Lipo-impact damage?

[Gustav]

I'm wondering how robust lipos are in an offroad environment.i would leave them somewhere after a run where i can see if they swell,and they'd be stored in a safety case.Also, i'll use FMA impad to protect them from impacts.i was wondering what the risk of a short is due to the inevitable rough and tumble,have any of you guys ever had a problem or is this worrying about nothing?

i think when the plane guys have a problem seems to be when they piledrive into the groung from 100ft or so but i reckon we must pull some high Gs in a bad tumble or landing big jumps.

i'm getting them anyway,i'm just wondering how hard they are to damage.

Thanks for your comments.

[Papa]

Let me start by saying I have Zero first hand experience with the Lipo packs. I feel like impact damage is a reasonable concern. The only counsel that I have received is to utilize Associated battery cups for mounting in a Gmaxx chassis. I have heard stories of The normal Velcro straps creating impressions on ends of lipo packs when tightened to much. The IMPAD sounds like a good idea. I have seen them used as endcaps, and as pouches for lipo packs. I am worried about how the padding would effect the temperature of the packs. Additionaly I have visions of all the little projectiles thrown up at the packs, from the tires, poking holes in the packs.I can not help but to think some hack may t - bone my rig and slaughter these expensive packs. I guess Its just hold on and pray.

Basically I have 4 options

1 Impad and Gmaxx straps.
2 Associated battery cups.
3 Zip ties and a prayer
4 Velcro on packs and a Gmaxx CF rigid battery strap

I am undecide as to what to do?

[Papa]

Impad used as endcaps

[Gustav]

Thanks Papa,i'm going to use the impad as end caps and build some sort of protection around to prevent a hit from projectiles from the tires.Maybe make make some alu battery cups wide enough for the impad.

i've never held a lipo yet so i don't know how squishy they are,if they're quite soft i might use an extra piece of impad between the end caps for the middle of the pack to sit on to prevent it sagging.(the impad is 7mm thick)

i think i read that the packs have space between the cells for air to circulate so the impad end caps may be ok,other wise i might just line the area they sit in with it.

[MetalMan]

Lipos aren't soft. If they are, then that would indicate that a cell(s) has puffed up and gone back to its normal size. If this has happened, then the Lipo has been damaged and shouldn't be used.
Lipos might be slightly soft, but for the most part, they are hard. I suppose if you pushed hard enough they might dent, but why would you do that? And over time a Lipo pack is likely to get small dents. These will not harm the cell as long as long as they have not caused the inner part of the cell to be exposed to the air.

[squeeforever]

so how hard is it to damage them? is a pad like the impad neccessary?

[MetalMan]

You don't need foam THAT thick. Under my Lipos I like to use a 1/8" thick firm pad (the type that you sometimes get in packaging). I also like to have a 1/8" thick piece of polycarbonate under the Lipo pack if I am using 2 cells length-wise. This makes the pack more together.

[Gustav]

So are there a few layers surrounding the inner part of the cell? I read that them not being metal cased was intended to make them safer, i suppose so they can swell before venting,although now some cylindrical cells allow venting.

yes the impad is rather thick,more desinged with planes in mind i think,i'm going to try it since it's specifically designed to absorb impact,maybe good for ESCs too.I'd like to try to cut it so it's not so thick,7mm is alot.

[MetalMan]

Correct, there is only the outer layer. The main reason that they aren't in a round format is because of a possible fire. Standard Lipos are allowed to expand from the internal gases that can be created (puffing). If this were to happen to an unvented round cell, you would basically have a sharpenal grenade... Some (all?) NiMh cells allow the cell to vent in case of gas build-up. This would be rather unpractical (IMO) in the case of Lipos because if the vent failed, then there would likely be an explosion.

There are other Lithium cells that are contained in a round cell (not LiPo or LiIon). These are LiFePO4 (Lithium Iron Phosphate). They are like a stepping stone between Lipo and NiMh. If you are interested, I can start a new thread on them with more info.

[Gustav]

Yes a thread on LiPhos would be cool if you have more info.I'd never heard of them 'till the other day.we were discussing them in 'what do i need' in pre-sales questions(it was a little off topic).
we were looking at the Saphion cells but seems like they have a way to go to be viable for our applications in the capacity and amp handling stakes.Serum mentioned that Sony have a 20C continuous 2200 mah cell.That's 44 amps continuous isn't it?

[MetalMan]

Yes, these are the new Saphion "Power Cells". I will work on the new thread.

I haven't heard of any Sony 2200mah 20C cells. And at 20C, that would be 44amps.

[Papa]

What about battery temps when using a padding like IMPAD?

[MetalMan]

It wouldn't be a bad idea to check on the temps. You could expect that the temps enclosed by the foam will be about 10 degrees (F) higher than any uncovered part of the pack. In other words, the uncovered part of a pack shouldn't exceed 125 degrees.