I ran accross this product but was curious to know why it says you have to use the same capacity size batteries with it.

http://www.hobbyking.com/hobbyking/s...dProduct=15237

I thought that when you do a parallel charge you only needed to make sure the cell count (s count) is the same between all batteries and you just add up the total mAh for your charge current.

I have two 3S batetries I want to charge in parallel. One is 4000mAh and the other is 5000mAh.

you need same capacity with same discharge level. otherwise you will destroy smaller capacity pack as it will be overcharged.

get second charger or a dual charger or if you want to be safe use serial charging as balance adapter is easy to make

http://www.scriptasylum.com/rc_speed/lipo.html

Packs need to be the same cell count and close to the same voltage level (discharge state)

Capacities can be different, charge current will split between them based on their needs

If you have a 4000 mah pack and a 5000mah pack you would set charge current at 9 amps (assuming a 1c charge rate)

Cheers

I have the Paraboard the EPBuddy sells and it is not limited like that. If the HK description is accurate (and I believe it is in error), they must have copied something about the wiring wrong, cause it is a copy. You're correct - you can charge same cell counts of different capacities in parallel. I routinely do it and you can find many vid clips on UTube of folks doing it. Dave Gray, owner of Progressive RC (iCharger Dealer) has one where he's charging 6 diff lipos all 3S, but all of diff capacities in parallel.

http://www.youtube.com/watch?v=NczQwVTI2bY

C Rate ideally should be the same, but there some prob here since there is no standard for setting the C rate and one companies 25C may be another companies 30C and yet anothers 20C. So even if the 'label' C ratings are the same, the actual C rates may not be. I try to match them.

Hi i need same capacity with same discharge level. otherwise you will destroy smaller capacity pack as it will be overcharged get second charger or a dual charger or if you want to be safe use serial charging as balance adapter is easy to make...

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^^^ that's not correct, you must be thinking of charging in series where the Lipos have to be same capacity, but can be diff cell counts.


Parallel charging - has to be same cell counts, ideally same C rating, similar discharge level (<0.3v is what I've seen recommended on RCG) prior to hookup, but can be diff capacities.

Series charging - has to be same capacity, ideally same C rating, but can be diff cell counts. This is much harder to do as regarding the serial balance connection arangement. If you don't get it right, you will short the lipos together. This is the reason parallel is generally preferred.

Watch the UTube clip I linked, parallel charging 6 diff lipos, same cell count, different capacities!