My 15c TP lipo gets hot but not my 20c hextronic after flght

[pcar993]

In 6 minutes of mainly hovering and some FF, both my thunder power 15c 2100 lipo gets pretty hot. I would say 138deg. On the other hand both my new 20c hextronic lipos get warm. What am i doing wrong? I checked my belt tension and all the bearings and they seem to spin free. It cant be from that because my hextronics get warm while my TP gets hot. Anyone care to explain what im doing wrong? Do TP naturally run hot? I read somwhere that it should never pass 140deg. So im a little worried. This is on my stock trex 450se. Both are 3s lipos.

Thanks.

[kgfly]

Do you mean why do the 15c get hot when the 20c only get warm ? Simple answer is that the 15c is more stressed at the same load than the 20c. The internal resistance of a 15c is approx 33% higher so for the same load current it will generate 33% more heat. 138F is too hot. Every degree above 140 wipes about 10 to 15 cycles off the pack lifetime. As the pack wears, internal resistance goes up, aggravating the problem.

How many cycles do you have on the TP 15c packs ?
Have the TP packs ever been over discharged (more than 80%) ?
Have the TP packs ever been bent, dented or damaged in a crash ?

All the above can increase the internal resistance/decrease the effective C rating and hence lead to hotter batteries.

What motor/pinion ?
What charger/balancer ?
How many mAh goes back into them when you recharge ?
How many mAh goes back into the HXT packs when you recharge after a similar 5min flight ?

[Skiddz]

You runnin' the 430L or 430XL motor? If the latter, 15C batts are gonna have the guts sucked out of 'em. I can't run my 15C TP2100s on my 450V2 'cuz the XL motor draws too much power.

Something is really pulling juice from those TP packs. Your 20C packs don't have to work so hard to provide the wanted power so they don't heat up as much.

I run the 430L on my 450SE (v1.5) and 15C TP2100 packs and they barely get warm to the touch. How much pitch are you running? What headspeed? Have you checked the solder joints on the batteries to make sure they're not cold (dull grey) or cracked?

[pcar993]

Do you mean why do the 15c get hot when the 20c only get warm ? Simple answer is that the 15c is more stressed at the same load than the 20c. The internal resistance of a 15c is approx 33% higher so for the same load current it will generate 33% more heat. 138F is too hot. Every degree above 140 wipes about 10 to 15 cycles off the pack lifetime. As the pack wears, internal resistance goes up, aggravating the problem.

How many cycles do you have on the TP 15c packs ?
Have the TP packs ever been over discharged (more than 80%) ?
Have the TP packs ever been bent, dented or damaged in a crash ?

All the above can increase the internal resistance/decrease the effective C rating and hence lead to hotter batteries.

What motor/pinion ?
What charger/balancer ?
How many mAh goes back into them when you recharge ?
How many mAh goes back into the HXT packs when you recharge after a similar 5min flight ?

I have the 450SE v1.5 stock speed control and motor. Blade length 335 wood with the longer 220mm flybar and weights next to the padle. I dont know what my pinion is but whatever stock is. I havent checked headspeed yet. My charger doesnt tell me how much mah i put back.