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Dual Battery Installation RV-7(A) RV-9(A)

terrye

Well Known Member
I'm using the Aeroelectric Z-14 architecture with dual PC-680 batteries mounted on the firewall of my RV-9A. The second battery will be mounted on the pilot side at the same waterline as the primary battery. My engine is an IO-320 with a constant speed prop. Alternators are 60A B&C primary and 20/30A B&C backup (vacuum pump pad mounted).

I recall pictures of dual firewall mounted batteries, but after an extensive search on this site was unable to find any or they have been deleted.

I'd appreciate any pictures of the second battery, battery box, battery contactor and cross tie contactor, and battery wiring to the contactors. Any advice also appreciated.
 
Howdy,

I put 2 680s in my 6, the second aft of the firewall where the std position is for the 6. No reason not to put it on the firewall, though it gets busy there. You might want to look at where your oil cooler is going to go and make sure you've got the space. If oil cooler on baffles, you might be dumping hot air on the battery. Another consideration might be CG, with extra battery weight forward, a second alternator, and a heavy prop.

I didn't use a 3rd cross-tie contactor. I have a battery contactor on each and a fusible link protected wire to the E-bus from each. The two contactors are joined with a heavy wire going through a firewall penetration. The front one is connected to the start contactor with a copper bar. I have two batt switches, Off-E-buss-On. My original thinking was to use batt 1 for starting while batt 2 powered the E-bus to prevent brownout. That turned out to not be necessary and I found out that batt 2 would try and charge itself though the E-bus as soon as the alternator came on line before I threw the switch to put it on the main bus. I blew a couple of fuses before I figured that out. Nowadays I just turn both batteries on for starting.

I'm wondering why you need 2 alternators at all if you are going to have 2 batteries. I considered having 1 battery and 2 alternators but I wanted to have independent sources for my dual electronic ignitions. I think that sometimes we provide too many backups for backups. ;-)

Ed
 
I'm wondering why you need 2 alternators at all if you are going to have 2 batteries. I considered having 1 battery and 2 alternators but I wanted to have independent sources for my dual electronic ignitions. I think that sometimes we provide too many backups for backups. ;-)

Ed
I read Bob Nuckolls' Aeroelectric Connection book and evaluated his Z-xx architectures against my mission requirements which include IFR. His Z-12 Single Battery, Dual Alternator would probably work just as well, but my panel builder recommended a backup battery for the EFIS. The backup battery was about 4x the cost and 1/4x the weight of the PC-680. I decided that if I was stranded somewhere I'd rather have dual PC-680s.

But you're right. As EAB aircraft builders we have perhaps too many choices for backups. My C-150 has a single alternator, single battery, but I wouldn't fly IFR in it:)
 
Dual Battery Installation RV-7A

Hi Terry, I have the exact installation you are speaking of. I have some photos of my firewall where I have my two batteries installed. Photobucket is no longer working for me to post pictures. If you can give me an email address i?d Be glad to send them.

Or email me at terry Dot mortimore at algoma dot com


Terry
 
Dual Batteries

Terry, I would be interested in seeing the pics of your dual battery installation.
Please send to d dot rohrer at twc dot com. Thanks.
 
Terry Mortimore dual battery photos RV-6A

Ref posts #4 and #8 in this thread.

Terry Mortimore's dual battery photos are shown below and are in the google photo album here https://photos.app.goo.gl/oRyKLG3i4AHxUGWE7

Terry has RV-6A with EFII which uses SDS ECU. As an aside, do not assume EFII and SDS are wired identically.

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Here are a few photos I have of my dual battery installation on my RV-9A. I fabricated up a couple custom size boxes for Lithium Ion batteries. With the added weight of everything required for a dual battery install on the firewall, the heavier C/S three blade MT prop, and the Anti-Splat Nose Job bar, SS and fiberfrax firewall fire-stop, I wanted to lighten up on other things FWF, so LI batteries for me. I had dual batteries with two masters and contactors on the RV-10 and the second battery got me home when my alternator gave up 100 miles from home. Right now I have a 40 amp relay that is hard wired to the battery with a fusible link to feed an essential buss for the avionics but am re-thinking that. I will probably do away with the E buss and load shed by switches if needed. My E buss was going to be diode protected to prevent shut down of the avionics during engine starting, but I have since decided on adding a GAD-27 and that will take care of that for me. No schematic for you but simple architecture. Pilot side battery is main battery. I can use either the left, right, or both as desired for starting and accessories.
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[/url]DSC02267 by David C, on Flickr[/IMG]
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[/url]DSC02266 by David C, on Flickr[/IMG]
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[/url]DSC02265 by David C, on Flickr[/IMG]
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[/url]DSC02264 by David C, on Flickr[/IMG]
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[/url]DSC02263 by David C, on Flickr[/IMG]
 
Dual Battery Installation RV-7A

When my pictures get posted you?ll see that I used batteries from summit racing.

https://www.summitracing.com/int/parts/xsp-s680/overview/

With these battery boxes, which I lightened up, if you lay them out well you can catch the angle X bracing on the back side of the firewall.

https://www.summitracing.com/int/parts/xsp-512

You will see that I used 1/8 X 1 inch copper flat bar to join all the battery contactors together.

