You don't even start an E until the batts are already full, so you can't get any amps in at all unless you jack up the voltage. It is still all about the battery's "natural acceptance rate" (which goes up with voltage at any SOC) The batt will not accept any more amps than that, the rest goes to gassing.
If you have a large bank like mena's it will take more amps at the same voltage than a small bank will.
I don't have an ugly graph set for when "over-charging" to be able to say what amps a particular size (in AH) bank will accept at 15.5-16.5 volts. If you knew that for your size bank then you could get a charger that will do that and not waste money on getting a more powerful one.
So it is not enough to look at the specs of the charger without also looking at the size of your battery bank. This is why it is often recommended to do one battery at a time with your existing charger so the charger will have enough oomph to do it where it might not be able to raise the voltage enough on two batts at once.
