What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Single Alt Dual Battery System Design

bigwheel

Member
Hi everybody, new guy here. Been lurking on VAF for a few years after finding lots of the information I was seeking could be found here. Up till this point I've been able to find everything I've been looking for in existing threads. Unfortunately this time I have a specific question and I couldn't find a existing thread I felt it was appropriate to tag on to.

Hoping you guys will take a look at my power supply schematic and tell me its flaws. I have Bob Nuckolls book, which is full of great information, and I have read the pertinent parts several times. Because my plane will be fairly basic I want a simple yet robust electric system. So please, tell me what you think.



I should mention: This is a VFR only plane with a GRT Sport EX, airspeed and altimeter steam gauges.
 
Last edited:
John,

Some thoughts:
- Your use of two master solenoids and two batteries eliminates one "single failure takes out the world" risk. I don't know what your "voltage sensing relay" is supposed to do but if you are thinking of an automatic way to isolate a fault, this might not be it.
- Now that you have two master solenoids, you have twice the dead weight of the current draw from these solenoids. Some of these draw 3 amp to remain closed. So at up to 6 amps of current draw, you have created a load larger than most panel items. There is no way to avoid using two master solenoids (and still retain the needed robustness of design) as you need the engine start current capacity. What you don't need is these solenoids sucking up current to just provide power to you panel when the alternator dies. You need smaller, 30 amp or so relays to feed your panel (typical current draw to hold shut is 100 ma). That why when the alternator dies you open both master solenoids to drop that load. If you also power the typical loads that you would dump for a loss of alternator (landing lights, strobes, boost pump, pitot heat, etc.) from the output of the master solenoids, when you open the solenoids when the alternator dies you drop the load to what you really want - so you enhance your electrical reserve. If you need one of these loads (like boost pump for landing) you just shut one of the master solenoids when you want the load.
- Once you decide to have these independent feeds to your panel, you can now enhance your redundancy by splitting your panel so that half runs on each battery (e.g. Comm#1 and Nav #1 on #1 battery, Comm #2 and Nav #2 running on #2 battery. This way if you have a battery fault you can feed the panel via the other battery.

If you send me your email I'll send you what I did.

Carl
 
Jon, welcome aboard the good ship VAF:D
Thanks Mike!

John,

Some thoughts:
- Your use of two master solenoids and two batteries eliminates one "single failure takes out the world" risk. I don't know what your "voltage sensing relay" is supposed to do but if you are thinking of an automatic way to isolate a fault, this might not be it.
- Now that you have two master solenoids, you have twice the dead weight of the current draw from these solenoids. Some of these draw 3 amp to remain closed. So at up to 6 amps of current draw, you have created a load larger than most panel items. There is no way to avoid using two master solenoids (and still retain the needed robustness of design) as you need the engine start current capacity. What you don't need is these solenoids sucking up current to just provide power to you panel when the alternator dies. You need smaller, 30 amp or so relays to feed your panel (typical current draw to hold shut is 100 ma). That why when the alternator dies you open both master solenoids to drop that load. If you also power the typical loads that you would dump for a loss of alternator (landing lights, strobes, boost pump, pitot heat, etc.) from the output of the master solenoids, when you open the solenoids when the alternator dies you drop the load to what you really want - so you enhance your electrical reserve. If you need one of these loads (like boost pump for landing) you just shut one of the master solenoids when you want the load.
- Once you decide to have these independent feeds to your panel, you can now enhance your redundancy by splitting your panel so that half runs on each battery (e.g. Comm#1 and Nav #1 on #1 battery, Comm #2 and Nav #2 running on #2 battery. This way if you have a battery fault you can feed the panel via the other battery.

If you send me your email I'll send you what I did.

Carl

The VSR is used to ensure batt1 is fully charged before allowing the alternator to begin charging batt2. The the engine is shutoff the batteries are again isolated. Here is an example of a VSR

I hadn't considered the draw of the contractors. I looked up some and found that there are continuous duty contractors available that draw 0.7A. That's still nothing to shrug off.

Points well taken. Thanks Carl.
 
I read the diagram differently.

If only one battery is connected to the Power Bus at a time then the current drawn by the contactors is identical to the usual one alt./one batt. system.

If your EMS can monitor two voltages simultaneously then it would be a good electric source backup with an easy indication of its status.
 
As shown, battery 1 seems to be used for starting the engine. If batt 2 is also used as an alternate start battery, the wiring to and from the power buss has to carry the starter current load------as does the power buss-----which I suspect is not how you intend to do things. If you want to use battery 2 as an alternate power source for the starter, you might consider adding the needed wiring.

