WAS: ParalChargContrls (Abyss)

[RogerAS]

Abyss (and all),

You wrote in another thread:

"If you intend to run the battery at float mostly and use it for standby power, then 13.6-13.8v will be just fine. My 7Ah 12v SLA used to draw about 30mA once charged to stay at float."

The statement above made me think about something I really never understood very well, and still do not (thus the ? ).

Does this float voltage and 30ma current specifically, indicate or is a factor of, battery internal resistance?

Doesn't lengthening the battery string to increase system voltage also increase internal resistance?

I know adding resistors in series in does this and have made specific resistance circuits doing this, such as precise time divisions on a 555.

Would this be a precise way to cipher this internal battery resistance?

Say 13.8 X .03 amp = 0.414 watts

Can we then determine the battery(s) internal resistance from that wattage number, and what would the math be for that if possible?

Would this be a better way to measure the actual battery state of charge, by adding the resistance factor unique to the battery in question?

Does rising or falling internal battery resistance an indicator of battery life in any way? (other than open or shorted)

Thanks,

[moviequote]

"Oh, Deep Thought (abyss) do you have the answer to the question?"

"Yes, but you're not going to like it".

[/moviequote]

[AbyssUnderground]

I have never looked into battery internal resistance so I can't answer the question without doing my own research.

I should say though, the 30mA figure was a fully charged battery sitting at float (13.8v).

[DamonHD]

I suggest that this is just energy being 'wasted'/dissipated in the battery directly as heat or by causing some electrolysis (and then recombination, giving heat).

Rgds

Damon

[chabitus]

I have 2 batteries that don't seem to want to reach a high voltage on the charger, even with a higher rate of amps. They read a proper state of charge except that they seem to drop a bit (12.7v,12.9v).

Basically, they charge fine for a few hours, then start to warm up but at this point the voltage doesn't seem to rise as it should.

Could this be from sulfation?

I was wondering if i could keep them on a low curent charge (250ma or so) for days in hopes to get the voltage to rise without getting them warm?