question

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finalman asked

Charge Large Amp Capacity Battery with a Small Solar Regulator

Basically I want to charge up four new 12v 330 amp AGM batteries individually before connecting them in series to make a 48v bank. I'm assuming the batteries will come nearly fully charged being AGMs.

I have a spare a bluesolar 75/15 regulator and a 12v 160w panel.

OR

I could remove one of the four of my smartsolar 150/35 regulators battery connections and connect to the new battery. This regulator is connected to 1200 watt solar array on the old 48v bank but would prefer not to if not essential.

Most guides say use a charger with a charging current that is 10% of the battery amp capacity meaning which would be about 30 amp in my situation.

Is the 10% rule correct and I should use my 150/35 regulator or will I be OK with the 75/15 regulator and 160 watt panel?

battery charging
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2 Answers
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kevgermany answered ·

The small controller will be ok, just takes longer.

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finalman answered ·

Yeah the reason they don't recommend using smaller chargers is that the battery voltage is kept higher for longer periods which isn't great for batteries.

Anyway my batteries arrived full because after connecting the 75/15 regulator they were absorbing amps well below the end amps setting so basically went straight into float. After joining them into a 48v bank and connecting them to the four 150/35's and 7kWh worth of solar arrays with no loads they did the same quick absorb to float switch.

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