[Float cum Boost charger – Single Battery – Single load without VDD]
The Battery Charging equipment comprises of Float cum Boost charger.
Float cum Boost charger has two modes of operation i) Constant Voltage Float Mode, ii) Constant Voltage / Current Boost Mode (as applicable as per the battery type).
Normally in Float mode, charger will supply the trickle charging current required for the batteries and will also feed the DC continuous load as required. During this time, the charger and the battery are across the DC load terminals. If Battery charger fails, the battery will supply the load through DC contactor.
During an emergency when AC power fails, the battery supplies the load and discharges to certain extent depending upon duration of emergency and the intensity of the discharge current. When AC power is restored, the battery needs to be boost charged for which operate Float cum Boost charger in its boost mode.
When there is a power failure, the battery readily meets the DC loads. When power resumes, the battery has to be recharged for which operate the Float cum Boost charger in Boost mode. During this period of boost charging, the DC contactor will get open & the load will be supplied through Battery Tap diode as per logic provided in charger. Thus, higher voltage during boost charging will not appear across the load. During boost charging, 80% Battery cells get charged & Discharged simultaneously and 20% Battery cells are overcharged since load is fed through 80% tap cell diode.
To overcome on the above, next scheme is Float cum Boost charger – Single Battery – Single load with VDD.