paralelling charge controllers

Re: paralelling charge controllers

The voltage error generally comes from large currents going through small wires... So, that is why it is recommended that you create a "battery bus" which is a very low resistance path directly to the battery / battery bank.

Instead of, for example, running a separate light weight cable from the battery to one charge then some more distance to a second charger. In this case, the second charger would be seeing the voltage "increase" caused by the current supplied by both chargers--and possibly under charge the battery.

For larger charge controllers (and computer power supplies), you will find that they have a separate battery voltage lead (like a remote volt meter). You can tie these directly to the battery bus--and no matter how much current/voltage drop you get in the cable from the charge controller to the battery, you will be measuring the "true battery voltage" rather than battery voltage + wiring drop. But, unfortunately, I don't see these remote sense leads on the more popular solar charge controllers--so your best bet is to use large diameter cable and short runs between the charge controller and the battery bus connections.

And, since we are talking about accurately charging a battery--you will want to get a charge controller than has a remote battery temperature sensor (sometimes called a BTS). That too ensures that the battery / bank is being properly charged.

The battery voltage itself also changes with charge and discharging currents--but the charge controllers are programmed to take into account (the best they can) the charge voltage and current to ensure that the batteries are quickly and safely charged.

-Bill