Discharging
 

I have two completely different chargers, both have a discharge rate of 2A. But when I try to discharge a 4200mah lipo one will only discharge at max 1.3A and the other at 0.7A. Any particular reason why?

What size are the batteries? Would think that there is a maximum discharge rate for a given battery size but as chargers are automatic "intelligent" they will discharge at a rate deemed safe.
There are chargers that put a dead short on a cell to discharge at 20a but why risk detonation (exaggeration I know but you don't do it with your mobile or lap top and they never seem to fail)

The big question is why. Why do you need to discharge a lipo?

That was my first thought. But then it occurred to me that they may need discharging to get to storage voltage

I always "storage charge" my Lipos after use....it is ,after all, the recommended procedure..!
I set my charger to discharge at 1.5 amps, but , as said above, the chargers are "intelligent" and vary the rate as needed. Same as when charging.... The discharge rate might start at 1.5 but quickly drops and decreases as the storage point approaches..... Works for me..!

I only discharge to storage voltage when I haven't raced for some reason or had a car failure early on in a race. If I've completed a 5 min race I just leave them.

The charger cant calculate the battery capacity just by connecting it up, no matter how intelligent it is.

Most charger use the discharge resistors that are connected to the balance lead to discharge a battery. The same resistors are used when balance charging. It works by charging through the main battery connector, and then discharging any cell which has a higher voltage at the same time.

The reason you probably have a lower discharge current than the max is because the charger discharges the cells in a balanced way, So if one cell has a higher internal resistance, it will be discharged at a lower current than the other, so you will never hit the max discharge limit.

Hope that makes sense.

Thanks, makes sense