Battery State of Charge Reference
Use a narrowly scoped manufacturer reference at 25°C after at least six idle hours; this is not a universal battery gauge.
A QUICK WALKTHROUGH
How to use this tool
- Choose 12 V Trojan AES/standard AGM or LiFePO4.
- For AGM, enter an open-circuit voltage measured at 25°C after at least six hours with no charge or load.
- Read the reference bracket; use a current-counting battery monitor for LiFePO4.
Exact AGM scope
The five displayed points are Trojan’s AES AGM and standard AGM 12 V open-circuit table at 25°C: 12.84/100%, 12.54/75%, 12.24/50%, 11.94/25%, and 11.64/0%. Values between points are shown only as a bracket, not interpolated.
Measurement conditions
Trojan says an accurate open-circuit reading requires no charging or discharging for at least 6 hours, preferably 24. Temperature changes voltage, so readings away from 25°C should use the battery maker’s temperature guidance.
LiFePO4 boundary
RELiON says a typical lead-acid voltage gauge is not accurate for LiFePO4 and recommends a high-precision battery indicator using instantaneous and integrated data. This page therefore does not convert LiFePO4 voltage to SOC.
GOOD TO KNOW
Common questions
Can I use this for any 12 V lead-acid battery?
No. The built-in points are specifically the cited Trojan AES AGM and standard AGM table.
Why does it not interpolate a percentage?
The source provides discrete reference points, and interpolation would imply unsupported precision.
Can it estimate LiFePO4 SOC from voltage?
No. Use a compatible current-counting battery indicator.