Simple 24V Battery Charger


Introduction: Simple 24V Battery Charger

Charger characteristic
1. Can deliver a charging current up to 20A (claiming 50Amps is doable when designed properly)
2. Automatically turns off charging when fully charged voltage is reached (protects the battery from overcharging)
3. Simple and minimal parts

Part List:
R1 - 20 kilo ohms 1/4W
R2 - see Charging current vs R2 abovefor more info
R3 - 2 kilo ohms 1/4W
R4 - 10 kilo ohms 1/4W
R5 - 2 kilo ohms 1/4W
Q1, Q2 - 2N2907, CS9012, 2N4403 or similar PNP transistor
Q3 - 2N2222, CS9013, 2N5551, or similar NPN transistor
Q4 - FQP27P06 or any P-channel Mosfet with higher capacity
Dz - 1N4750A, or any 27V zener diode
DC - 30VDC, 20A max AC-DC converter or DC power supply

Charging current vs R2
1 Amp - 0.7 ohms rated 1 Watt
5 Amps - 0.14 ohms rated 5 Watts
10 Amps - 0.07 ohms rated 10 Watts
15 Amps - 0.047 ohms rated 10 Watts
20 Amps - 0.035 ohms rated 15W

Note: the charger schematic is originally from



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    I like it, but what kind of bateries is capable to charge?

    Plese tel us what is need to make 40 amps output. Need to charge wet cells quickly. ThankYou. Danknww

    Can someone give me the component values so I could build this to recharge my 18v power tool batteries?

    the Resistance of R2 is 0.66ohms to flow approximately 1A current.

    i've implemented this circuit to charg my 24v battry(two 12V seald lead acid battries in series) but it is not charging the battry.

    i just connect a blue LED in series with 3.9k ohms resistor at the collector of Q3(im using C828 NPN) the voltages at the collector of Q3 are 37.4V(as 42.3V is the DC in) the base of Q1 has 41.6V and its collector has same 42.3v(DC in) and also at collector of Q2 and the base of Q2 is also 42.3V. the collectors of Q1 and Q2 are at 41.4V that are feeding at the Gate of MOSFET Q4(im using IRF9610) the source of Q4 is at 42.3v(DC in) while drain is consistently delivering 20.8V at output(either battery is connected or not). my batteries are also discharged and giving 20.8V at output.

    i check my circuit on bread board many times but i m unable to find the fault. hope you will help me.
    Thank you

    Dear markee2

    This circuit it can charge dry battery


    me i want simple than this please.