State Of Charge (SOC) determination with NIMH batteries

State Of Charge (SOC) determination  with NIMH batteries
IMA system SOC determination

The terminal voltage of a lead acid or Lithium battery can be used to determine the SOC, since it drops as the battery is discharged.
The discharge voltage of a NIMH pack is very flat, compared with other batteries, so the best way to determine the SOC is to measure the current into and out of the pack. The minimum SOC where one of the subpacks reaches the drop out area of the curve is used to start a forced recharge called a recalibration. The full SOC condition can de measured by watching for the voltage change at the full charge point, as well as the rapid rise in temperature when at that point.