8-V 2.2 AH Li-Ion battery with stepped charger and load compensation

Two rechargeable 16850-sizeLi-Ion cells are packaged in a small box with a charger controlled by a PICAXE 14M. The battery may be used without charger input: the output plug is connected to the battery via a fuse and switch. An isolating diode prevents the battery from discharging back into the charger.

When the charger has input, the control circuit is energized and controls the charging current according to the battery voltage.

It may also be used as an Un-interruptible Power Supply. The battery current is measured and the current taken from the charger input is controlled so as to maintain the correct battery charging current regardless of the load current.