If batt 2 is only there for backup to the electrical load of the panel, and not to be a backup to the starter, then IMHO you do not need a second contactor. Just a switch will do the job just fine.

This is how I wired my plane, the backup battery is run through a DPST switch which is rated to carry the need load on each set of contacts, but I paralleled them for extra robustness, and in case one set of contacts failed.

Do you have a low voltage alarm to let you know to turn on the backup battery if the main battery goes TU??? Or, do you plan to run both batteries at the same time, and let the one with the highest power do the work?? If the latter, consider putting in blocking diodes so the good battery will not back feed to the weak battery.

Also, when using a VSR, and having the main battery go way low in voltage so that you have to engage the backup battery----------will the backup battery be taken off the charge due to the VSR sending all the current to the bad battery?? If so, you are running on borrowed time with the backup battery as it is now a total loss system.
 
Last edited:
Thanks Mike!



The VSR is used to ensure batt1 is fully charged before allowing the alternator to begin charging batt2. The the engine is shutoff the batteries are again isolated. Here is an example of a VSR

/QUOTE]

I offer the VSR is not required or desired. This adds an unnecessary failure point. Use two identical batteries (e.g. PC-625) and have them in parallel for normal operations (including charge and engine start). Split them if the alternator fails.

Batteries will charge based on internal voltage (terminal voltage minus the voltage drop from the battery's internal resistance). As such, the battery that has the lowest internal voltage will always take the most charge current - until the battery internal voltages are the same.

Carl
 
I read the diagram differently.

If only one battery is connected to the Power Bus at a time then the current drawn by the contactors is identical to the usual one alt./one batt. system.

If your EMS can monitor two voltages simultaneously then it would be a good electric source backup with an easy indication of its status.
I'm not sure if the GRT can monitor two different voltage sources simultaneously.

As shown, battery 1 seems to be used for starting the engine. If batt 2 is also used as an alternate start battery, the wiring to and from the power buss has to carry the starter current load------as does the power buss-----which I suspect is not how you intend to do things. If you want to use battery 2 as an alternate power source for the starter, you might consider adding the needed wiring.

If batt 2 is only there for backup to the electrical load of the panel, and not to be a backup to the starter, then IMHO you do not need a second contactor. Just a switch will do the job just fine.

This is how I wired my plane, the backup battery is run through a DPST switch which is rated to carry the need load on each set of contacts, but I paralleled them for extra robustness, and in case one set of contacts failed.

Do you have a low voltage alarm to let you know to turn on the backup battery if the main battery goes TU??? Or, do you plan to run both batteries at the same time, and let the one with the highest power do the work?? If the latter, consider putting in blocking diodes so the good battery will not back feed to the weak battery.

Also, when using a VSR, and having the main battery go way low in voltage so that you have to engage the backup battery----------will the backup battery be taken off the charge due to the VSR sending all the current to the bad battery?? If so, you are running on borrowed time with the backup battery as it is now a total loss system.

I do intend to use batt2 as a backup start battery. If leads from batt1 and batt2 connect to the same lug on the buss then the buss won't have to carry any load. But I am working on a schematic that may work better, don't know yet though.

The GRT has a built in low voltage alarm. I do not plan to run the batteries at the same time; when batt1 gets low I'll switch to batt2.

Your last point about the VSR is well taken. I need to investigate this further. Only reason I could see the main battery go way low with a working alternator is if it fails. If it fails and the alternator keeps the voltage above 13.3VDC then the VSR will keep the batteries connected. What that will do to batt2 I'm not sure but I imagine it wouldn't be good.
 
I do intend to use batt2 as a backup start battery. If leads from batt1 and batt2 connect to the same lug on the buss then the buss won't have to carry any load. But I am working on a schematic that may work better, don't know yet though.

This requires big fat wires going to the buss from each battery----as drawn.

I do not plan to run the batteries at the same time; when batt1 gets low I'll switch to batt2.

How do you plan to switch in batt 2?? Do you intend to switch off batt 1 when you engage batt 2??

A DPST switch could do that, but I would suggest you make sure it is a "Make before Break" switch, otherwise the EFIS and other goodies most likely will need to reset after switching power.

If using separate switches for swapping battery feeds, be sure to have a way to disable any back feed from the good battery to the bad one. Either a diode or a warning light------wired correctly a pair of DPDT switches can activate a warning light when the backup battery is engaged, and turn it off when the main batt is then disconnected.
 
