off the knurled nut that locks down the barrel to the face of the instrument panel. I had to grind down the nut anyway, because the barrel didn't fit far enough through the panel. I had to trim it back half way through the knurled half of the nut. So I just ground the nut at an angle.

Some things worth noting about this switch...  First off, it requires