Energy Control For Battery Chargers

P 1 R9 12V R4 039 ENERGY CONTROL FOR BATTERY CHARGERS R3 85 11 01C2 D2 D3IRef 1C1 rr= P2 T2 50k R6 R2 00 50k BC517 T1 2 ROR7 1% 9. 10* BC517 •• A1,A2 =1C1 = LM358 mom ELEKTOR ELECTRONICS JULY 1989 SUPPLEMENT 1 1N4001 2V Fl In most automatic battery chargers, the power transformer remains connected to the mains even after the the battery (or bat- teries) has been charged. In many cases, considerable energy sav- ings can be achieved by disconnecting the transformer from the mains when the battery is fully charged. This circuit performs this function for 12 V car battery chargers. The battery voltage is monitored by an adjustable window comparator around opamps Al and A2, which are powered by a stabilized supply voltage of 8.2 V (R7-D1). The high and low switching thresholds, Urti and 1.11., are set by presets P1 and P2 res- pectively. The reference voltage for the opamp is obtained from junction R1-R2 and is a function of the battery voltage. With the given values of R1 and R2, ...