[/URL]
I offer the VSR is not required or desired. This adds an unnecessary failure point. Use two identical batteries (e.g. PC-625) and have them in parallel for normal operations (including charge and engine start). Split them if the alternator fails.

Batteries will charge based on internal voltage (terminal voltage minus the voltage drop from the battery's internal resistance). As such, the battery that has the lowest internal voltage will always take the most charge current - until the battery internal voltages are the same.

Carl
I will give some more thought to paralleling the batteries. When I evaluated this in the beginning I decided I'd like to keep my batteries isolated from each other but I didn't write the the why's. It is possible, even likely, that a VSR isn't the right component to use. I had planed on using an old school diode isolator because they maintain isolation between the batteries at all times but they burn up several amps to operate. This means the batteries aren't seeing their intended charging voltage.
 
This requires big fat wires going to the buss from each battery----as drawn.



How do you plan to switch in batt 2?? Do you intend to switch off batt 1 when you engage batt 2??

A DPST switch could do that, but I would suggest you make sure it is a "Make before Break" switch, otherwise the EFIS and other goodies most likely will need to reset after switching power.

If using separate switches for swapping battery feeds, be sure to have a way to disable any back feed from the good battery to the bad one. Either a diode or a warning light------wired correctly a pair of DPDT switches can activate a warning light when the backup battery is engaged, and turn it off when the main batt is then disconnected.

You guys are providing too much feedback...I can't keep up:)

These big fat wires only have to be #3AWG and aren't that long but yes, you are correct.

My switching method was simply: batt1 down to some low voltage, batt2 on, batt1 off. That half second of both switches on going to kill batt2?
 
I think the diode "OR" would take care of the higher voltage battery supplying your load without any user intervention. The battery charge path would need to be through some other mechanism if you want to be able to isolate the batteries and their charge paths. In general though you want to be able to use every bit of available battery capacity even if the battery is "bad".

I'm planning to use a battery "OR" made from MOSFETs that I built. Its still in the proto stage at this point, but that part of the circuit works great. The FET "OR" works like the diode "OR" but it doesn't have the associated voltage drop and power/thermal issues that have to be dealt with. I also put a battery charger for my AUX gel cell battery as part of that circuit and it's still running a little warm for my satisfaction. I don't really need this circuit yet since I'm still building my fuse so debugging is pretty far down on my list at the moment.
 
I'm not sure if the GRT can monitor two different voltage sources simultaneously.

It may depend on what pieces from GRT you are speaking of.

I am not intimately familiar with the newest offerings. I am familiar with the EIS.

If you are speaking of a system that includes an EIS engine monitor, then yes it can monitor multiple anythings. It has a "standard" voltage readout that is taken from the EIS +V power input itself. For the second display, there are a number of 0-5 volt auxiliary inputs that could be used via construction of a voltage divider and then programming the appropriate y=mx+b values into the EIS to show the secondary voltage.
 
Let's look at the big picture. Why a dual battery system? Is the engine electrically dependent? What kind of engine is it? If not for the engine, then are two batteries intended for the avionics? Since this is a VFR aircraft, a backup to a backup is not needed. One larger battery is lighter and weighs less and is less complicated than two batteries. If the alternator fails, the battery is the backup. Another backup is not needed and it just adds weight. Bob Nuckolls' book mentions load testing a battery periodically to make sure that it has enough stored energy to power essential equipment for the desired time. He has also stated that the battery is very reliable, not any more likely to sudenly fail than prop bolts.
A small brownout battery might be desired to prevent avionics from rebooting during engine start. Brownout/avionics backup circuit.
 
Contactor current draw

was of interest to me. I measured the current draw on the master and the starter contractors, both B & C products. The master contractor required .8 amps, the starter contractor a whooping 1.75 amps.

If a .8 amp draw on a system during an emergency is "too" much, then I posit that you have too much stuff running. I know, it is a relative thing.
 
If a .8 amp draw on a system during an emergency is "too" much, then I posit that you have too much stuff running. I know, it is a relative thing.

Agreed.

Take a look at his schematic------the exact load is imposed on the buss no matter which battery is supplying the power. No automatic load shedding when going to the backup battery.

IMHO, a better setup would be an essential buss powered directly from the back up battery, as well as through a Schotkky diode off the main buss (which is powered by the main battery). With this setup, the items on the e/buss will get their power off the main battery, or off the backup. But the non essential items will not suck current during a failure of the main system.

