IEC TS 61044:2021(E) covers opportunity charging of lead-acid traction batteries, i.e., the use of idle time during a working period to increase the state of charge (SoC) so as to extend the daily working period of a lead-acid traction battery while at the same time avoiding an excessive depth of discharge.
This document specifies requirements for the use of opportunity charging of lead-acid traction batteries of vented and valve regulated types when the battery manufacturer has not provided alternative specific operating procedures.