You are limited to the power that is available, for example if the charger is rated for 1000W but your supply can only provide 750W then you will only get around 600W of output due to inefficiencies which are variables due to heat, wire length, connector quality etc...

Too many variables to give hard set numbers, but it's best to use a supply that's over rated by at least 25% to ensure you get max possible potential from your charger.


When you say 1C, how many amps are configured? How many cells?

If the battery has aged, then you want to take some IR readings, more info here with my thoughts on IR:
https://www.rcgroups.com/forums/show...0#post43510433

If your IR is not matched then you may be suffering with severe balance current limitations