Charge controller

198

04:01:55

When source voltave raises above 13.2 volts, relay accuates allowing sec. battery (represented by cap) to charge. Once source volt drops below 12.8, relay releases, and led represents drain on secondary cell(while source remains isolated). Purpose for maintaining lvl of secondary batt; allowing secondary circuits to deplete its pwr source without depleting primary batteries, a.k.a. the one that starts my car... PLEASE CRITIQUE, trying to bld a minimal and reliable circuit.

published 10 years ago

tectak

10 years ago

Your circuit works but it has problems. If the battery voltage us at the "knee" , the switch point, for some times you will dissipate a load of watts in the transistor driver.You need a very small hysterisis to stop this. That is why I used an opamp. With the positive feedback loop you can set a small amount of hysterisis. Also, to prevent hunting a capacitor CR delay is introduced to prevent the relay deenergising at short engine switch off. You should also have a base-ground resistor on the transistor, say 22K0 to prevent leakage or pickup. You only need a in4001 rec across the relay coil to prevent back emf damaging the transistor...unless you have some hidden reason?

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