Instructables

24V Battery Charger Schematic

Picture of 24V Battery Charger Schematic
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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Dyk2 hours ago
what do i need to do to be able to use this charger to charge a 100A 12V SLA battery?
novice291 year ago
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
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.
jackthelad10 months ago
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'?
grateed10 months ago
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?
grateed10 months ago
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?
asa196411 months ago
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.

asa196412 months ago
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.
sanmlight1 year ago
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
rameez441 year ago
can we use IRF250 Mosfet instead of IRF250 in 24 v battery charging circuit??
asa19641 year ago
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.
tsitsios1 year ago
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
Hi max,
for 12v changer, are you mean that D7 replace by 6v zener diode?
nazirm1 year ago
Hi Maxolous:
1. You mentioned that during float charge stage U2 switches on and short circuits gate voltage of Q1 - but there is a diode D1 which is isolating base of Q1 from U2 and so how will U2 short circuit Q1?
2. Also, in current limiting stage U1 shorted the Q1 gate and in float charge stage U2 has shorted the Q1 gate. Then I would expect Q1 to behave in the same manner in both phases. Please help me understand here. Thanks
Nazir
nazirm1 year ago
Hi Maolous:
I have one more question. In your notes aobe you have mentioned that U1's Vbe will be 0,7 if the volatage drop across R1 is 0.7 volts. Should we not add the voltage drop across R2 which is 20K and even a low current will give significant voltage drop.
nazirm1 year ago
Dear Maxolous:
Thanks for sharing the circuit. I have few questions:
1. Can I use IRFz44N instead of IRF260? Looking at the datasheets it does not look like a problem.
2. In the text above in your formula I=0.7/R4 -- when I look at your circuit I think it should be R1.
3. In your circuit you have indicated R1 to be 0.1 Ohm. So using the formular 07./0.1 gives 7 AMPs. I am assuming the 24V battery is 100-150 AMPh. If 50% of the available power is drained, then the battery will take 7- 11 hours to charge. Is this calculation correct?
piragash2 years ago
hi every body i am piragash form srilanka so i have solar & battery i wont solar battery charger controler

i have 150amp*2battery total 300amp i need charge solar to battery
plz help me i wont charger circuit
tplim piragash1 year ago
Go to this link http://www.instructables.com/id/How-to-make-any-home-appliance-into-a-solar-electr/
Think this is what you want.
tplim piragash1 year ago
Hi piragash, go online ask uncle Google. Used keyword "charge controller".
novice291 year ago
can some please throw some light
computek2722 years ago
This circuit looks like something that would work for my project...

Three questions:
1. Can this circuit be made to run from a 24 VDC regulated power source that is already supplied?
2. Can an LED be added to indicate if no battery is present?
3. Can an LED be added to indicate the battery is charging?
I'd also like to add a relay to #2 and #3 to turn on two pins on a microcontroller when the proper statuses are reached.

Thanks!
maxolous (author)  computek2722 years ago
1. Yes
2.Yes at the terminals of batteries and has to be given current limiting resistor.
3.Yes
Hi Max,

If I plug it in before connect it to the battery, it will not charge it. I guess because the input voltage is about 30-33V without load. Do I miss something?

Les
Cool! How would I tweak the schematic to do #1 and add #3? Thanks.
maxolous (author)  computek2722 years ago
If you want to run it from 24V regulated power supply, you need to remove the transformer and Rectifier Diodes only

There are so many ways you can achieve this , the simplest is to put LED across the charging terminals,also put a 2k2 resistor in series with the LED to limit current. you will observe that when it is not charging the LED will not glow reason is that MOSFET is not switched.Otherwise, u2 had switched to short cct the gate of mosfet to earth. see the text above.
One more thing: Is there a equivalent to the BZV80 diode that I can use? I can't find that diode anywhere.
maxolous (author)  computek2722 years ago
That is a 6V zener Diode.
regards
Alright, thanks! I'll have to order parts and give this circuit a try.
la5tia2 years ago
Hi Mr. Can you please help me to change the components so this circuit will charge a 32 volt 150AH battery bank. (I suppose it should be charge current of max 15 amps) In advance Thank you.
Kind regards, Terje.
sarco2 years ago
How to add delay rc timer for about 15 seconds to this circuit to use the same h bridge of the inverter for charging without burning the bridge
maxolous (author)  sarco2 years ago
your delay timer has to be switched on by your 220v or 110v relay that you had before now installed in your inverter, (so when making choice of your 220 or 110v relay ,make sure you get the one with multiple throws) by helping you pass your batteries voltage to the delay circuit, it also depends on the numbers of batteries you are using.if you are using battery voltage higher than your delay cct voltage then, you need to regulate it.

Your delay timer which of-course has a relay should pass your mains into your center tap of the high voltage side of your inverter transformer when in operation. I believe you know what i mean.
asa19642 years ago
Hello Maxolous, can you give to us a modifications circuit that can work for 48V and 60V battery charger.

Thanks for your good Jobs.
stephan0072 years ago
Hi Maxolous
Could you please modify this circuit for operating at 26V 4A.
As i have a battery which needs a charger of this rating.
I would be grateful if you help me out.
arjan_al2 years ago
Hi Max,
Can i use this schema to charge a 24 v 80 AH battery?
maxolous (author)  arjan_al2 years ago
yes
Hi Max,
I have a Deca CLASS 16A charger:
http://www.decaweld.com/default.asp?cmd=getProd&cmdID=1997

It seems that isn't an automatic charger(have only a zener diode) but i want to use it all the time(the battery 24 v 80AH will stay connected always).
I would like that when the battery is fully charged, the charger should not continue to charge it.

How can i modify it using your schematic?

Thanks in advance
maxolous (author)  arjan_al2 years ago
Arjan_al ,

The only way i can help you modify is when i see the schematic of your said Deca 16A charger.
max i have been follwowing ur responses and also your images of the inverter, I am inlove with your design. But pls I will like to request from you a low battery warning circuit for a 2KVA/24VDC inverrter which i can incorporate into the PWM inverter circuit posted by nick. Thanks
maxolous (author)  kcgeorge2 years ago
Hello Kcgeorge, I have today 6th mar,2012 designed a circuit for you to meet your need. You can use it for 12v or 24v inverter low-battery alarm. To set this you need a variable Dc power source up to 20v. For your 24v inverter , put 20v source across +ve & -ve of the circuit and vary pot. to the point you hear the buzzer. for 12v inverter put 10v across +ve & -ve and vary pot. to hear the buzzer.

Or run Inverter and monitor with voltmeter across inverter batteries till inverter battery drain to 20.5v then, vary pot to the point you hear buzzer sound lowly

741 is a Voltage comparator pin 3 is the non inverting input while pin2 is inverting input
if the voltage in pin 3 is higher than pin 2 the o/p will be high which ofcourse cannot switch PNP transistor. but, when the i/p in pin 2 which is preset by R4&R5 is higher than i/p @pin 3 due to the fall on battery voltage , the o/p will go low thereby transistor is switched and buzzer comes ON
12V-24V Inverter low battery alarm circuit.bmp
Dear Max,
In order to change "The float charge stage come to play when the Battery Voltage builts up to 28Vdc" float charge stage from 28 Vdc to 27 Vdc,which resistor shoul i change(R6),and how should be the value?
I builded your schema but led comes on although the battery is not connected,is it ok?
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