I have two solar arrays which totals close to 2 kw that I use to charge a 24 v 450 amps flooded lead-acid battery bank using 2 mppt charge controller of 30 and 40 amps.

Will it damage the battery by charging it too fast?

  • I'm assuming you have a properly sized and configured charge controller charging your batteries. If so, them it's not a problem. If not, then yes, you are likely damaging them.
    – jwh20
    Mar 7, 2020 at 19:28

2 Answers 2


Those MPPT controllers seem appropriately sized compared to panel capacity. The panels might output slightly more under absolutely ideal conditions, but those are rare.

70A into a 450 amp-hour battery means you would recharge them from zero in 6.5 hours (which you should not ever do, allowing lead-acids to fall anywhere near zero, that is).

So your charging rate is 0.1555 "C", which is high, but still within limits for lead-acid. It may tend to heat up a bit given the fairly fast recharge rate, which may cause high water use. Be careful; use distilled water for makeup water, because if you're frequently adding water, that means any impurities in the water get concentrated fast.

  • 1
    Letting even a deep cycle drop below 50% charge will do more damage to the battery than charging a 450 at 40 amps. A flooded acid description is not enough info, they should be deep cycle at a minimum but if deep cycle / starting batteries they can handle a larger charge / discharge rate. The last set of batteries I installed recommended 70% max discharge level.
    – Ed Beal
    Mar 8, 2020 at 8:17

It could not only damage the battery.

As already mentioned, fast charging of non-defective flooded lead acid batteries with high currents is normally no problem - given the charger meets the lead acid charging regime and all cells and charger are working properly - and the room is vented without discharges from static electricity or sparkings, overheating etc.

Otherwise it could become a safety problem. Some lead batteries produce H2 and/or O2 during charging. And in case of defective cells or chargers that do not fail safe.

Both gases are a very explosive combination. The engine room in a car is always vented.

H2 alone has a big explosive limit range, i.e. the percentage interval of H2 concentration in air to yield an explosive mixture is roughly 5 to 75 volume percentage.
For comparison, gasoline has a range of 2 to 10 vol-%.

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