Charging my alarm backup battery using solar

[atunguyd]

I don't fully agree with you. The way I was taught: If in parallel the most fully charged battery will have the lowest internal resistance and thereby it will always be charged more than the flatter battery. It would have been perfect it it worked other way around but pity a lead acid battery doesn't work that way..

You are not taking into account that the battery with the greater charge also has a higher voltage which acts to "resist" the charger more than the battery with the lower charge.

That being said excluding the charger as soon as you connect the two batteries in parallel the one with the higher voltage (and hence charge) will force current into the other pretty much charging it until both battery's are at the same voltage. At this point they act as one battery with double capacity. Obviously though it will take double the energy to charge them too.



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[Aidanz]

I connected a 110ah deep cycle battery directly to the alarm box. It gets charged by the original alarm power pack. It has been working like that for 2 years now. No problems even after two sessions of stage four shedding in one day.

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