Unhappy with Lipo Performance

[skellyo]

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?

[MarkF]

Packs will get hot if you run them down all the way.

Mark

[tsenecal]

although I don't own any polyrc lipos, i have seen batteries for r/c cars listed at their max rating, not their continuos rating.

you can get a temp probe for your eagletree, and monitor the temp of the battery over the full length of the run, and get a better idea of what the battery is actually doing.

[JimClark]

There are just too many unknowns on this to just blame the batteries. CG prop size friction int he drive run time

JIm

[BakedMopar]

My zippys gets an average of 15 degrees hotter than my turnigys. Same size 5000 40-50c.

[skellyo]

There are just too many unknowns on this to just blame the batteries. CG prop size friction int he drive run time

JIm

I'm not unhappy with the way the boat performs. I'm unhappy with how hot the lipos are getting relative to the current being drawn versus their C rating.

[BHChieftain]

I'm not unhappy with the way the boat performs. I'm unhappy with how hot the lipos are getting relative to the current being drawn versus their C rating.

As MarkF said, if you run the pack empty it will get really hot. How long are your runs? What happens to the temps on a 1/2 or 3/4 run?

-Chief

[m4a1usr]

Capacity typically gets better with lipo useage. In other words they are not at their best when the packs are new. I know with my packs I dont see the best performance out of them until I have 8 to 10 charges into them. I know it sounds weird but it seems to hold true for mine. Doesnt matter the brand.

So if your packs are brandy new you might consider giving them a little more time to gain capacity or the chemistry to mature. Just my 2 cents.


John

[JimClark]

I don't have an eagletree and not sure I am reading the graphs correctly. Did you run it fir 11:59? What is the difference between the red and the green graphs?

I assume these were Venom packs?

[skellyo]

I don't have an eagletree and not sure I am reading the graphs correctly. Did you run it fir 11:59? What is the difference between the red and the green graphs?

I assume these were Venom packs?

The red is the current draw from the battery pack. The green is the voltage of the battery pack. The scale at the bottom that shows from 170-280 is time in seconds. I zoomed in on the graph from when it went in the water to when I pulled it out of the water, so it was around 2 minutes of run time just to get some data.

The packs in question are Poly RC which are built with Enerland cells. It's a 25C continuous pack, 50C burst.

[sailr]

25C 2200mAh pack should be able to deliver 55A continuously. According to your graph, the MAX amps you reached during your run was 34.66A with an average of 16.07A. The battery should just barely be lukewarm if not cold! Somethin wrong with the pack like a bad cell. Did you check the voltage of each individual cell after running? A seriously out of balance pack can get really hot also.

[skellyo]

25C 2200mAh pack should be able to deliver 55A continuously. According to your graph, the MAX amps you reached during your run was 34.66A with an average of 16.07A. The battery should just barely be lukewarm if not cold! Somethin wrong with the pack like a bad cell. Did you check the voltage of each individual cell after running? A seriously out of balance pack can get really hot also.

Yes, I put it on my Hyperion Duo and the cells were all within 10mv of one another. And I agree that the pack shouldn't be hot at all. I'll be trying out some different packs over the next several weeks and will report back how they perform in comparison.

[JimClark]

Ok I agree they should not be that hot. I have never had any problems with PolyRC maybe you got a bad one. Does it do the same on all three packs? i would be calling the place you bought them from.

[JohnZ]

One of the cells could have a high resistance. My FMA Celpro 10 has the capability of checking the resistance of each cell while charging. very interesting to see the results of even big name brand packs after a season of flying/racing/ etc.

[sailr]

Exactly. I have some older packs that balance out great. Charge up great, but they have no endurance whatsoever and will get hot. They will bench test great every time. Go figure.