State Of Charge Drift
State Of Charge (SOC) is the battery's level of charge, usually expressed as a percentage of full. It is similar to a fuel gauge, such that 25% SOC is 1/4 full. Depth Of Discharge (DOD) is another term used which describes how empty the battery is. DOD is the opposite of SOC. So, 25% SOC is equal to 75% DOD. Since in a Hybrid car the battery is recharged from gas, the SOC usually has a target of about 3/4 full. This is unlike a Battery electric vehicle (BEV) whose SOC would fall from full to empty untill refueled like a traditional gas car.
State Of Charge Drift (as demonstrated by Ron's PriusPlus and also known by Insight drivers as a Recalibration event) is the manifestation of voltage based correction in primarily counter-based SOC calculation algorithms. It can be taken advantage of in PHEV conversions to enable State Of Charge Manipulation which can help improve battery pack utilization.