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dual battery location for RV10?

sritchie

Well Known Member
Hey folks,

I'm currently planning out my firewall and battery locations and trying to decide where to mount my dual EarthX ETX900 batteries. Couple of options:

1. try and fit both on the firewall. (I know folks will be concerned about temps here.)
2. mount both on a dual tray system like Bob Condrey's done here:

Bob_Condreys_Batteries.jpg


3. mount one on the firewall (primary) and one in the back (backup) in the stock location. I'd do the primary up front because the wire run is shorter.

Is there any reason I should do #3? I'm leaning toward #2 or #3, since it's a pain to find spots for two batteries on the firewall, assuming that #3 isn't totally unreasonable.

Would love to hear your thoughts!
 
I actually changed that after the first year to move CG forward. Put a PC-680 on the firewall and a 925 in back, worked well and several others have since done the same.

On an RV-10 you can always add some weight in the baggage area to shift CG aft, but not really anything you can do (from a loading perspective) to move it forward from empty. Ideal situation is to have the empty CG near the forward limit.
 
that's really good to know. Any reason you didn't move both batteries forward vs having one forward and one back?
 
Sam,

Send me a PM with your email and I'll provide photos of my dual PC-625 install and power distribution design.

Carl
 
Dual battery for RV10

Put them both behind the baggage compartment in the tray. I did not have enough room side-by-side so I stacked them, one above the other. They can be mounted in any orientation. I have an Oddessy 925 and a 680 with the 680 on its side on top.

The 10 really needs the weight aft. Even with 2 batteries there I carry 40 lbs of sand in the baggage compartment when there are just 2 on board.
 
The 10 really needs the weight aft. Even with 2 batteries there I carry 40 lbs of sand in the baggage compartment when there are just 2 on board.

Most 10's I've seen are already a bit tail heavy. Where's your empty cg? Do you have a heavier-than-normal prop, or ac up front?
BTW, I recommend water in plastic containers instead of sand, for ballast. If you fly solo somewhere to pick up passengers, it's easy to just pour out on the ground. And vice versa, most airports have water available.
 
Dual battery location for RV10

My empty CG is 107.82 with design range of 107.84 to 116.24.
Front seat passengers and fuel sit close to the CG making most RV10's nose heavy, not tail heavy. If you put back seat passengers and baggage the CG moves appropriately aft.

My a/c is stock with a 2-blade Hartzell.

With only front seat passengers and no ballast there is not enough trim authority to flare and land, hence the weight needed in the baggage compartment.
 
Consid

You live in Colorado so one thing I would consider is preheating the engine compartment. I live in Canada so battery in engine compartment is preferred because when you preheat engine for winter ops the batteries get some residual heat as well.

Very curious about the forward CofG on mentioned RV10. So far I've heard everything opposite which is another reason I'm going battery on firewall.
 
My empty CG is 107.82 with design range of 107.84 to 116.24.
Front seat passengers and fuel sit close to the CG making most RV10's nose heavy, not tail heavy. If you put back seat passengers and baggage the CG moves appropriately aft.

My a/c is stock with a 2-blade Hartzell.

With only front seat passengers and no ballast there is not enough trim authority to flare and land, hence the weight needed in the baggage compartment.

If you really mean that with a forward cg that there is not enough trim authority to flare and land using only the trim, you are correct. But, I doubt you need 40 lbs to bring it within the forward limit. Does it flare easier with ballast? Absolutely.
I'd say your cg is about perfect. When solo and low gas, you can afford a bit of ballast (but again, my empty cg is forward of yours, I sit forward, and only need 20 lbs). But if your really put heavy people/things in the rear seat and, especially, the baggage area, you'll be glad your empty cg is where it is. I've seen a fair number of RV-10s where it is limited by aft cg, when carrying a full load.
 
Thanks for the responses, all. I'm going with the whirlwind prop, so I think I actually might want to mount both batteries on the firewall. Each ETX900 weighs 4.9 pounds, and if I recall the difference between the whirlwind prop and the stock hartzell is ~20 pounds. Giving that up means that I'll probably want some more weight up front.

Does this seem reasonable? Would love reactions, and maybe a photo from anyone who's seen or has a great dual battery firewall setup!
 
You live in Colorado so one thing I would consider is preheating the engine compartment. I live in Canada so battery in engine compartment is preferred because when you preheat engine for winter ops the batteries get some residual heat as well.

Very curious about the forward CofG on mentioned RV10. So far I've heard everything opposite which is another reason I'm going battery on firewall.

Assuming you are using an IO-540 and Hartzell BA prop, the RV-10 needs the battery(s) mounted aft for W&B.

Check flying RV-10 W&B data and decide for yourself. Send me your email in a PM and I'll send you mine.

Carl
 
My version....

This is my version of dual batteries. Two (2) EarthX 1200's still are less weight than a single lead acid. Just modified the existing structure.

I hope this picture things works....

