# 24V Battery Charger Schematic

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The battery charger is originally designed by me to meet the need of some who want a 24V battery charger.
The charger is in three stages; the power source, current limiting and float charge stage.

In this design, 240/24Vac(rms) transformer was used. After rectification and filtration i got about 30Vdc.Therefore the transformer and diode rating should be well chosen to meet your demand

At the current limiting stage , transistor U1,Q1 and resistor R1 plays the vital roll in the current limiting; When U1 switches on it short circuits the gate voltage of Q1 thereby restricting current flow through the battery under charge. U1 will only switch when Voltage across it's base-emitter Vbe is up to 0.7V. the voltage drop across R1 determine this,if the voltage drop across R1 is up to 0.7V then U1 switches on then, I(current thru batt)=0.7/R1(sense resistor). Ohms Law.

The float charge stage come to play when the Battery Voltage builts up to 28Vdc. In this design once the voltage gets to 28Vdc, it is considerably large enough to make the zener diode reach it breakdown voltage. And once this is done U2 switches on and consequently short circuit gate voltage of Q1. The charger is now said to float charge.

The LED comes on when the battery is full.

Note: In most cases D6 is chosen to be 10v but, 6v can be chosen for logic MOSFETs. And this current limiting circuit only allow N-channel MOSFETs

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## 112 Discussions

Where can I get a replacement transformer? There are no identifying numbers on the transformer itself.

Can anyone tell me if its possible and how I could modify this circuit to become a pass thru charger. So that I can charge two 12v BB-2590 batteries while connected to shore power and run the system and when I disconnect from shore power it kick to the batteries.

I have 4 batt each 2 conected in series and each group(2 series batt)conected in parrellel each batt is 12v 110amp and my source 115 ac volt 60hz how can i use this circiut to charge my batteries

Hi! > Max, can ask something regards for this circuit, what is the maximum input voltage for this schematic diagram?

i am a novice as for as electronics is concerned.
I have built a charger on bread board. it does not work . I have following observations ;

1.the LED comes on as soon as charger is switched on with or without load
2.there is no output on mosfet drain. i used IRFP260N
3.voltage accross the base and emmiter of U1 is 0. voltage across emitter and collector is 0.7 v.
4.voltage across R3 is34v(my input is 35v rectified and filtered )i
5. my C2 is a 100 nf capacitor. 10nf was not available.
6.what is the function of 6v zener diode

i do not know how to trouble shoot can you guide me please

2 replies

10volt zener is switch on the moment 24volts appear in its battery terminals

in effect, the mosfet Q1 is already @ Floating mode meaning a very small amount of current is fed to the battery even though @ battery terminal is only 24v when we take a voltage measurement.

Now to fix this problem , replace zener diode with 12v rating, and the R5 should be replaced with the exact value or close to 9835 ohms.In this values ,as the voltage of the zener reaches 12v across its terminal U2 will be turned on, LED1 Lights on indicating that @ battery terminal 28volts is reached and the circuit is now in float mode with very minimal current flowing to the battery

i am also make a 24v 7amp battery charger but i have also same problem i am using irf250. also r1 0.1om how many wats resister using please sent me replay about this problem in my gmail account. my gmail address is radhakrish.athira@gmail.com can u send this immediately.

what do i need to do to be able to use this charger to charge a 100A 12V SLA battery?

I have a DC 24v 5amp electric motor taken from an old mobility scooter that had been powered by lead-acid batteries. I need a power supply to run off the mains to drive this motor for a new application. I would like to build my own power supply therefore can I use something like the 24v charger designed by 'maxolous'?

hi sir i want to build this charger but i have a small problem can i use the same inverter transf to charge and can i replays 450 ohms resister with 470 ohms?

hi sir i want to build this charger but i have a small problem can i use the same inverter transf to charge and can i replays 450 ohms resister with 470 ohms?

How can I Cross-connect this circuit with the inverter transformer, in other to use the same inverter transformer to charge the 24Volts battery.
Thanks.

Hello Maxolous,
please, can you send to my mail a circuit diagram of how to incorporate this 24 volt battery charger you design into your inverter circuit diagram to be able to use the inverter transformer to 24v-0-24v tapping to charge the 24volts battery. my mail is adewale012@yahoo.com. Thank you very much. Please I am still expecting your reply. God bless you.

Hi Max,

Can i use irfz44n instead of irf250 for 12v and 24v?
what diode/ampere should i use for 6 and 10 amps transformer?

Regards,
Mike L

can we use IRF250 Mosfet instead of IRF250 in 24 v battery charging circuit??

Hello Maxolous,
please, can you send to my mail a circuit diagram of how to incorporate this 24 volt battery charger you design into your inverter circuit diagram to be able to use the inverter transformer to 24v-0-24v tapping to charge the 24volts battery. my mail is adewale012@yahoo.com. Thank you very much.

Good morning,
I am interested in building a 24V charger implementing the hand sketching diagram.
Have you built the charger following this diagram?
Will this charger be able to pump 30Amps on my battery bank of 200AmpH?

Best regards
Tsitsios