Scheme of the Car lamp charger is shown in above. A distinctive feature of the scheme is that the battery will never recharge. This Car lamp charger circuit is built into the “Chinese” lantern, which originally had 4 batteries.
Setting is disabled by batteries and lamps and installed R4. Potentiometer R3 R4 installed on the findings the voltage rate of 1.4 V * N, where N – number of batteries in the lamp. When these nominals used battery capacity was 450 mA • h to 1100 mA • h (I have two of these lamps – one I use in the car as a carrier, and another at home).
R2 – limits the charge current when the discharged battery.
Selected based on battery capacity and is short-circuit 1C.
VT1 – pnp transistor either medium or high power.
VD1 – to stabilize the the voltage of at least one Uakk V.
R4 * – only needed for setup, and then removed from the scheme.
You can use other conductivity transistors (npn), then you need to deploy a zener diode, change the battery polarity and voltage are reversed. If the Car lamp charger input diode bridge set – that can be served from 12 to 15 V in either polarity, or even recess!