4
 
Assuming you are using an IO-540 and Hartzell BA prop, the RV-10 needs the battery(s) mounted aft for W&B.

Check flying RV-10 W&B data and decide for yourself. Send me your email in a PM and I'll send you mine.

Carl

Hey Carl, I'm actually using a whirlwind prop, which is about 20 pounds lighter up front. I'll PM you my email. Thanks!
 
Dual battery location for RV10

I would not put the batteries forward of the firewall, it will only make your CG worse and the temperature will accelerate its degradation.

Bob - you are correct, the 10 lands just fine without the ballast but the trim authority is insufficient to fully compensate and you need a lot of backpressure on the stick.

My sandbag weighed 40 lbs and it was convenient. My trim is still full against the stops when I land.
 
I have a lightweight whirlwind prop and dual EarthX batteries on the firewall. I'm happy with my configuration.

I don't have to, but I typically carry 2ea 25lb sand bags in back when lightly loaded. The plane just flies a little better when it's not close to the forward limit. The real advantage is I can load up the plane without the sandbags and have no CG issues.

I was able to go from one PC680 on the firewall and a single alternator to two EarthX batteries, two alternators, and 3 contactors for a net weight gain of 1lb. The 1lb was basically from the additional large cables. Note that the original battery was already small and light for a 10.

Guy
 
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I don't have to, but I typically carry 2ea 25lb sand bags in back when lightly loaded. The plane just flies a little better when it's not close to the forward limit. The real advantage is I can load up the plane without the sandbags and have no CG issues.

Guy

I do the same thing except I use a 5-gal collapsible water container. That way I can easily dump water if I fly out light but come back heavy with pax/cargo.
 
I have a lightweight whirlwind prop and dual EarthX batteries on the firewall. I'm happy with my configuration.

I don't have to, but I typically carry 2ea 25lb sand bags in back when lightly loaded. The plane just flies a little better when it's not close to the forward limit. The real advantage is I can load up the plane without the sandbags and have no CG issues.

I was able to go from one PC680 on the firewall and a single alternator to two EarthX batteries, two alternators, and 3 contactors for a net weight gain of 1lb. The 1lb was basically from the additional large cables. Note that the original battery was already small and light for a 10.

Guy

Guy, do you have a picture of your setup? I'd love to see where you placed the batteries.
 
I don't have any great photos, but here are a couple of marginal ones.

In the photo below, you can see the tops of both batteries. One lesson learned that hard way is that the bottom battery needs a radiant heat barrier to keep the case from melting. My battery functioned normally after significant heat damage to the case, but I've replaced it. Also understand that the placements might not be optimal. I rebuilt all of the systems in the plane and therefor had some additional constraints I wouldn't have had if I were starting from scratch. It originally had a single PC680 on the firewall.

2017040408315695-68A3191B-F5D9-4691-B89B-60272C641244-XL.jpg


My engine is removed at the moment for an unplanned overhaul due to cam and lifter corrosion caused by the previous owner not flying enough. The lower battery is removed due to the heat damage I mentioned above. It goes immediately inboard of the blue starter contactor.

2017053112012759-A787DF2B-34D1-41A4-B7F6-6A92588C4A63-XL.jpg


Hope this helps.

Guy
 
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Wow, looks really hot in there. I may end up going one battery forward, one back to provide some redundancy in case the heat's an issue, and to keep the second battery out of that hot spot.

Thanks again!
 
DO NOT MOUNT YOUR EARTHX BATTERY ON FIRE WALL!!!!

I am shocked to see that some are suggesting mounting the battery, ANY battery on the firewall of a RV-10. I just went down that same road and ended up losing a perfectly good ETX900 that I had placed under the copilots seat years ago. When I had a new panel all Garmin panel built by Aerotronics and installed by Synergy in Eugene, OR, Synergy suggested moving the battery from under the seat to the firewall. That way it could not only serve as the backup up power supply for the instruments but I could also use it as an alternate way to start the aircraft. They had done that on MANY of the two seat versions of the Van's aircraft. We did move it to the firewall and I flew the aircraft back to California in late July. In August I flew to Colorado and to Arizona and it was very hot. Finally in about October when I attempted to use the backup battery on the firewall, it was DEAD! When I tried to remove it from the battery box it was difficult. Turns out the reason it was difficult was because the case was distorted. I ended up sending the battery back to the Lab at EarthX to find out what had happened. First of all, they said the temps in the compartment exceeded 140 degrees because that is the temp were the case starts to change shape. Secondly, the internal temp of the battery should never get above 125 degrees, obviously this happened. I wrote to Vans and to EarthX asking about the temps in the RV-10 engine compartment but no one knew what they were. Vans simply said "we know its too hot, put the battery in the back (also helps with CG). I decided to do some testing myself and found that the temps were all OK as long as the big fan on the front of the airplane is turning BUT when you shut it off, bad things start to happen. After shut down, if you open the oil filler door on the top of the engine compartment, the temps go to a max of 153 degrees before starting to cool down. That is obviously way past the 125 max that EarthX has said is the internal cell temp and also exceeds the 140 where the battery case changes shape. Well it gets WORSE, much worse. If you do NOT open the oil filler door, the peak temp goes to 165 degrees, four minutes after shut down. I recorded all of these temps and sent them to both Vans and EarthX. The VP at Vans called me and thanked me for the information as they really didn't know. I would post this test document data but it is in word format and I am not sure how to do that. If someone can tell me how to post it here I will. DO NOT PUT A EARTHX BATTERY IN THE ENGINE COMPARTMENT, YOU WILL BE OUT $499 JUST LIKE I WAS......
 
