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post #8 of Old 12-09-2008
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Traditional wisdom for wet-cell batteries is not to charge at more than 20% of the battery bank capacity as a maximum charging rate. You can charge at a higher rate and get away with it...but it generally isn't too good for the batteries. AGM batteries have a much higher current acceptance rate and can often be charged at closer to 50% or so of battery bank capacity.

Some of the newer technology batteries can be charged at even higher rates.
Originally Posted by Omatako View Post
So based on this, 4 Trojans would be 450 amp hours so the charger should not exceed 90 amps? That's a worry.

I have only four T-105's in my house bank. I also have a Freedom 25 charger. I also have a 185 amp alt on my main engine which routinely pumps 140 amps into the house bank when it's a little soft. I can't say I've ever had an overcharge situation because of this. I monitor the whole lot via a Link 20. My batteries aren't gassing and I'm not losing a lot of water.

Most cars have a 65Ah battery driven by a 55 amp alternator. That's quite a bit more than 20%. Most are wet cells.

I always thought that the regulator decided what amperage was delivered to the batteries. Not the charger.

Am I wrong? Again?


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Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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