24V lead acid battery charger circuit
Description.
This lead acid battery charger circuit is designed in response to a request from Mr.Devdas .C. His requirement was a circuit to charge two 12V/7AH lead acid batteries in series.Anyway he did not mentioned the no of cells per each 12V battery. The no of cells/battery is also an important parameter and here I designed the circuit assuming each 12V battery containing 6 cells. When two batteries are connected in series, the voltage will add up and the current capacity remains same. So two 12V/7AH batteries connected in series can be considered as a 24V/7AH battery.
The circuit given here is a current limited lead acid battery charger built around the famous variable voltage regulator IC LM 317. The charging current depends on the value of resistor R2 and here it is set to be 700mA. Resistor R3 and POT R4 determines the charging voltage. Transformer T1 steps down the mains voltage and bridge D1 does the job of rectification. C1 is the filter capacitor. Diode D1 prevents the reverse flow of current from the battery when charger is switched OFF or when mains power is not available.
Circuit diagram.
Notes.
- Assemble the circuit on a good quality PCB.
- T1 can be a 230V primary, 35V/3A secondary step down transformer.
- If 3A Bridge is not available, make one using four 1N5003 diodes.
- LM317 must be fitted with a heat sink.
- R2 = 0.85 ohm is not a standard value. You can obtain it by combining a 6.2 ohm and 1 ohm resistors in parallel.
- F1 can be a 2A fuse.
- To setup the charging voltage, power ON the charger and hook up a voltmeter across the output terminals and adjust R4 to make the voltmeter read 28V. Now the charger is ready and you can connect the batteries.
- This charger is specifically designed for two 12V/7AH/6 cell lead acid batteries in series OR a 24V/7AH/12 cell lead acid battery.
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hi, i built this circuit and its working well ,on testing.
i have few queries.
1) i got a 40 volts 5 amp transformer , is this suitable for charging two 12 v sla batteries, can a high amp damage the batteries.
2) how much time will it require for the batteries to be fully charged.can the charging time be reduced.
thanks
Jan
collector conneted to the led and 2.7k resistor to c1 pos. base connected to 100ohm resistor after r2. emitter connected before R2. same a Q1, just the collector is different.
Please advise what is the modification for charging 4 x 12V-7AH (total 48V-7AH). Thank you.
Hi
”
As the charge indicator is mandatory you can connect Q2 BC547 similar to Q1 with collector connected through an LED and a 2.7K ohm 1/4 Watt resistance to C1 positive. When the drop across R2 is greater than 0.65volt the LED will start glowing.”
Q2 collector connect to C1 ok. Where are connect to Q2 B and E?
Hi Jan it is suitable for 24volt 7AH capacity. (can be 2nos of 12volt 7AH in series)
Hi, is this circuits suitabl for jel battery?
It would appear that the circuit requested by P. R. Srinivas is exactly what I need for a charger for the battery pack for an APC Smart UPS 1500 — two 12v 18Ah sealed lead acid batteries connected in series. Would you please either post the modified circuit diagram or send the diagram and parts listing to my e-mail address which I have sent to you separately?
Thank you for your assistance.
hi, i have a electric bike whose charger got damaged,this circuit fills in for the charger.
Sir,
I can’t design and simulate a circuit to be able to charge battery of 12 to drive a small power dc motor of 9V to 12V wirelessly. with airgap transformer or two isolated induction coils.
Hello Sir, I’m having a BLDC motor now(speci:0.25hp,24vdc,3000rpm).gng to do a project on EV with that motor.First part of it is to design a battery charger..pls guide me what type of battery will be good and also suggest me some circuit to design a good charger for it.. if u mail me I’ll be more thankful to u.. if any details is missing please mail me or post here.. Please help.. my mail id is:vishnukarthick108@gmail.com
Hello Sir, I’m having a BLDC motor now(speci:0.25hp,24vdc,3000rpm).gng to do a project on EV with that motor.First part of it is to design a battery charger..pls guide me what type of battery will be good and also suggest me some circuit to design a good charger for it.. if u mail me I’ll be more thankful to u.. if any details is missing please mail me or post here.. Please help.. my mail id is: vishnukarthick108@gmail.com
Hi CJ you are correct, Mr SOD requires 5 units to be charged that is 5 X 7.2 volts that is 36volts. Drop across LM338n is 5 volt drop across diode in the output circuit is 0.7. hence DC requirement at LM338 input is 41.7 volt at rated load current. Hence a 30Volt RMS at rated load is sufficient.
hi there,
Why we need to use a 35V,3A transformer?
charging voltage is 27.6V,
peak voltage input for the lm317 is 35×1.414=~49V
49-27.6-0.7=20.7V drop across the lm317?
