Using two chargers

[Ip485]

A previous thread didnt quite clarrify this for me, so the question is with two intelligent charges (of different makes and outputs) can you use both to charge at the same time?

Most people seem to think you definitely can until the battery approaches being fully charged - although I have read the odd comment that you will damage one or both of the chargers.

The position seems less clear approaching full charge. Probably there are more comments of a fate worse than death with the chargers constantly cycling as each trips to and from float, and various other grim problems, to those that say its not a problem - simply both chargers will eventually settle into providing a float current and no harm will be done.

Is there a way of calculating the maximium worth while charge to minimise the charge time? Presumably even during the intial stages there is a maximium amount of amps theoretically a bank will take - in my case about 650 Amps of AMGs. Presumably you should add to this figure whatever amps are being drawn from the batteries while they are being charged? Is this published by the manufacturers or is there some other way to establish this? Presumably with a big enough charger (or two as above) if less amps are being supplied than the total rated output this lower figure is the maximium amps the battereis can absorb?

[smac999]

Fine. Ideally both set to same bulk / float voltages. If not. Worse case one just stops charging before the other does. Not a big deal once the battery is out of bulk anyways.

With a 650a agm bank you'd want to be in the 150a -200a charger range. Assuming you have the gen /shore to run it. That is pushing it for 30a service. Can't run anything else.

[a64pilot]

Yes two chargers or three or even four will play together just fine.
First, as long as voltage is set correctly, you cannot overcharge or harm a bank no matter how big the charger is. The bank will only accept what it’s capable of. It’s when voltages are set too high that banks get damaged, cause they are being overcharged.
What happens when two chargers are both charging is one will invariably trip to float before the other, when this occurs, it’s output goes to zero, cause it’s putting out a voltage that is lower than the banks, because the other charger that is still in absorption is holding a higher voltage.

AGM banks normally benefit from high charge rates, it’s not bad for them, and of course if you watch, the amps come down as the bank is being charged.
This is not the charger turning itself down, it is the ability of the bank to accept a charge drops the closer to fully charged it gets.


If I had a 1000 amp charger and hooked it to my 660 AH AGM bank and turned it with my bank at 50% SOC initially the bank may take 200 amps, then as it gains in charge, the amps will slowly decrease until 3 is all it’s accepting, at that point the battery charger should trip to float.

However all automatic chargers trip to float prematurely, Main Sail has coined the phrase premature floatation to describe the behavior