Soo umm that can't be good... - RC-Monster Forums

Slowkrawl · **Soo umm that can't be good... -** 12.06.2009, 06:29 PM

Last night I was bashin the savage in the snow and all of a sudden noticed a SHARP drop in power, stopped immediatly and ran over to it to hear a "pssss" noise..I am now thinking "holy shit, it is going to light on fire" lol. I ran it to the garage cause it was about -20 and saw that the lipo had puffed... I should have known better! My assumption is that water caused the leads to short thus puffing it. Any other educated-guesses?

So while I am at it, I might as well ask a few other questions.
I am thinking I am going to try turnigy or zippy batteries, what balance taps do they use? I'm hoping I don't have to buy another adapter for the charger(I have hyperion and TP taps right now).

Also, what can a guy do to kind of waterproof a lipo? I was thinking plasti-dip but don't they need to breath a bit?

Thanks for any help guys, I am going to go mourn the loss of my lipo now lol.

-Matt

Bondonutz · 12.06.2009, 06:40 PM

I noticed even in 50 degree weather my Zippys take a while to get warmed up enough to put out normal power, could you have demanded more than they could give due to the packs temp ??

Hobby City packs have the hyperion tabs, the big plugs.

Sorry for your lose.

magman · 12.06.2009, 06:41 PM

Matt..that really suck when a battery puffs. The li-po do need to breath a bit to help release the heat build up....so I would leave them as is.

The turnigy/zippy batts. use JST/Align taps

BrianG · 12.06.2009, 06:44 PM

Water doesn't have enough of a low resistance to short a battery like that. Most likely, they couldn't deliver the required current probably because of the low temps.

Finnster · 12.06.2009, 06:45 PM

Are these SMCs?

I wonder what the min temp for running lipos is. I was running my old TrueRC packs today in the snow, but it was still 35F outside.

When you say -20, are you meaning C?

Slowkrawl · 12.06.2009, 06:50 PM

Quote:

Originally Posted by Finnster

Are these SMCs?

I wonder what the min temp for running lipos is. I was running my old TrueRC packs today in the snow, but it was still 35F outside.

When you say -20, are you meaning C?

That's what sucks about it, they are NICE thunder power lipo's. Hmm, I should have thought about the low temperature...I guess I will have to do some homework on the operating temps of lipo's. And yes, -20C. The other battery seems to be fine, cycling it right now just to make sure then it's going up for sale.

redshift · 12.06.2009, 07:11 PM

Yep, too cold. You need to look into a heating pad or similar, and also find a way to insulate the batts, I use thin packing foam.

Packs preheated are crazy punchy and shouldn't puff due to low temp because they can't really cool back off as long as they start warm. You can't keep an eye on temps with hardcases and that's why I'd never run them. You really need to know what's going on with them during a run. If you sell them do yourself a huge favor and get noncased packs next time. The cases will do nothing to insulate them, and will contribute to overheating in the warmer months, double bad news.

Slowkrawl · 12.06.2009, 07:19 PM

The thing is, the packs came out of my warm house and then ran for a while so they should have been still warm, THEN it puffed. However it was pretty cold lol. That hardcase saved my ass a couple times when it came scooting out of my slash at mach 3 haha. However you are correct, it's hard to judge temp when they are in a case. Zippy or turnigy it is!

Are align/hyperion taps the same? Just wondering because I am getting two different answers as to what HC packs have for balance taps?

phildogg · 12.06.2009, 07:23 PM

no align and hyperion are differant , you can get a cheap balance adapter from Hobbycity also.
phil

redshift · 07:34 PM

Sucks to find out that way, but it's especially of concern for the pilots. The flyers seem to have many tricks to warm them up, even if it's just sticking it in your pocket for 15-20 minutes. The preheat temps don't need to be any higher than 100F, or 38C, and should not be allowed to drop much below about 80F, or 26C.

Put em in warm and rap on them, as long as the load is consistent they'll maintain their temps. IF they aren't in a case.
Keep in mind with non-hardcased packs you may be able to jump ~1000 mah for the same pack dimensions- that's a GOOD thing...

Good luck!

suicideneil · 12.06.2009, 07:32 PM

The hobbycity packs do use the jst-xh plugs though- adaptor boards are cheap as chips though, just have a poke on the HC website at the same time as you get your new lipos.

redshift · 12.06.2009, 08:04 PM

Another general tip, do NOT charge lipos in the cold, this will actually make your charger work harder. People generally think colder is better for electronics, this is a very rare exception to that rule, lipos IR is higher the colder they are. That's also why they can't deliver the watts in extreme cold.

Slowkrawl · 12.12.2009, 12:03 PM

So, I guess we have determined how warm the packs should be for pre-heating, but how warm should they be during the run? I am just wondering how cold is TOO cold? Now that I have the esc waterproofed I want to run this thing in the snow but I guess -20 is a bit cold for the batts.

Also, I saw somewhere that hardcases really do nothing to insulate the lipos and actually hurt the insulation more than anything? I am not going to run hardcase next time just because I hate not being able to keep an eye on the batts.

redshift · 12.12.2009, 01:08 PM

Quote:

Originally Posted by redshift

The preheat temps don't need to be any higher than 100F, or 38C, and should not be allowed to drop much below about 80F, or 26C.

This was my recommendation for running temps, I guess I should have been clearer.

There is no consensus as of yet on what is too cold. That will vary brand to brand, and also vary according to C rating. It's pretty much wrap them in some sort of insulation, or take your chances.

It may be a good idea to over-gear some for cold weather running, that way the batts will likely generate more of their own heat. With so much tirespinning, the load is naturally lower, so that may also work against you.

On the flipside, if you're running in slop, then over-gearing may be bad, because loading up the wheels will then present more of a load than normal.

There's no simple set of rules for this stuff, other than personal intuition.

Just watching pack temps is your best bet, and I strongly advise against letting temps drop much below ROOM temp--- just so I can avoid the damn C vs F conversions....

Anyone else has more info, please chime in. I am NOT an authority on this stuff!

Just passing on the best info I can.

Hope maybe that helps!

Slowkrawl · 12.12.2009, 01:19 PM

I already geared up a little bit. I think if I wrap them up in a thin blanket of sorts they should be fine in -20. My other pack that didn't puff was still warm through the case 10 minutes after it happened, so hard to say how warm it was while outside.

-20 really isn't that much fun to drive in, but it's what I get to deal with for the next 3-4 months lol.