Understanding battery charging

[neildeb2]

I'm upgrading my 32v charging system with a 32v 115amp alternator and a new set of AGM 8v batteries. I found an external voltage regulator that can be programmed to apply the correct voltages for bulk, absorb, float. But I'm having a hard time understanding something:
- if I'm charging the bank of eight 8v batteries at, say, 36.8 volts, how is this ok, when the mfr says max charge is 9.2v per cell? (36.8v is 9.2v x 4 cells in a battery)
- IOW, doesn't each cell "see" 37.5v? Wouldn't that be overcharging the cells?
Im probably over-thinking this...

 

[Boatsb]

I'm upgrading my 32v charging system with a 32v 115amp alternator and a new set of AGM 8v batteries. I found an external voltage regulator that can be programmed to apply the correct voltages for bulk, absorb, float. But I'm having a hard time understanding something:
- if I'm charging the bank of eight 8v batteries at, say, 36.8 volts, how is this ok, when the mfr says max charge is 9.2v per cell? (36.8v is 9.2v x 4 cells in a battery)
- IOW, doesn't each cell "see" 37.5v? Wouldn't that be overcharging the cells?
Im probably over-thinking this...

Get the details correct then see if the math works.

Each cell in the battery is able to take about 2.4 volts.
Each battery has 4 cells.
Each bank has 4 batteries.
16 cells at 38.4 volts max charge voltage.
Charging is done in stages. Bulk and absorption bring most of the power in at higher amperage causing heat. What is the max charge rate of each battery? Can it take the power without cooking the batteries? Hows ventilation? They will out gas into the area and that could make the environment acidic and damage the equipment there.
Will the AC chargers be running at the same time?
It's not as easy as just adding the charging capacity.

 

[Phasma2128]

I might be wrong but I believe the cells in a battery are connected both in series and in parallel. If they were only connected in series a cell might not charge to full capacity if its neighboring cells reach peak charge before it does. Connecting in both series and parallel addresses this. Again I say……I think.

The external posts are connected serially across all cells internally thus 4 x 8volt = 32vdc. Battery chargers typically have a built in safety that prevents overcharging.

 

[Captain Ralph]

The three battery float stages, Bulk, Absorb& Float.
Weeding thru your numbers, 3 Vdc per cell (4 cells to a battery, 4 x 8v batteries per bank) is maxed at bulk charge for a few minutes And could be as high as 49Vdc for the whole bank.
Past Absorption mode to float mode, these voltages and current levels come down.
I keep my float mode down to 2.125Vdc for our float mode, 34Vdc per bank.

If your not understanding battery fundamentals of installing a charging system, Please consider A real marine electric tech.

I have questions for you. Where are your old 30SI alternators? Please don't toss them.
When engines are you starting and what battery brand/model?