Posted by sotxbill on January 06, 2023 at 08:02:02 from (172.56.88.179):
In Reply to: Re: Amps vs volts posted by MarkB_MI on January 05, 2023 at 06:59:29:
Dont know... but...
AS THE BATTERY IS CHARGING... you can.. safely measure the current going through it... and the voltage drop across it... say its now at 14 volts and taking .5 amps... ohms law says..... you now have a 28 ohm resistor as far as the charger sees. or 12 volts and 25 amps...equals a .48 ohm resistor to the charger. ( in this case, the resistance could actually be lower but my charger is regulated to 25 amps max)
Sulfate on the battery plates and other things control the total resistance to the outside circuit in addition to the cells themselves..a battery is a chemical resistor... that takes a lot of charging for the chemistry to change with losses in heat. And slowly the voltage rises...... TO a primitive fixed voltage charger... its ohms law.. including the internal limter resistor of the charger to control max current into a almost short of the battery... thus were limited in total current. Was common in the on the older chargers to pop the charging breaker when put on a dead or almost full short of a battery. (ohms law) If not enough charger resistance, then a timer installed to keep from over heating the battery. Modern circuits with voltage and elegant current regulators are better as current of the charger cant be exceeded, and then voltage is limited as the battery comes up...... then the 3 stage systems with cpu control are best yet. If batteries did not have internal resistance, they would continue to charge at max current forever from the chargers standpoint. So.. to the charging circuit, a battery is part of a chemically varying resistor in a circuit.. and ohms law works. my best guess.
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