~14w drop on the lm317?
Can we use 30V transformer?
Correct me if i am wrong.
thanks^^
Hi Soo the above circuit will do only the open load out put voltage to be adjusted by 10K pot to 35volts before connecting the battery.
I need to charge 5 units x 6V 12AH SLA batteries for backup. What modifications need to be done in the circuit ? Thanks.
Hi Issac for 12 volt LA battery the maximum allowed terminal voltage is 14.2 , and the maximum initial current is 25% of the rated capacity. design a constant voltage charger with 14.2 volt regulated supply capable of supplying a maximum current limit of 25Amps. Supply this through a relay contact the relay should be an under voltage relay to open at 10.8 volts. the relay can be 12 volt @ 50 to 100mA coil with a contact rating of 30Amps DC. The UV switching circuit can be with a comparator
IC 741 with a transistor to switch the relay you can use any comparator circuit appeared earlier in Circuitstoday.
I built an inverter of 500w capacity that is using 12VDC/100AH Battery, but Iam faced with the problem of battery overdrain/overcharging. Pls, help me with a battery protection circuit that can disconnect a system at 10.8 and 15.0VDC. Thanks.
Hi Ocsee 10 batteries in series and 1.5AH each. Since you have already regulated 140DC it is just 1 volt higher than the required voltage. only current limiting is required. When battery is discharged fully terminal voltage will be around 10.8, that is 108 volts 140-108 @400mA 32 / 0.4 80 ohms 20 watt resistance is required. or you can use a MOSFET series current limiter for 400mA. Thyristor or triac cannot be used as you have already regulated 140Volt DC.
Hi,
i need to charge 10 batteries connected in series
Battery specs are: 12 Vdc 1.5 Ah
So, to charge 10 batteries connected in series i need 120 Vdc
I have already regulated 140 Vdc.
Can you Help with basic Schematic including Traic control
Thanks
Just wondering if anyone has a charge with dump load circuit for my 24v system.I’m running 2 sets of 8v 4 cell lead acid 170ah batteries linked 3 in series then parralell.Just built an alternator from Fisher&Paykel motor,split the windings into 2 sections for vawt low speed winds.It puts out up to 100v rectified @ 2000rpm 40v @ 100rpm(unsure what amperage).Any help would be greatly apreciated.
Hi Kushlendr first reduce the transformer sec voltage to 15volt RMS AC. without connecting the output to battery set the output voltage to 13.8volts with R4 pot. reduce R5 to 0.5 ohms 2 watts connect to battery and charge it for 12 hrs.
sir, plz tell me how can i charge 12V 7AH lead acid battery..
hey thanks for the reply much appreciated ,could anyone point me somewhere else to meet wot i need to do thanks .
cheers
Hi Stefan for charging 430AH 30V lead acid battery. you require a constant voltage source of 34.5 volts and maximum charging current limited to 30%, that is 130Amps. For boost charging 35.5 volt again limited to 100Amps. This requirement cannot be fulfilled by the above circuit.
gday there everybody was just looking at this circuit and i need to build a charger to charge a 430ah 30volt lead acid battery ,can anybody tell me if this circuit could be adapted to do so and what i would need to change .
thanks
Hi
Can you please give a circuit to charge 4x12v33ah batteries in series? or can I use the above posted circuit in series to charge this battery size ?
Please reply.
dear sirs,
can i used this circuit to charge 2X12 volt 60 AH batteries by using a transformer with 24 volt /10 amp.
pls reply with the modification required
Hi Srinivas sorry for the delay in replying. Change to LM338, transformer to 35 volt 5 amps. Bridge rectifier 7 amps or 6A4 X 4 for the bridge, reduce R5 to 0.125 ohms that is use 4nos 0.5 ohms 5 watts in parallel, Chenge D2 to 6A4 and fuse to 5 amps. since the current pulled by Q1 still low even with 120 ohms for R3 and 5 K for pot, BC547 can be still used 100 ohms is to limit base current during short circuit of the out put leads, i prefer a 470 ohms or 1K so that the base current is limitted to less than 20mA during just a short circuit. you can go ahead. you can send your further queations to my email id seethasub@hotmail.com
Hi every body,
I want to make a charger for 02 nos 12v lead acid batteries in series with each rating of 200AHs. Can any body help me to give a circuit. BAttery are for diesel genset and charger required for standby chargig. Please with detail..
i need a charger to charge a car battery of 12v and 88Ah
Dear Mr. Seetharamanan,
” Greetings from FSMS Pvt. Ltd., Chennai “.