I have the Dual EFII injection and ignition system, my electrical system has been bullet proof in the 190 hours I have put on my RV-6A in the last 14 months.

Cheers, Terry
 
Thanks for the responses so far. Still interested in additional pictures especially the battery installation on the pilot's side and potential interference with the oil cooler.
 
How much is enough?

I fly professionally and do regularly fly my -10 IFR. If I have an alternator failure, then I have a couple hours of main battery to get on the ground. That equates to about 300 NM plus time for an approach. How often do any pilots here fly where there is no airport within a 300 NM radius that is above minimums?

If I am concerned about having power to run my full EFIS and coupled autopilot for an approach, I can power down the battery master, fly using my G5?s four hour battery, navigating to an IAF with my IPad, then power up and have almost all the main battery left.

Dual alternators and dual batteries? Are we talking oceanic crossings here? Hey it is up to you to decide what level of redundance you are comfortable with but I suggest that if you need hours and hours of battery or multiple generators before you have to use the hours and hours of battery, you should have a second Lycoming.
 
Terrye,

I have two batteries installed. The picture below shows the location of the pilot's side battery box. This is an old picture before the rest of the hardware was installed. I did leave enough room on top of the battery box so that the battery can be slid straight up and out. It is not even close to the oil cooler. This weekend I will post the later pictures with everything installed on my web site below. These pictures are in the engine folder.

FP29042017A00035.jpg


Paul
 
I fly professionally and do regularly fly my -10 IFR. If I have an alternator failure, then I have a couple hours of main battery to get on the ground. That equates to about 300 NM plus time for an approach. How often do any pilots here fly where there is no airport within a 300 NM radius that is above minimums?

If I am concerned about having power to run my full EFIS and coupled autopilot for an approach, I can power down the battery master, fly using my G5?s four hour battery, navigating to an IAF with my IPad, then power up and have almost all the main battery left.

Dual alternators and dual batteries? Are we talking oceanic crossings here? Hey it is up to you to decide what level of redundance you are comfortable with but I suggest that if you need hours and hours of battery or multiple generators before you have to use the hours and hours of battery, you should have a second Lycoming.

I?ve posted on this in the past so for those readers who track such stuff, please be tolerant.

Mark,

I offer that the single failure mode (loss of the alternator) that you address is not the foundation to design any IFR power distribution scheme. The simple example is a twin aircraft with two alternators and two batteries that experienced total electrical failure from a single high resistance contact failing. For IFR I offer a thoughtful examination of ?what would happen if? any component, wire or connection failed is mandatory. Do you loose everything or does the panel ?gracefully decline?? Stuff will break - decide if you can live with the results. If not, then sharpen your pencil.

After a lot of study a few observations become evident to me for IFR power designs:
- A standy alternator provides risk mitigation for only one failure mode, the loss of the primary alternator. The loss of the primary alternator is not the limiting failure mode.
- Two batteries and single alternator (with thoughtful design) provides superior fault tolerance capability compared to one battery and two alternators.
- Continued IFR flight must be maintained with no pilot action following a fault. If time is available then full panel restoration may be done with a simple pilot action if this does not distract the pilot from flying the plane. Here digging into a flight bag for an iPad to get you on the ground in IMC would not be an acceptable mitigation.

There are many ways to achieve this, some simple and some overly complex. If interested in how I do this PM me your email address and I?ll send details.

Carl
 
I fly professionally and do regularly fly my -10 IFR. If I have an alternator failure, then I have a couple hours of main battery to get on the ground. That equates to about 300 NM plus time for an approach. How often do any pilots here fly where there is no airport within a 300 NM radius that is above minimums?

If I am concerned about having power to run my full EFIS and coupled autopilot for an approach, I can power down the battery master, fly using my G5?s four hour battery, navigating to an IAF with my IPad, then power up and have almost all the main battery left.

Dual alternators and dual batteries? Are we talking oceanic crossings here? Hey it is up to you to decide what level of redundance you are comfortable with but I suggest that if you need hours and hours of battery or multiple generators before you have to use the hours and hours of battery, you should have a second Lycoming.

