This is the sequential battery battery charger board designed for a marine electronics customer adapting an underwater acoustic telemetry system. Note the shape of the board required to fit inside the cylindrical pressure housing.

The receiver module was to be powered from four diode-connected NiCad batteries. After a period of deployment, the unit would be brought to the surface to recharge the batteries without opening the unit which, in adverse conditions, could compromise its pressure seals.

The batteries used in remote diagnostic medical equipment, principally for aircraft use, need to be fast charged during routine maintenance periods. This custom designed charger is fully SMBus compliant. Housed in a purpose built plastic enclosure, it fully charges a 5 ampere-hour, four cell lithium ion battery in approximately three hours. The PCB layout was done in-house to minimise the area of the high speed switching traces. This attention to detail, together with input and output filtering meant that the unit passed its radiated and conducted interference specification in the unshielded enclosure. With an efficiency of 90% at full load, losses are kept to a minimum and the unit stays cool.

The simple charger is designed around a very low dropout linear regulator. Input is from a 17 volt DC, 30 watt mains adapter which has a universal input voltage specification for world wide use. The charger is housed in an off-the-shelf heatsink box and charges a 5 ampere-hour, four cell lithium ion battery in approximately four hours.