Battery box construction?

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SteveR

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Jan 11, 2005
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I'm going to build a battery box for my plane. I only need to power my radio and GPS, so I don't need a big battery. I found a sealed 12v 8AH battery that should work great. I want to put it in a battery box even though it is sealed, just in case. I originally intended to build an aluminum box, but I'm not sure how to seal the seams. I don't have the ability to weld aluminum.

Would fiberglass resist battery acid? It shouldn't be too hard to build, and would be lighter than aluminum.

Also, is it common to put baking soda or some other base in the bottom of a battery box, to help neutralize the acid in the event of a leak?
 
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Craig

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Jupiter, Florida
Battery box

Steve -
Generally, with a sealed battery such as you describe, the box is there to protect and house the battery. As they are sealed, they need no vent or acid retainer structure - but they do need to be protected from accidental knocks, and of course you need something to hold it so it doesn't wander around the floor.
I use a simple, riveted aluminum box for my Concorde battery - it has no vents, using something called Helium recombining to return the outgas to the liquid. I did plan on, and do use, a liner made from the poly sign material that you see along roadsides. Some piano hinge and a couple of adjustable latches, and a simple mount make the thing work. I even mounted the battery solenoid on the side, and a 12 V outlet for the GPS on top of it.
Good luck with your Piet - they are fun airplanes!
 

SteveR

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Norman, OK
Thanks for the tips Craig.

I'm considering making a riveted aluminum box, and sealing the seems with JB Weld. I don't know if it is inert enough to resist battery acid, but I hope it would at least stop leaks until I found it. I know a sealed battery is not likely to leak, but I can't stand thinking about the damage it might do, that could easily be prevented with a box that is sealed on the bottom.

Or maybe I can find a shop that can weld aluminum? Hmmm....
 

Rhino

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Call me simplistic, but I'd just buy one of the plastic battery boxes they make for boats. They're cheap, light and do the job.
 

SteveR

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I'd like to buy a plastic one, but the battery I'm using is REALLY small. Roughly 2"x3"x6". Enough to power my radio & GPS for 10-15 flights. Maybe I should just try to find a similar sized plastic box? What are those boat battery boxes made of, HDPE?
 

Rhino

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Most are polypropylene I think. I personally wouldn't worry about extra size unless space is at a premium, which it may very well be in your case. My concern would be more with the weight, and a large polypropylene box would still be lighter than a small metal box. I can certainly understand though if your circumstances absolutely require the smaller size.

Look at the U-1 Small Battery Box on this page. Would that work?

http://www.midstatebattery.com/boxes.htm
 
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SteveR

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Norman, OK
I need something that my battery will just barely fit in. Where it is going, I'm not going to have any extra space at all.
 

Rhino

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Then you would likely need to fabricate one or simply do without one entirely. As Craig noted earlier, sealed batteries don't normally have boxes because they don't really leak or leach. If you really do fear that such an unlikely leak may occur, you could go with something similar to automotive installations. Just build a battery tray to mount it on and place a battery pad underneath it to soak up any leaks that may occur, though I doubt they ever will. Many vehicles have battery pads underneath the battery, and the parts shop at a local car dealership could probably help with that. I believe my F-250 pickup has a pad underneath the battery, though I suspect it's more for insulation because my battery is also sealed and will likely never leak. As far as materials are concerned, I would go ahead with plastic or aluminum, though I would consider aluminum sacrificial. Should one of those unlikely leaks ever occur on an aluminum tray, build a new tray and get a new pad once the leak has been dealt with. As was also noted earlier, battery acid would corrode the aluminum and you wouldn't want to take any chances. I'd make the tray and pad a regular inspection item for that reason. Normally I probably wouldn't use aluminum for a battery mount, but since it's a sealed battery the chances of it ever being a problem are severely minimal. Building a simple aluminum tray would be a simpler solution than any other I've heard proposed here, and it would still be inexpensive even if you had to replace it once or twice due to those aforementioned unlikely leaks. Of course, this is all just my personal opinion.

Just as an aside, if your weight and balance will allow it, you might also consider remotely mounting your battery elsewehere that might allow the use of a larger box.
 
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Midniteoyl

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Indiana
Originally posted by SteveR
I'd like to buy a plastic one, but the battery I'm using is REALLY small. Roughly 2"x3"x6". Enough to power my radio & GPS for 10-15 flights. Maybe I should just try to find a similar sized plastic box? What are those boat battery boxes made of, HDPE?
Put 2 batts in a single box :p:
 

Midniteoyl

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Originally posted by Rhino
Most are polypropylene I think. I personally wouldn't worry about extra size unless space is at a premium, which it may very well be in your case. My concern would be more with the weight, and a large polypropylene box would still be lighter than a small metal box. I can certainly understand though if your circumstances absolutely require the smaller size.

Look at the U-1 Small Battery Box on this page. Would that work?

http://www.midstatebattery.com/boxes.htm
Dimensions: (outside) 8-1/4"L x 5-1/2"W x 6"H
(inside) 11" x 7-1/2"W x 8-3/4"H
Hmm.. the inside is bigger than the outside :whistle:
 

Falco Rob

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Perth, Western Australia
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Originally posted by SteveR
I'd like to buy a plastic one, but the battery I'm using is REALLY small. Roughly 2"x3"x6". Enough to power my radio & GPS for 10-15 flights. Maybe I should just try to find a similar sized plastic box? What are those boat battery boxes made of, HDPE?
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Steve,

Try your neighbourhood store for a suitably sized tupperware container.

Don't laugh ! Those things come in a zillion sizes and are more than adequate for your purposes provided you strap the battery securely to the airframe, not the container.

The downside is you'll never hear the end of it if you ever tell anyone what it really is.

I'm speaking from experience here - I made my nylon rudder pedal bearings from a breadboard and that's provided hours of merriment for the local hangar rats.

Cheers,

Rob
 

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