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Environmental and cost considerations point towards increasing usage of secondary batteries in the future, rather than primary, "throwaway" batteries. However, the requirement and the logistics for charging facilities for these batteries will have to be addressed. So far, charging facilities are a "third line" responsibility. The widespread use of secondary batteries will require the support of fast chargers (20 minutes to 1 hour charging time) and the logistics of front line charging facilities will represent a serious challenge.
At the present time, the IRIS program of the CF has introduced a rugged NiCd charger for field operation. This charger will charge a fully discharged battery in 3.5 hours. The relatively slow charging time was a trade-off between time and safety for this present generation charger. The next generation of chargers are described as smart chargers. In the case of lithium rechargeable systems, "smart chargers" with voltage/current control of the charging process, will be needed to avoid damage caused by overcharging the battery (lithium rechargeable batteries should not be discharged below a specific cut-off voltage either). Smart chargers usually use pulsed charging currents, rather than a continuous current, and the battery state-of-charge (SOC) is periodically determined between pulses.
The state-of-charge is another important aspect when dealing with batteries. The incorporation of batteries in small arms will make the knowledge of the SOC a critical issue. In the field, a battery that suddenly goes dead is not acceptable. To determine the SOC of a battery that has a flat discharge curve with a rapid drop-off at the end of discharge is not an easy task. Sophisticated SOC meters are now being marketed, but their reliability is not yet known. Batteries that have a sloping discharge profile can have their SOC assessed from an on-load voltage measurement. However, batteries with a steeply sloping discharge curve may not be appropriate for certain circuitry that cannot function below a particular voltage. The proliferation of too many electrochemical couples with different operational characteristics should lead to some rationalization in the near future and the adoption of a Universal battery.
