Charge two batteries one controller

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Hi Doc,

A number of people who do not fully understand electricity will insist that both batteries be identical specifications and of the same age. Sure, if you do that then you are acting safely. However, there is no real need to do that.

Connecting batteries in parallel for charging requires only that they be of the same type, i.e. both AGM's etc. Differences in the two batteries such as capacity or brand may result in differing current acceptance during charging but they will eventually both reach full charge at the same time.

Of course, there is no problem at all during the battery discharge. Each battery will contribute proportionally (but not identically) to the load and will maintain the same DOD (depth of discharge percentage)

The only issue with paralleled batteries is that when one battery becomes faulty, due to say internal discharge, it will sap energy from the good battery during standing.

So go for it. just be sure that they are the same chemical types.

The upstream battery will get worked harder than the downstream so put the younger one there when you install them.

I have a 40amp Redarc bc/dc charger looking after 2 agm batteries hooked in parallel with each other a 105ah Amptec form Autobarn and a 105ah Giant from Aussie batteries no problem yet.

Whoever told you the batteries must be the 100 percent identical was misleading. I believe you have a solar panel controller and it theoretically can charge any lead acid batteries, that includes gel, AGM, deep cycle.

There is, I guess, only 1 thing to be noted in prior to your set-up, you need to check the operating voltage on both batteries. It's always better to catch up with same voltage level. Like I've got two AGM forming a dual batteries system, different models but they are 13.2V-13.7V ordinarily.

Even you've got 1 AGM, 1 another type, that really doesn't matter. Just make sure your redarc controller has been correctly connected.