DJP, it looks like the battery box posted by EarthX one post up solves your issue. At 185 deg convection heat (i.e. after shut down) it takes 90 minutes of continuous heat at this temperature to raise the internal temperature to 140 deg.
 
Clarification of data points

There might have been some typo?s on the degree temperatures listed that DJP posted so I wanted to clarify some data points.

The findings on DJP battery was the temperature was above 200 deg F, because it is at this temperature the ABS plastic case will begin to deform (not the 140 deg F listed).

The max operating temperature for the cells is 140 deg F or less (not the 125 deg listed). The max storage temperature for the cells is 158 deg F. When the temperature is above this, you will start to prematurely age the cells and cause damage. (Note: the PC680 lists 113 def F as the max operating temperature). These parameters are listed in the manual on the battery specification page.

What can be learned here is every battery, no matter what brand or chemistry, list the max operating and storage temperatures and if you exceed them, you will have premature battery issues. If you are moving the location of the battery from where the aircraft manufacturer designed it to be, there might be a reason why it wasn?t located there in the first place and testing the temperature, is an excellent idea. It is a very simple test, which DJP looks like he will list how he did it, to perform and would be a good idea if you do have your battery installed fire wall forward, again no matter what the chemistry.
 
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Sorry my mistake about the numbers

Kathy is correct, it is 200 degree's for the battery frame and 140 for the cells. Having said that, the tests that I ran shows that those numbers ARE reached easily on any given day and at some point I exceeded 200 because the battery was distorted. The insulated battery box that EarthX sells is supposed to mitigate battery damage BUT after paying twice for a $499 battery I decided to move mine to the tail where the regular battery resides. You remove the battery from a huge heat source and get CG help in the process. My test results are posted below:

Test Equipment used +/- 1.8 Degrees accuracy
Lycoming IO-540 Engine Compartment Heat Test Results
Outside air temperature at engine start 59 degrees F.

Idle 91 F
Taxi 107 F
Run up 101 F
Take Off 112 F
Climb 119 F
Cruise 115 F OAT 69F @ 4,500 Feet, MP 21/RPM 2300
Descent 110 F
Taxi 108 F

Engine shut down with oil filler door wide open:

Max temp 153 F. Temps increased for 8-10 minutes after shutdown @ 15 minutes temps started dropping.

Same Test with Outside Air Temp 81F

Engine shut down with oil filler door CLOSED:

Shut down temp 125 F
In two minutes 155 F
Peak Temp 165 F Four minutes after shutdown
Within 4 minutes of peak, temps started dropping.
11 minutes after peak, temp dropped to 155 F
 
Kathy, I just received the insulated battery box and plan to mount it firewall forward on my 10. What about creating a lid for the top of the box that would still allow a blast tube to be on it (with an exit, of course)? I can see how the insulation can help prevent heat soak but with the top of the box still open, the lingering heat of the compartment can still get to the exposed surface of the battery. I think if the top was enclosed you'd have better protection from the residual heat after shut down.
 
Kathy, I just received the insulated battery box and plan to mount it firewall forward on my 10. What about creating a lid for the top of the box that would still allow a blast tube to be on it (with an exit, of course)? I can see how the insulation can help prevent heat soak but with the top of the box still open, the lingering heat of the compartment can still get to the exposed surface of the battery. I think if the top was enclosed you'd have better protection from the residual heat after shut down.

Tim,

Just curious, why do you think all the advice from builders about not mounting batteries on the firewall of an RV-10 is wrong?

Carl
 
Thermal battery box design

Kathy, I just received the insulated battery box and plan to mount it firewall forward on my 10. What about creating a lid for the top of the box that would still allow a blast tube to be on it (with an exit, of course)? I can see how the insulation can help prevent heat soak but with the top of the box still open, the lingering heat of the compartment can still get to the exposed surface of the battery. I think if the top was enclosed you'd have better protection from the residual heat after shut down.

Hi Tim, that is a great question. It was an engineering decision to not have a top to the box as it significantly increased the costs and it did very little to increase the protection of the cells which are located where the greatest protection and insulation is located.
 
Hi Tim, that is a great question. It was an engineering decision to not have a top to the box as it significantly increased the costs and it did very little to increase the protection of the cells which are located where the greatest protection and insulation is located.

Good information, thank you.
 
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