MethTek "Ammo Box" Battery Build 20S2P

S

Stochastic

100 mW
Joined
Jun 5, 2011
Messages
46
Location
Livermore, CA
This is another battery build I have been working on at MethTek. It's a battery pack made in an air tight and water proof ammo can! I built it with 10 4S Hardpacks in a 20S2P configuration. Everything will be secured inside as to not rattle around or rub against each other. This pack will be built for abuse and even wet conditions with HVC and LVC protection!!! Who could ask for a more rugged and safe solution? :shock:
AmmoBox4.jpg

It's almost done... all I have left to do is rout the main power out either through a grommet or some type of Bulk Head Connector (haven't decided yet) and also hook up one of our HVC Relay boards to the pack. :mrgreen:
View attachment 1

I left a 4S tap from each of the HVC/LVC boards inside of the pack so that it can be balanced with the "Battery Medics" or a regular 4S balance charger such as the 420 charger from HobbyKing.

-Matthew

AmmoBox1.jpg
AmmoBox2.jpg
 
Put some vent holes in it somewhere. Mabye on the bottom, or if on the ends a louver could be added to keep water out.

Don't want it too sealed. On my storage boxes, I just drilled holes, then taped over them. the tape on the outside will blow out if the batts make gas.
 
dogman said:
Put some vent holes in it somewhere. Mabye on the bottom, or if on the ends a louver could be added to keep water out.

Don't want it too sealed. On my storage boxes, I just drilled holes, then taped over them. the tape on the outside will blow out if the batts make gas.
Click to expand...

+1, if those things go up, the ammo can, can become a pipe bomb. Otherwise the thing is gorgeous!

Just give it somplace to vent. The lid may not be perfectly airtight anyway, but a little extra something is some piece of mind.
 
You guys are doing great work.. Love seeing the more friendly products..

Heck this is the best pic to date I have seen of these new boards in action.

Keep it up.
 
Look sweet, I have hardcase 4S LiPo and PLEASSSSSSE make 4s LVC boards. I need it and making 16s4p (20Ah) pack. :lol:

All I know Patrick (Methods) offers 5s and 6s lvc boards as what he told me. :wink:
 
grindz145 said:
dogman said:
Put some vent holes in it somewhere. Mabye on the bottom, or if on the ends a louver could be added to keep water out.

Don't want it too sealed. On my storage boxes, I just drilled holes, then taped over them. the tape on the outside will blow out if the batts make gas.
Click to expand...

+1, if those things go up, the ammo can, can become a pipe bomb. Otherwise the thing is gorgeous!

Just give it somplace to vent. The lid may not be perfectly airtight anyway, but a little extra something is some piece of mind.
Click to expand...

I'll put some type of ventilation on the box but I also want to maintain the integrity of what the ammo can is, waterproof. Or maybe I want a LiPo bomb sitting between my legs. :shock:
 
One real good way to seal a hole in a metal object, is heating and cooling duct tape. That's the sticky back aluminum foil stuff.

Very good stick compared to most tape. I used to use it regularly to do a temporary repair on a windsurf board, then fix it right when I got back home from vacation. No problem sticking underwater. But if the box got pressurized, the thin aluminum would pop before the box could distort. Nowdays there is good duct tape again, so gorilla tape would work just as good I bet.

The aluminum tape is very paintable too.

Another option would be to simply change the way the lid is held down. Remove the bail, and secure the lid with someting less sturdy. Tape, zip tie, something that would break in time if the lid needed to be forced up.

Same foil tape is ideal for covering holes in motor covers, btw. So you can run sealed, but open up to let water out once a month or so. It's high temp tape for hot ductwork.
 
I was looking at ammo cans too. One possible solution to the vent issue would be if the latching mechanism was spring loaded so that any pressure inside could slightly open the cover to vent. Drilling a big hole and covering with tape is not a bad idea either.

How much does the empty ammo can weigh?
 
I was thinking of using some rubber grommet type plugs which could provide water protection and easily blow out in the event of an epic failure. I could even put some tape over it... :shock:

Something similar to the ones in this kit: http://www.amazon.com/125pc-Rubber-Grommet-Plug-Assortment/dp/B00552Q1P6/ref=sr_1_2?ie=UTF8&qid=1329329816&sr=8-2
 
Grommet plugs would work fine. They'll blow out long before the can blows, well, at least they will if your thermal event is fairly slow at the beginning.

I watched an open top coffee can go off once, but it was full of exlploding firecrackers. You'd think the open top would allow the gas to escape fast enough, but not when the can was full of black cats.

Hopefully, in an event, you'd notice a sound when the tape or grommets pop. Then have time to get clear. At some point, the open top might not be enough if you opened the lid.

The more I think about it, removing the bail on the lid might be best, then secure the top with something with break away ability. That can will be too hot to touch to open the top in an event.
 
chroot said:
Look sweet, I have hardcase 4S LiPo and PLEASSSSSSE make 4s LVC boards. I need it and making 16s4p (20Ah) pack. :lol:

All I know Patrick (Methods) offers 5s and 6s lvc boards as what he told me. :wink:
Click to expand...

I might be able to make some up for you if we get some 4S headers in, we're out of them at the moment. I had to pick through a bunch of crap just to find enough to populate 3 on each of these boards.
 
i don't think it's wise to let pressure build up in the box. then if the pressure is high enough i will/may push out the grommets. but if the raise of pressure is too high and too fast the thing will blow off as one big bomb. so as soon as there is a slight raise of pressure it should be able to escape.
just my 2c
 
Yes, like the open top coffe can with firecrackers, the pressure could build even if the top flipped open. Removing the bail from the latch makes sense to me, then something easily cut will at least pop the lid before it really pressures up.

Testing with compressed air might help tune the design.
 
I think I should pressure test it with some actual failing LiPo batteries.... :mrgreen:

I got a few 1" and 3/4" rubber plugs which I think will do the trick. I'd prefer to keep the integrity of the ammo box and just drill a few holes on the bottom and plug them with the rubber plugs. 8)
 
I angle-ground out some cuts in the top edge of the can on mine:
http://www.endless-sphere.com/forums/viewtopic.php?p=536242#p536242
for the cables and for venting. With the cuts under the "overhang" of the lid, they'll still protect against direct water/debris ingress, but still allow any kind of gas exchange that's needed. At least, that's the idea. ;)

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file.php


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I'd like to see what happens to one of those cans if you partially fill it with hydrogen and spark it (video for sure). I think that would be the worst thing that could happen to it.
 
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