Electric Vehicle Discussion List - Voltage vs SOC for USBMC golf car batteries

Voltage vs SOC for Flooded, Gel & AGM Batteries
From the East Penn technical manual for Deka Dominator gel batteries

Open circuit voltage is inferior to specific gravity as an indicator of a lead battery's state of charge (SOC). But you can't measure SG with closed (valve regulated recombinant, or VRR) batteries, so voltage is all you have to go on.

The table below describes SOC estimates for a 12 volt battery after at least 8 hours of standing off charge and unused.

State of Charge Voltage

Flooded Gel AGM

100% 12.60 - 12.70 12.85 - 12.95 12.80 - 12.90

75% 12.40 12.65 12.60

50% 12.30 12.35 12.30

25% 12.00 12.00 12.00

0% 11.80 11.80 11.80

State of Charge	Voltage
State of Charge	Flooded	Gel	AGM
100%	12.60 - 12.70	12.85 - 12.95	12.80 - 12.90
75%	12.40	12.65	12.60
50%	12.30	12.35	12.30
25%	12.00	12.00	12.00
0%	11.80	11.80	11.80