When I made the decision to use a dual alternator dual battery system (architecture by Bob Nuckolls Aeroelectric Connection) I considered the following:
1. Airports in Canada are much further apart than in the US
2. British Columbia has 3 major high mountain ranges running north/south
3. All the current single engine airplanes, Cirrus, Cessna 350/400, Bonanza, Mooney in production use this type of architecture.
Since I can't afford any of the current production single engine airplanes, I decided I could at least make the electrical system as reliable and as redundant and as safe.
 
When I made the decision to use a dual alternator dual battery system (architecture by Bob Nuckolls Aeroelectric Connection) I considered the following:
1. Airports in Canada are much further apart than in the US
2. British Columbia has 3 major high mountain ranges running north/south
3. All the current single engine airplanes, Cirrus, Cessna 350/400, Bonanza, Mooney in production use this type of architecture.
Since I can't afford any of the current production single engine airplanes, I decided I could at least make the electrical system as reliable and as redundant and as safe.

Terry,

Are you using lithium batteries or lead acid in your setup?
 
I'm using the Aeroelectric Z-14 architecture with dual PC-680 batteries mounted on the firewall of my RV-9A. The second battery will be mounted on the pilot side at the same waterline as the primary battery. My engine is an IO-320 with a constant speed prop. Alternators are 60A B&C primary and 20/30A B&C backup (vacuum pump pad mounted).

I recall pictures of dual firewall mounted batteries, but after an extensive search on this site was unable to find any or they have been deleted.

I'd appreciate any pictures of the second battery, battery box, battery contactor and cross tie contactor, and battery wiring to the contactors. Any advice also appreciated.

I’m installing dual vented(to overboard) EarthX batteries lengthwise-tandem in an under-panel console on my 7A. Each has twice the CCA of the PC680, and together they weigh five pounds less than ONE PC680. Each has a contactor to the main bus. Both can be connected to the main bus using a 2-pole momentary switch for a whopping 800 CCA, but it is crucial that it be impossible to simultaneously hard connect both to the main bus to prevent discharging both before discovering an alternator failure. My master switch is on-off-on for full time operation so either but not both batteries can be hard connected to the main bus. Both have diodes for charging when not hard connected for complete symmetry(the diode for the hard-connected battery does nothing)and the momentary switch can also be used to switch main batteries in flight without shutting down any avionics. This is a good feature on long flights because diodes rob some charging voltage and it allows “Topping off” the battery that has been serving as backup during the first half of the flight.

I agree with others here that dual batteries and dual alternators equals heavy overkill. I have one very happy B&C 462H spline-driven alternator that produces a reliable and more than adequate 40+ amps - that story here: http://www.vansairforce.com/community/showthread.php?t=159331&highlight=Spline-drive+alternator

The installation you describe could be on the nose-heavy side with elevated polar mass. The price for that is some loss of nimbleness, fuel efficiency in cruise, and spin-recovery authority. Admittedly a 9 with a 320 is more tolerant of this than one with a 360.
 
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Carl Froehlich,
I sent you a PM with my email address. Look forward to hearing from you.

Thanks in advance!
 
That is a LOT of complexity and weight!

All the modern EFIS's have battery backups. Add a handheld GPS in an AirGizmo and a Dynon Pocket panel and you can navigate and aviate for five hours after a full electrical failure. (There are procedures for completing a flight without a radio, so that shouldn't be an issue but add a handheld radio, if you must.)
 
2 batts

When I purchased my RV-7 one of the first things I noticed was that the previous owner did a fantastic job putting in 2 batteries on 2 separate BUS. 2 batteries don't always need to be for IFR. The first 1000 hours of flight in my RV were all VFR with a VFR panel, but guess what, I never had to worry about a dead battery when I got in to start the plane (unless I was the idiot that left both ON). The point is this gave me the the back up that I needed when I was on cross country flights and not at home field if something happened. I always crank the plane with 1 battery, leaving the other one for back up. 99.99% the plane cranks with no problem(knock on wood), but that 1 times when it doesn't, I simply flip the switch to Batt #2 and crank the plane. Yes I charge both during flight and alternate as much as I can on which battery to start with. This keeps both exercised and both charged.
Now that I've changed my panel for IFR, the 2 batteries have given me a level of comfort that I didn't even care about before. In my situation, I have 1 alternator (like most), 2 batteries, 1 backup batteries hooked up to run G3X system only in case of hard failure, G5 with its own battery. Lots of different ways to have back up and back up for the back up, but as someone stated in a previous post, when is enough, enough? Not really sure why any single engine plane would require dual alternators, but God Bless, to each its own. We're all different and that's what is so great about this World.
 
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