I install residential security alarms in California. As you may have heard the area is now subject to prescribed blackouts by the power companies to reduce fire ignitions during periods of high wind. The alarm systems used have backup batteries that will run roughly 1 day before being depleted (12v 7ah). The blackouts can be several hours to a week. The alarm panel has a trickle charger to freshen the battery in normal service but according to the panel manufacture it will not effectively charge more than 2 of the 12v, 7ah batteries in parallel. I would like to use a much larger battery with a more robust changer. What are the consequences of 2 chargers feeding the same battery? Is there a need to or a way to isolate the charger in the alarm panel from the second charger.

 

Most likely, the currents would simply add, but it depends on the design of the charger.

Bob

 

You can use Diodes to steer the chargers together to prevent back feed, otherwise just parallel them together.

 

Thanks Bob and Dave. So it sounds like since the chargers are roughly the same voltage that the circuit will see when the battery is powering the device during a power outage and there is no risk of the higher current charger burning the trickle changer that is built into the security alarm board.