I have almost the exact setup in my 10, only difference is I also have a backup alternator and not a VSR. I run both main and aux power all the time so there is no need to turn on the aux power, it just simply and seamlessly comes up as needed. Added benefit is that I power up the EFIS on the aux, then start the engine on the main-------and do not loose/brownout the EFIS at startup.
 
I think the diode "OR" would take care of the higher voltage battery supplying your load without any user intervention. The battery charge path would need to be through some other mechanism if you want to be able to isolate the batteries and their charge paths. In general though you want to be able to use every bit of available battery capacity even if the battery is "bad".

I'm planning to use a battery "OR" made from MOSFETs that I built. Its still in the proto stage at this point, but that part of the circuit works great. The FET "OR" works like the diode "OR" but it doesn't have the associated voltage drop and power/thermal issues that have to be dealt with. I also put a battery charger for my AUX gel cell battery as part of that circuit and it's still running a little warm for my satisfaction. I don't really need this circuit yet since I'm still building my fuse so debugging is pretty far down on my list at the moment.
Automatic switching is not a priority but ensuring that a fault in one part of the system does not damage the rest of the system is. Your obviously much more knowledgeable about electrons and the means to control them.

It may depend on what pieces from GRT you are speaking of.

I am not intimately familiar with the newest offerings. I am familiar with the EIS.

If you are speaking of a system that includes an EIS engine monitor, then yes it can monitor multiple anythings. It has a "standard" voltage readout that is taken from the EIS +V power input itself. For the second display, there are a number of 0-5 volt auxiliary inputs that could be used via construction of a voltage divider and then programming the appropriate y=mx+b values into the EIS to show the secondary voltage.
I'm planing to use the GRT Sport EX and their EIS so it sounds like I'll have the ability to monitor the voltage of both batteries.

Let's look at the big picture. Why a dual battery system? Is the engine electrically dependent? What kind of engine is it? If not for the engine, then are two batteries intended for the avionics? Since this is a VFR aircraft, a backup to a backup is not needed. One larger battery is lighter and weighs less and is less complicated than two batteries. If the alternator fails, the battery is the backup. Another backup is not needed and it just adds weight. Bob Nuckolls' book mentions load testing a battery periodically to make sure that it has enough stored energy to power essential equipment for the desired time. He has also stated that the battery is very reliable, not any more likely to sudenly fail than prop bolts.
A small brownout battery might be desired to prevent avionics from rebooting during engine start. Brownout/avionics backup circuit.
I had hoped to avoid this question; not because it isn't valid but because it has been evaluated already. For my mission I'd like my plane to have dual batteries.

was of interest to me. I measured the current draw on the master and the starter contractors, both B & C products. The master contractor required .8 amps, the starter contractor a whooping 1.75 amps.

If a .8 amp draw on a system during an emergency is "too" much, then I posit that you have too much stuff running. I know, it is a relative thing.
Cool. Thanks for those numbers. I agree that .8A isn't much but it could be the difference between having the power to turn on the runway lights and not.

Agreed.

Take a look at his schematic------the exact load is imposed on the buss no matter which battery is supplying the power. No automatic load shedding when going to the backup battery.

IMHO, a better setup would be an essential buss powered directly from the back up battery, as well as through a Schotkky diode off the main buss (which is powered by the main battery). With this setup, the items on the e/buss will get their power off the main battery, or off the backup. But the non essential items will not suck current during a failure of the main system.

I have almost the exact setup in my 10, only difference is I also have a backup alternator and not a VSR. I run both main and aux power all the time so there is no need to turn on the aux power, it just simply and seamlessly comes up as needed. Added benefit is that I power up the EFIS on the aux, then start the engine on the main-------and do not loose/brownout the EFIS at startup.
With a simple plane such as mine I don't see a need for automatic load shedding but I can certainly see the value. I also see value in being able to turn on various things that may or may not end up being essential in a particular situation.

I see that I have some issues with my current schematic so I will go back and re look at things while keeping what you guys have said in mind. I'm trying to find the right balance between system function and component count. Big thanks everybody! I'll post up my next revision when I get it done.
 
Last edited:
I planning much the same for my -8 and look fwd to your next revision. Mine will be a VFR, dual EI airplane also with dual batteries. And I want to keep the system simple too.
 
it works fine

I have wired several planes exactly the way it is shown in the original post.
Basically, the two batteries wired in parallel, are only combined when the 2nd master switch is engaged. This can be done if you need extra power to start in the event the main battery gets low. Actually, either battery can serve as the main battery.
In my application, I use the battery behind Mstr 2 to power the Essential Bus to run the EFIS before start up, but it can also function as main power when needed by turning on Mstr 2.
Additionally, I installed a diode between the Ess Bus and the 2nd battery so that it continually gets charged from the system when the alternator is running.
If you use two Shorai batteries, they will both fit in the same battery tray that VANs provides for the rear battery in an RV8.
 
