Car battery charger
Description.
Given below, is a very simple circuit that can be used for charging car batteries. In this circuit there is facility for monitoring the charging current and voltage.
The circuit is based on the IC MC78T12ABT from Freescale.The IC is nothing but a 7812 in TO-3 package with 3A capacity. The transformer T1 steps down the mains voltage and diodes D1&D2 does the job of rectification. Capacitor C1 does the filtering and C2 acts as a decoupling capacitor. The ground terminal of IC1 is lifted to 2.1V using the diodes D3 , D4 and D5 . So the output from the IC1 will be a regulated 14.1V (12+2.1).The battery is charged via diode D6.The D6 blocks reverse flow of current from battery to charging circuit when the mains power is not available. Meter M1 shows the charging current and M2 shows the charging voltage.
Circuit diagram with Parts list.
Notes.
- The transformer T1 can be a 230V primary; 15-0-15V, 3A secondary step down transformer.
- The meter M1 can be a 3A FSD ammeter.
- Meter M2 can be a 20V FSD volt meter.
- Fuse F1 can be a 1A fuse.
I need to build my own power supply for 220 volt ac to 12 volt dc around 30 watt is ok,it must be reliable for LED signage,,can I be assisted? Thanks
PLS. HOW CAN I MAKE THE CIRCUIT SHUT DOWN WHEN THE BATTERY IS FULLY CHARGED AND VICE VERSA . ALSO INCLUDING INDICATING LEDS. PLS.REPLY ME. 1000 THANKS.
Hi since this is regulated voltage charger with a flat battery at the start of charging the current will be at 3amps, gradually decrease and once the terminal voltage reaches the rated voltage the current will reduce to minimum and it will be just doing the topping up function, hence no additional circuit is required. regarding the charge indication, replace the link between C2 and D5 connect a 0.22 ohms 5 watt resistance. a BC 547 transistor emitter to C2 & 0.22 ohm junction, base through 100 ohms resistance to 0.22 ohm & D5 junction and collector through LED and series with 2.2Kohm resistance to IC1 ‘in’. The LED will glow brighty to start with and slowly it will dim down as the battery is nearing its rated charge limit.
hi mr peter the above circuit is most suited for your application requirement. by replacing D3 D4 and D5 with a link and also D6 with a link.