25C Poly RC Lipo getting hot at 16C peaks
 

I posted this on a boat forum regarding some Poly RC packs I recently ran in my boat.

I picked up a Mini Cat Racing Velocity Mono several weeks ago and 3 - 3S 25C 2200mAh Poly RC packs for it. I expected these packs to run very well in this boat. However, I was very disappointed with how hot these packs were after running. One run a pack hit 148F! To be sure I didn't have an unexpectedly high current draw, I picked up an Eagle Tree datalogger and ran it for a few minutes this morning to get some data. It backs up my assertions that the pack just isn't that great. However, it does hold voltage at ~3.6V/cell at the highest current peak on my plot, but that's at only ~16C from a 25C continuous pack.

Has anyone else had issues like this with a pack where it's used well below continuous C rating, but still gets way too hot?

http://skellyo.com/ET/Vmono_ET_052910.jpg

could the label on the pack overstate its capability? Its the old story pay peanuts get monkeys.

Poly rc is hardly known to be a low end pack so I am rather surprised. I would be curious to know which cells they are using in these. I have never had this issue from a higher quality pack like this. In fact maxamps were the only ones I have ever had issues like this with.

Are they in an enclosed space, where excessive heat just builds? How much capacity was drained to reach that temp? Also in comparison to land vehicles, isnt the average, quite a bit higher in relationship to it's max amp draw?

It is an enclosed space, but they are the hottest thing in the boat. The motor and esc are a good 30F lower in temp than the lipo, so the ambient air around them isn't causing the greater increase IMO. I think the best thing to try now is different lipos. The boat runs great, I just totally wasn't expecting hot batts when they're not being discharged at even close to their C rating.

try some nice turnigy 40c packs. they are dirt cheap and i would be very surprised if they broke 100F.

or, you could get a hyperion 35c or 45c pack.

How old are they? The cells may just be worn out, and can't put out the amps they used to.

*edit* Duh...answered my own question. Sorry.... :oops:

So they aren't old to you, maybe they were on the shelf a bit too long?

PolyRC has a lot of grades of cells as do most companies

It may be an older gen pack pack - which ages them and increases internal resistance

Also cell heat isnt bad as long as they come about in the 50 celcius range - preheating to 45+celcius reduces the internal reistance and delivers a definite boost to voltage under load.

Finally continuous/peak ratings are arbitrary. nothing runs continuous amps and only LMR gliders nd drag racing run real peak amp loads.

Altho I use Thunder Power in all my marine racing I use the continuous rating as a peak rating. I only hit it when i enter a turn at full speed. i run the same course every time and take out 2300-2600mah from a 5000mah pack in 60-80 seconds the packs ciome ina t 45-50 degrees celcius