I have essentially the same system without the VSR.
2 identical batteries always on for all flight operations including engine start.
With identical batteries your charging problem is largely solved and I see no need for a VSR.
Each battery voltage condition can be independently verified before start if you
wish to do so and can be turned off for any reason without affecting operations.
I use 2x18Amp hour panasonic or equivalent sealed lead acid batteries available at ACE hardware for 45$ replaced every 5 years (just because)
and have seen no electrical issues in 10 years and 900 hours of RV flying.
Most systems are way more complex than what you propose and essentially the same as mine.
 
I planning much the same for my -8 and look fwd to your next revision. Mine will be a VFR, dual EI airplane also with dual batteries. And I want to keep the system simple too.
I hope the whatever schematic I develop will be of help to you but I'll pretty old school and don't mind flipping switches rather than having things be automatic.

I have wired several planes exactly the way it is shown in the original post.
Basically, the two batteries wired in parallel, are only combined when the 2nd master switch is engaged. This can be done if you need extra power to start in the event the main battery gets low. Actually, either battery can serve as the main battery.
In my application, I use the battery behind Mstr 2 to power the Essential Bus to run the EFIS before start up, but it can also function as main power when needed by turning on Mstr 2.
Additionally, I installed a diode between the Ess Bus and the 2nd battery so that it continually gets charged from the system when the alternator is running.
If you use two Shorai batteries, they will both fit in the same battery tray that VANs provides for the rear battery in an RV8.
Thanks for the ideas. I think having batt2 power the EFIS during startup is a good idea.

Just curious, why do you need a backup start battery?
In case the main battery is dead;) I don't have enough experience to know how hand propping a fuel injected engine would go and I'd prefer to not find out.

I have essentially the same system without the VSR.
2 identical batteries always on for all flight operations including engine start.
With identical batteries your charging problem is largely solved and I see no need for a VSR.
Each battery voltage condition can be independently verified before start if you
wish to do so and can be turned off for any reason without affecting operations.
I use 2x18Amp hour panasonic or equivalent sealed lead acid batteries available at ACE hardware for 45$ replaced every 5 years (just because)
and have seen no electrical issues in 10 years and 900 hours of RV flying.
Most systems are way more complex than what you propose and essentially the same as mine.
I agree that with identical batteries a charge controller is not needed but the batteries need to be the same; same type, same brand, same model, same age. So if one battery suffers infant mortality then do you replace both? Or install some kind of charge controller then the battery only have to be the same type.

I think parallel batteries should have diodes between them on the charging leg to prevent one draining the other. Is two diodes more or less reliable than a VSR?
 
In case the main battery is dead;) I don't have enough experience to know how hand propping a fuel injected engine would go and I'd prefer to not find out.

I'm with you there. However it seems like if you don't need the second battery for redundancy then its just dead weight most of the time (along with its contactor and cable). If on the other hand you do need it for redundancy are you really going to want to take off with it dead?

There are other ways to deal with the dead battery problem; for example some people leave their strobe/beacon switch on so that they'll be reminded if they forget to turn off the master.

I like the backup battery idea (I have one on my plane), just not sure it needs to be as big as the main battery or that you need the current draw of another contactor?
 
Your absolutely right, if my only reason was for a backup start battery then I would make much more sense to carry one of those pocket jump packs. Since I also want some redundancy for night VFR which I do a fair amount of.

If I had a dead battery for a known reason that reason wasn't a safety of flight issue (left master on, excessive cranking because of a hot start issue, etc) then yes I'd takeoff with one dead battery as long as the alternator was showing a charge.
 
Your absolutely right, if my only reason was for a backup start battery then I would make much more sense to carry one of those pocket jump packs. Since I also want some redundancy for night VFR which I do a fair amount of.

If I had a dead battery for a known reason that reason wasn't a safety of flight issue (left master on, excessive cranking because of a hot start issue, etc) then yes I'd takeoff with one dead battery as long as the alternator was showing a charge.


That seems to make sense, assuming you're flying in daylight.

My backup battery is there because I've got dual Lightspeed electronic ignition. I check it during run-up and it would be a no-go item if not working (perhaps an excess of caution).
 
