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Re-wire for electronic ignition

cdeggz

Well Known Member
Hey Everyone,
My dual magnetos are close to the 500 hour mark so I’m looking at changing my ignition system. My plane already has dual alternator and dual battery, so I’m considering going with dual electronic ignition. The plane has 4 switches which connect/activate the alternators and batteries to the main bus. FWIW, the plane is using an ACM from advanced and the EFIS has a backup battery as well.

For the purpose of this thread, lets IGNORE debate on:
1. Which ignition system is best
2. Why not just use a P-mags (which I am considering)

My main question is assuming I do dual electronic ignition that does NOT have its own power source, what is the best way to wire them into my plane? I’ve seen some cool setups that split the plane’s power into two halves with one ignition on each half which seems optimal, but this would require more switches, more solenoids, 3 more wires to the batteries in the back of the plane, another volt meter, and more complexity.
best-practices-06-1.jpg


Is there an easier way that is also robust? How about a battery isolator or some combination of diodes to the second battery to allow it to charge off the main bus but not go down if the main bus shorts?
 
I should add that either way I would plan on running fused wires from the electronic ignitions back directly to the two batteries (one for each).
 
Check out Fly EFII. they have a Buss manager that ties into the system for this exact application. I purchased one but an mot quite ready to install it yet.I also have their EFII System 32 purchased.
 
Thanks David. I have an email out to them to learn more about it. It's a bit of a black box and I'd like to understand the inner workings/logic used before I implement it.
 
SDSEFI CPI-2

If you use the CPI-2 automatic battery backup is included. No need to change your current electrical system. The backup battery will run until well after you exhaust the fuel.
 
Thanks McGraw. I was looking at that one this morning. Looks like a good option. So does that system run both ignitions off the main battery and switch both over to the backup battery if low voltage is encountered? Does it keep the backup battery charged?
 
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Thanks McGraw. I was looking at that one this morning. Looks like a good option. So does that system run both ignitions off the main battery and switch both over to the backup battery if low voltage is encountered? Does it keep the backup battery charged?

It does keep the backup battery charged, my understanding is it normally runs on the main battery. Please contact SDSefi.com for the most accurate information.

From the website the number is 403-671-4015. Also Ross Farnham advertises on this message board. .
 
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Thanks David. I have an email out to them to learn more about it. It's a bit of a black box and I'd like to understand the inner workings/logic used before I implement it.

Do a bit of a search and you will find at least one thread on VAF that performs a critical functions analysis of this particular "black box". May take some of the mystery out of it
 
Given you have dual batteries and dual alternators, simply wire the ignition feeds directly to separate batteries. Make the connection at the always-hot terminal of the master solenoid. Fuse it right there with a fusible link. Run two wires to the panel, add two toggles, IGN1 and IGN2. Run wires to the ignitions.
Done.
 
Given you have dual batteries and dual alternators, simply wire the ignition feeds directly to separate batteries. Make the connection at the always-hot terminal of the master solenoid. Fuse it right there with a fusible link. Run two wires to the panel, add two toggles, IGN1 and IGN2. Run wires to the ignitions.
Done.

This is the way.
 
Given you have dual batteries and dual alternators, simply wire the ignition feeds directly to separate batteries. Make the connection at the always-hot terminal of the master solenoid. Fuse it right there with a fusible link. Run two wires to the panel, add two toggles, IGN1 and IGN2. Run wires to the ignitions.
Done.

I'd add indicator lamps to indicate either having power - or not having power. I like DanH's idea but am concerned that the fusable link blows in flight and you have no idea you are now running on single ignition with single point of failure.

You could create a "no power indicator" as follows:

Power A ----->|-------/\/\/\/----->|------- Power B
................ rectifier resistor LED

Do not use a lamp, it could pass too much power into the other bus

If you have power at Ignition A, but not at B, the indicator will light.
Wire an identical circuit from B to A and you have the opposite situation covered
 
I'd add indicator lamps to indicate either having power - or not having power. I like DanH's idea but am concerned that the fusable link blows in flight and you have no idea you are now running on single ignition with single point of failure.

