PD IEC TS 61044-2021 Opportunity charging of lead-acid traction batteries.
4 Planning the implementation of opportunity charging
The following list items a) to c) shall be considered when planning to introduce opportunity charging.
• Indications that opportunity charging may be beneficial are:
a) when the maximum permissible physical size of the battery for the vehicle does not have enough capacity to complete the daily workload before a next complete recharge becomes necessary. This allows an undesirable physical change-out of the battery to be avoided.
b) when the operational requirements of the vehicle are such that it is impossible to predict when the battery will next be released for a complete recharge. This can occur for example in locations such as airports where 24 h per day working is a rule.
c) when a battery is close to the end of its operational life and the use of opportunity charging can be shown to maintain an acceptable performance of the vehicle.
An implementation of opportunity charging will result in an additional energy turnover in the battery beyond the 60 % or 80 % limit per cycle specified by the manufacturer. This change in operational mode is therefore to be cleared beforehand with the battery manufacturer as it is possible that this will have an impact on warranty terms and conditions.
NOTE 1 If the periods available for charging are of short duration and infrequent, then opportunity charging will be of little benefit.
NOTE 2 When opportunity charging enables the user to discharge substantially more than the recommended percentage of the rated capacity each day, the battery-life measured in years will be reduced as the battery-life measured in terms of cumulative ampere-hours discharged is approximately constant.
NOTE 3 Opportunity charging at a SoC > 70 % is less effective and can result in a significant increase of battery temperature, gassing, water loss or sudden failure of VRLA designs.
NOTE 4 Opportunity charging results in higher electrolyte working temperatures that accelerate battery ageing.
5 Operational procedures
The following information in 5.2 to 5.5 shall be considered when operational procedures are being established.
5.2 Charging conditions
Self-compensating chargers are preferred when opportunity charging is carried out. A correctly sized battery and charger combination is essential for all batteries.
For opportunity charging of valve regulated lead-acid batteries it is essential that onlychargers with a current-voltage-time characteristic in accordance with the battery manufacturer’s recommendation are used.
In order to maximize the beneficial effects of opportunity charging, such an operation is preferably carried out only when the fully charged battery has been discharged by at least 30 %of its rated capacity.
This limit is especially important when vented lead-acid batteries are charged with non-self-compensating chargers. Non-self-compensating chargers shall not be used for valveregulated lead-acid batteries.
For intensive energy throughput applications with expected high battery temperatures,opportunity charging shall be initiated only when at least 40 % of the rated capacity has been discharged from the fully charged battery.
An air agitation system of the electrolyte is highly recommended for vented lead-acid batteries in order to prevent acid stratification and to improve the efficiency of the opportunity charging.
Where a known duty cycle exists, a calculation of the energy balance or ampere-hour balance is recommended. The availability of adequate charging time and intervals for opportunity charging shall be verified beforehand.PD IEC TS 61044 pdf download.