Battery Voltage difference???

[monogram]

Hello,

I had 2 battery bank at 24V, each bank consisted of 4 x 6V GC2. I bought all 8 batteries from Sam club back on April 2018; 4 batteries has manufacture dated 1/2018 and the other was 4/2018

Today is the first time I measure the voltage on each cell with the readings below:

- Bank 1:
BAT1: 1.72; 2.15 & 2.09V
BAT2: 1.72; 2.15 & 2.09V
BAT3: 1.72; 2.10 & 2.11V
BAT4: 1.72; 2.15 & 2.11V

- Bank 2:
BAT1: 1.78; 2.14 & 2.15V
BAT2: 1.79; 2.17 & 2.19V
BAT3: 1.76; 2.17 & 2.17V
BAT4: 1.78; 2.18 & 2.18V

Does voltage look right on each cells?
why the voltage on the firt cell looks different than the second and third cell?
please help.

[SunEagle]

I think you are seeing unequal voltages between the cells based on how you maybe charging and discharging those batteries. They should all be much closer in values across the 3 cells.

[monogram]

What caused the cell voltage to be different and how to fix it?

[SunEagle]

What caused the cell voltage to be different and how to fix it?

Either the lower voltage cell is not getting the proper charging or is being discharged at a higher rate then the other cells.

You can try to charging each "24v" bank separately using a quality battery charger and see if the cells get back close to one another or break them up into pairs and try charging them separately at 12volt.

If the batteries aren't sealed you can check the specific gravity of each cell to see what it's status is. That is better then just measuring the voltage.

[monogram]

Currently, I has 10 AWG from charge controller to the battery, is it correct size? (the maximum load that I use is about 11A)

Will the wire between each battery caused the problems?

What is the correct AWG size for for the wire between each battery?


The batteries are not sealed, it's GC2 from Samclub. In the past, the highest gravity that I can see is at 1250.

Normally, each battery bank reach 28 to 29 Volt at around 1PM and it will stay on that voltage for 3 hours before it enter the FLOAT (as setting on my controller)

[SunEagle]

Currently, I has 10 AWG from charge controller to the battery, is it correct size? (the maximum load that I use is about 11A)

Will the wire between each battery caused the problems?

What is the correct AWG size for for the wire between each battery?


The batteries are not sealed, it's GC2 from Samclub. In the past, the highest gravity that I can see is at 1250.

Normally, each battery bank reach 28 to 29 Volt at around 1PM and it will stay on that voltage for 3 hours before it enter the FLOAT (as setting on my controller)

A 10 awg should handle 30 to 35amps depending on the distance. It is best to size all of the wires between the battery and inverter the same size based on the maximum amps the inverter can draw.

ie. 2000watt inverter at 24volt can see as much as 83 amps which would require at least a 4 awg size wire across the battery and inverter connections.

If you can measure the SG of each cell then do that and see if there is a wide discrepancy between cells similar to what you see in voltage. If the SG is pretty close to one another then I would ignore the voltage measurements. If the SG varies like the voltage you have an issue which could require you give all of the batteries a heavy charge to de-sulfer the plates and bring the SG's back to as close as equal across the cells.

[gonavy27501]

Great explanation of varied cell voltages due to unbalanced battery charge/discharge:

http://www.smartgauge.co.uk/batt_con.html

[Sunking]

Today is the first time I measure the voltage on each cell with the readings below:.

Perfect plan to destroy batteries. The very first thing you should have done if you cared about your batteries was to Equalize them to fully charge them, and check them weekly with a hydrometer and volt meter. Instead you decided to try to destroy them with neglect.