You could create a "no power indicator" as follows:

Power A ----->|-------/\/\/\/----->|------- Power B
................ rectifier resistor LED

Do not use a lamp, it could pass too much power into the other bus

If you have power at Ignition A, but not at B, the indicator will light.
Wire an identical circuit from B to A and you have the opposite situation covered

This has been a very common issue throughout the history of the two magneto system.

A a failure warning is a good idea.
 
Given you have dual batteries and dual alternators, simply wire the ignition feeds directly to separate batteries. Make the connection at the always-hot terminal of the master solenoid. Fuse it right there with a fusible link. Run two wires to the panel, add two toggles, IGN1 and IGN2. Run wires to the ignitions.
Done.

DanH this seems reasonable but if I only have one battery hooked up to the bus at a time only one battery is charging while both are draining since the alternators are both on the main bus. It would require me to remember to alternate batteries on the main bus every so often to keep them charged.

If I keep both batteries on the main bus then a short to the main bus could wipe out the ignition.

So it seems i would want to hook up battery #2 to the main bus with a diode in parallel to the solenoid for that battery such that it can accept current from the main bus but not be drained by the main bus?
 
I'm not really a fan of the EFII Bus manager because it routes your main (and essential) bus through standard through hole relays instead of using a firewall mount continuous duty contactor. To protect against essential bus relay fault a standard 30A switch is employed. Also, it's not really the right application for this as it's designed to manage fuel pumps for EFI, which isn't not needed for an EI only installation.

I won't dive into the black box nature of the EFII stuff or the unwillingness of the developer to explain what is going on, but for sure search around on the forums.

Anyway, back to EI and electrical systems there are basically two ways EI systems deal with this:

1. The EI system depends on you having a redundant power system.
2. The EI system has built in provisions to power itself in the case of a fault.

#1 is an option and if you go down that route, I'd do as Dan suggests and have two electrical systems independent of each other and run one ignition system per side.

#2 only has two products I'm aware of, pmag which has it's own built in power source, and SDS CPI-2 which has provisions to maintain it's own out of band backup battery.

There are for sure pros and cons to pmag or CPI2, but for me I'd pick the additional wiring for a crank trigger over continued inspections. YMMV.

In my airplane I'm looking at a hybrid approach. I plan to install a CPI2 then wire the secondary power wire to the secondary power system and disable the charging circuit. I posted about my plan here:

https://vansairforce.net/community/showpost.php?p=1560725&postcount=28

If you look closely, all of my critical avionics all provide dual input, so I just utilized that and have completely separate electrical systems with everything important attached to both.

One thing about my design (or using a pmag, or CPI2 with battery) is that there isn't any switch to flip during a failure. I like that much better than some essential bus alternate feed or bus cross feed switch.

Hope that helps,
schu
 
DanH this seems reasonable but if I only have one battery hooked up to the bus at a time only one battery is charging while both are draining since the alternators are both on the main bus. It would require me to remember to alternate batteries on the main bus every so often to keep them charged.

I assume you do that anyway.

Do remember the Big Picture. Only need enough battery power to complete the flight, duration doubles if running just one ignition, and ignition draws average roughly 1 amp. It doesn't take much battery.

So it seems i would want to hook up battery #2 to the main bus with a diode in parallel to the solenoid for that battery such that it can accept current from the main bus but not be drained by the main bus?

Feeding the aux battery with a diode is perfectly reasonable. I've been flying such a system, with a very small aux battery, for the last 300~400 hours.

I've wired in a small voltage monitor board (red, below) to alert if the aux battery is not being charged via the diode. Given you have two main batteries, I assume you already have some sort of voltage indication for the aux. Your system would sketch as below. I've left out the aux battery contactor.
-
 

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I'd add indicator lamps to indicate either having power - or not having power. I like DanH's idea but am concerned that the fusable link blows in flight and you have no idea you are now running on single ignition with single point of failure.

Actually, you would be running two ignitions. The aux battery would discharge via the ignition load eventually, but it would take a while. How long would depend the size of the battery. Here the OP seems to have two full size batteries, and ignitions average about 1 amp. If ignition duration exceeds fuel duration, we're good.

