Parallel packs mha difference ?

[andym]

Hi guys and galls a question for you. I have set up my DF33 to see just how fast she can go. Have a 1527 1d installed with a hydra 240. As this is for extreme RC fun and NOT racing ( 1p rule) I am running 4s 2p in parallel. My question is can I run a 5000mah 25c PQ and a 6000mah PQ pack in parallel? All my packs are 25c 4s PQ packs. I have run high 50's with my trusty 1515 1y on 1p but this beast of a motor (1527 1d) is a amp monster!!! and I hope to get in the high 60's....

[Ub Hauled]

I would not do it just for the safety of the smaller pack itself...
adding the packs should not be a problem, the problem would be once
they get closer to being empty... ideally one would use same mAh packs.

[andym]

Thanks UB I could not remember if it was OK or not, I know that you can run diiferent packs of the same c rating ie 4s1p and 2s1p in series to get 6s but was unsure about parallel. Have enough packs of the same cell count, mha and c rating of similar age that it will not be a problem but for wieght bias was thinking of a 5000mah in the centre and a 4350 on the left side. Same manufacturer and c rating both 4s just different mah. Will not do this now unless there is solid proof that it can be done safely.

[Ub Hauled]

they probably have a different internal resistance (different amp packs), so if possible
you really don't wanna do it. I have run different voltage packs with same amps and C rate
and even then the 2 pack got warmer then the two 4s packs I had running in series along with it...
don't ask me why but it so happened. IMO it's best to run identical packs together...

[andym]

Ok now for the amp profesors out there what do you think this will pull with a prop in the 53mm+ size? This motor has the torque to spin up a large prop. Have only run a m447 ans x446 so far. Is faster than the 1515 1.5y with thw m447 by approx 5mph but does not run the 1527 1d in its efficency range and I feel needs to be loaded up some more.

[mtgoat]

I was astonished to see two guys at the pond just yesterday running unequal packs in parallel. One said he does it all the time but is careful to limit his runtimes. I wouldn't try it.

[kevinlew211]

its ok to run unequal mah pack in parallel, but NOT continues, and like he said: you have to becarefull with your running time because the less mah pack will be empty 1st, so base on it to limit your runnin time.

[Flying Scotsman]

I may have got this wrong but would the pack with more voltage not try to charge the pack with less voltage? or is that a series problem?
Douggie

[Darin Jordan]

I may have got this wrong but would the pack with more voltage not try to charge the pack with less voltage?

Douggie

You are somewhat correct...

The packs actually would likely start out at the same voltage... However, even with Lipos, the discharge curve of the lower mah pack would drop faster than that of the larger pack. The connection, however, would attempt to balance out the voltage, pulling V from the larger pack, simply because it hasn't reach the equivalent lower level of it's discharge curve.

I don't see a big problem with doing this as long as it is observed that you only run to the capacity of the LOWER MAH pack... It'll reach it's 80% discharged point faster than the larger pack...

Personally, I wouldn't do it, but that doesn't mean it can't be safely done. You just have to accept the risk that you may damage the smaller pack eventually if you run too long.


By the way... I LOVE your new avatar, Mr. Scotsman... "Ello... Names BRUCE!!!"

[Flying Scotsman]

Thanks, Darin

Bruce was one of my favourite characters and is A typical for my personality

Bruce/Douggie