There are several misconceptions about batteries in this thread. To support my opinion, I posted on the AeroElectric List. You can read Bob Nuckolls' reply HERE.
Lead acid batteries connected in parallel do not need to be the same in any respect. Even a fully charged battery will not discharge into a fully discharged battery in any significant amount. Diodes or other isolation is not required. The exception would be in the case of a battery with a shorted cell.
Even batteries of different chemistry (lead acid and Lithium) may be connected in parallel while being charged by an alternator. How would each battery even know that the other battery was connected? Each battery only sees the alternator voltage, not the voltage of the other battery. I agree that batteries of different chemistry should not be connected in parallel when not being charged by an alternator.
 
Thanks for asking Bob the battery question. He is obviously very knowledgeable with this stuff and I appreciate he's willingness to share that knowledge. Unfortunately my life experience has skewed my perspective and I have a hard time going against those experiences. I'll likely be installing some sort of battery isolator because that is what will make me comfortable.
 
Last edited:
I can not argue with your reasoning. For most of us, airplanes are our toys. We wire them and equip them to meet our personal goals and desires, which are different for each of us.
 
I've decided to install electronic ignition (CPI) so I needed to rethink my electrical system and you guys gave me great feedback last time. This is where I'm at currently but I'm still nerding over it.

34313569460_0d2726e950_b.jpg
\

I can not bring myself to simply parallel the batteries so I'm still thinking I'd like to use a battery idolator of some sort.

I know...the diode is oriented backwards...oops.
 
Alternator contactor?

Don't think you really need an alternator contactor or battery isolator. You do want an ANL to protect the alternator and B lead from the batteries. After the ANL, it should connect to the buss side of one of your battery contactors and a fat jumper over to the other contactor. An alternator contactor will cost you about an amp and gives you nothing you don't already have.

You say you are concerned about paralleling the batteries. Don't be. Lead acid batteries will not discharge each other, especially when the alternator is charging both of them at something over 14 volts. Each battery will only take as much charge as it is capable of so you don't need to charge one first before you charge the other. They take care of that themselves.

If you have an alternator failure, pull the field breaker and motor on. You can open one of the contactors to save that battery for later or, better yet, open both contactors and feed your e-buss through switches from either battery. You might also consider feeding your ignitions directly from the batteries, one from each. I personally dislike the idea of feeding both ignitions from one source. You don't want one failure to take out both of them at once.

Breaker/switches may seem to save you a component, but are not known for reliability. Consider breakers (or fuses) and switches.

Good luck,

Ed Holyoke




I've decided to install electronic ignition (CPI) so I needed to rethink my electrical system and you guys gave me great feedback last time. This is where I'm at currently but I'm still nerding over it.

34313569460_0d2726e950_b.jpg
\

I can not bring myself to simply parallel the batteries so I'm still thinking I'd like to use a battery idolator of some sort.

I know...the diode is oriented backwards...oops.
 
Here is what I use between my two batteries. It has worked flawlessly for 4 years. It will only connect the two batteries together when either one of them is over 13 + volts (being charged) and will not connect the two batteries if one of the batteries voltage is to low (I believe 8 volts). The specs are here.. https://www.bluesea.com/products/old/7600 It also has state output which can be displayed on your EFIS
 
Thank you for the thoughts so far.

I'm a fan of breaker switches and had great service from the ones I installed in a previous project.

The alternator contractor was there from a previous revision and I failed to removed it. I'll follow the manufacture recommendation when I install the alternator.

I agree on the ignitions. Currently they could be powered from either battery but there's too many components and connections in there now.

Bill, I have been considering the Blue Sea ACR as it is very popular in the marine world.
 
Here is another design I have been thinking about. And since ya'll now know I'm building a Bearhawk I'll include some more background info.

My airplane will draw approximately 21A with everything on. Has an electrically dependent engine (SDS CPI ignition). Will be flown at night. Will have a GRT Sport usually displaying engine instruments and a tablet wirelessly connected to the sport to display flight instruments. Single alternator (B&C 30A permanent magnet I hope) and dual battery (PC680). I'll be using fuses and only install switches on equipment that doesn't have built in on/off switching.

36991914770_ac4d7b69d8_b.jpg


This design significantly reduces the parts count, eliminates waste power consumption, should be very reliable and is very simple. It does require longer runs of heavy cables (approximately 4' is the longest). The Perko switch can be mounted in the pilot side kick panel which will be accessible during flight.
 
Back
Top