None of that negates your concern for an aux battery charge warning. I run a little monitor board, your approach is interesting, and the OP probably already has an aux battery indication.
 
Yes that’s it Dan. I don’t have a voltage readout for each battery currently, only for the main bus, but would add that as well.

I assume you do that anyway.

Do remember the Big Picture. Only need enough battery power to complete the flight, duration doubles if running just one ignition, and ignition draws average roughly 1 amp. It doesn't take much battery.



Feeding the aux battery with a diode is perfectly reasonable. I've been flying such a system, with a very small aux battery, for the last 300~400 hours.

I've wired in a small voltage monitor board (red, below) to alert if the aux battery is not being charged via the diode. Given you have two main batteries, I assume you already have some sort of voltage indication for the aux. Your system would sketch as below. I've left out the aux battery contactor.
-
 
Schu, thanks for the summary. That continued inspection Vs. Time to install a SDS or AFII ignition system is exactly what i‘m weighing. Seems for a new build the fully electronic way is not a big hassle. The wiring is fairly simple when everything is open. I‘m probably looking at 30-40 hours of work I’m guessing to run the needed wires, install all the boxes including panel modifications, and mount the magnets on a completed plane, vs. a few hours of work to slap new pMags on. The added yearly inspection is not that big of a burden relative to the SDS or EFII system install time.
 
Schu, thanks for the summary. That continued inspection Vs. Time to install a SDS or AFII ignition system is exactly what i‘m weighing. Seems for a new build the fully electronic way is not a big hassle. The wiring is fairly simple when everything is open. I‘m probably looking at 30-40 hours of work I’m guessing to run the needed wires, install all the boxes including panel modifications, and mount the magnets on a completed plane, vs. a few hours of work to slap new pMags on. The added yearly inspection is not that big of a burden relative to the SDS or EFII system install time.

Remember that SDS will give you the advance and let you program it yourself as well as give you a LOP button.

EFII is a black box. It's not entirely clear what they are doing.

That may or may not appeal to you. Some places in life I want a mac over windows, but in other places I'll for sure pick nikon over canon, but then with something new, I'll find myself back to wanting an icom over a yaesu.

In the airplane, I want to see what timing I'm putting in and have the flexibility to program it myself, but I absolutely don't want a series of switches that need to be flipped to recover from failure. If I have dual EI and have someone ferrying my airplane home I don't want to have to give them extensive electrical system training.

In my ship I'll simply say, "There are two electrical systems, they are shown in the dual voltage monitors in the G3x. If you have master alarm due to an alternator failure, the fan won't stop, simply pull out the emergency procedures card and go from there, you have plenty of time."

On the emergency card it will explain that there are two electrical systems with a block diagram of how things are wired.
 
Of the many good options available, I'm going with dual CPI2 from SDS. As I'm in crazy man building airplane in garage phase, I don't have operational experience to share only my research and plan. Attached is my preliminary schematic where you can see how I'm doing it with two batteries and two alternators. Haven't decided if I'll install the second alternator but likely. You could let CPI2 charge the backup battery if all that the backup battery is used for is CPI2 but I'm using backup battery to backup G3X and G5. Backup power was my main concern when looking beyond magnetos or PMAGs. CPI2 has redundant power feeds and automatically switches to backup as needed. You can diode high select from multiple power sources and use any electronic ignition but CPI2 from SDS has that covered, includes LOP shift and the quality of build is very impressive.
 

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A hard ground fault inside one of the avionics could blow not only its own fuse,
but also the avionics master fuse. It is not a good idea to have two fuses in series.
 
Surefly

I have two Surefly (TSO) electronic ignitions.
They are powered directly from two different batteries. Each has a 10 A fuse.
They are installed per the manual and always powered. (no switches).
Current consumption is micro-amperes when the standard ACS ignition switch
is in the off position. About 0,5 A each when running. (IO-360).
Voltmeter on each battery.
The Surefly ignition operates and can be tested with ACS ignition switch in
the same way as a standard magneto.
If you prefer, remove the ACS ignition switch and install separate grounding
switches for each Surefly ignition. Then there is no single point of failure
left at all.
 
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