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Old 07-15-2013
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Re: m25 alternator question

I think I was actually trying to say pretty much what you just did, except that you explain it better. I am fully aware that an alternator simply outputs a voltage, but my point is that a shore charger may output a higher absorption voltage BECAUSE it will switch to trickle when absorption is done. An alternator will not switch, so there has to be a compromise in the absorption voltage, so as to not cause excessive electrolyte consumption over the long term.

You didn't mention the thermal compensation in most alternators. Mine will start out at 14.4V, but once the engine has run for a while and the engine compartment has warmed up, the output will drop to 13.6V or so due to the alternator's internal compensation reacting to the higher temperature. So I'm never going to reach 100%, and 85% is a good assumption. Suits me, as I hate topping off the battery electrolyte.
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