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I have a 300Ah battery which is near-dead (Abused in the past, around 5 years old) and want to replace it with 4-6 new 100Ah. The current method of charging is with a 30A MPPT solar controller.

As the sun starts rising the panels start charging it, but they start with a trickle and work their way up to around 25A.

My question is, is this method of charging OK (start slow and build up)? Or should I disable the charger until there is more likely to be full-sun and charge it harder to start? I don't mind buying more panels and a bigger charger if I need to.

I can control the charger with an Arduino and the home automation system I have, so that is not a problem.

With the next setup I don't discharge it below 12.1V under load, 12.2V at rest, so new batteries will not get abused.

Thanks in advance.

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  • \$\begingroup\$ Sure, that’s how major brands do it. \$\endgroup\$ – winny Jul 3 '18 at 21:12
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I don't see a problem with trickle charging lead-acids. If you get a 400-600Ah pack, you won't get up to the recommended 10% CC mode anyway since your panels deliver 25A max. As far as I understand, trickle charging should be more efficient as well since there is less heat being dissipated, if I'm not missing anything. So your setup looks ok to me, although you won't be getting the maximum amount of power that you can store from the panels.

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