Thank you for the Charger Circuit (shown below) and explanations given. We would like to make a Charger to charge two 12V, 17Ah Lead Acid batteries connected in series.
I think that,
The Transformer 35V/3A to be replaced with “Transformer 35V/5A”.
The 3A bridge rectifier to replaced with “7A bridge”.
Regulator LM317 to be replaced by “LM388”.
BC547(Q1) to be replaced by “2N2955 power transistor”.
100Ω (R1) to be replaced by “6.8 Ω”.
0.85Ω/2W (R2) to be replaced by “0.1 Ω/5W”.
We would request you to provide me the Circuit for “Charger to charge two 12V, 17Ah Lead Acid batteries connected in series (24V, 17Ah)” (with explanation), with features of
o Automatic shutting down of charging voltage, when Battery charge is full, and vice versa.
o Charging indicator, charge-full indicator.
Awaiting for your earliest response.
Thanks and Regards
P. R. Srinivas
Sr. Manager – Technical Support,
BIOMEDICAL ENGG. MAINTENANCE SERVICES (BEMS)
HQ, Faber Sindoori Management Services Pvt. Ltd,
Paras Plaza, 20/31 Cathedral Garden Lane,
Nungambakam, Chennai-600034
Tel: 044-42649403/04 Extn: 120
Fax: 044-42649405
Mob: 095512 69912
from where can i get a good wheelchair driver circuit for 180 W motors
i need a charger circuit for a wheelchair. my amp hr rating is higher(24 V 18Ah) …what modifications should i make in the above circuit ?
Dear Mr.Seetharaman,
This circuit is really nice and i would request if you could send me a circuit diagram showing a RED LED while charging and a green LED when the battery is full. Rest everythng is ok with me.
Thanks in advance.
Cheers/Sathish
Hi Preeti Batteries cannot be charged in parallel as their present charecter will be different so better to charge the lead acid batteries in series. to charge them in parallel you require individual charging circuit for each battery from the charger
can t i charge these batteries in parallel ??
Hi Preeti all the 6 batteries you have charge in series. hence the current will be still 1.3 / 10 = 130mA and a maximum of 400mA. The voltage has to be 13.8 X 6 = 82.8volt.
Hi Seng Siong Lithium batteries require different type of charger with protection etc., this cannot be used.
hello, i want to charge 6 lead acid batteries( each 12v/1.3 amp hour ). what will be the current requirement of the charging circuit? please help me if suitable circuit for charging batteries in parallel configuration is available.
is this circuit compatible with 24V lithium polymer battery pack?
Hi Anthony send your email id to seethasub@hotmail.com i will reply and send you the diagram
Hi Anthony to charge sealed lead acid battery you should have aregulated power supply with 13.6 volts out put and the maximum initial charge current shoild not be greater than 30% of the rated capacity of the battery.
Thanx Seetharaman, next Q. If I go for 2N2955 option, how will the circuit change – can you send me a new diagram? I have read about charging SLA batteries, will this constant current charger decrease the life of SLA batteries-alternatively do you have a circuit to charge 24V 17Ah sealed lead acid battery?
Hi Anthony your idea correct, you have to change the transformer to 5 amp rating with the same voltage ofcourse a 7amp bridge LM388 or same 317 with 2N2955 (PNP power transistor with 6.8 ohms) to increase the current rating. 0.1 ohm 5 watts will do.(0.5 / 0.47 ohms 1 watt 5nos in parellel will also suit)
Hi Seetharaman, If I want to step up to enable me to charge 2x 12V 17Ah batteries in series can I use the same circuit as the 2x13Ah or would I have to change the following:
T1 30-35V 5A transformer, 7A Bridge rectifier, IC LM337 (?)- would I need to go for a 5A Voltage regulator and as I only know of Positive 3 terminal like LM338 I would need to change circuit? Lastly R2 to 0.1 ohm 10W . Alternatively step down to LM317 to drive 2N3055 transistors ?
Hey!
Thanks so much for the circuit, I got it to work great. Just a quick question: What do the capacitors actually do? And how did you come to these values?
Cheers
Hi Seetharaman, This is a great circuit and near perfect for me, thanks.. I read your reply to Farada about switching on and off, but I cant figure out how to do this with your explanation. Is it possible you can draw this for me. I would like to be able to identify when batterys are charged and when they are charging (ie: with 2 LEDs?). So it will switch off and on sutomatically because my charger will be always connected. Also(!) can you protect from draining batterys if charger is switched off?
Thank you, Carl
Hi Dedi 9 volt dry battery or 8 volt lead acid battery or 9.6 volt nicad battery. kindly specify your battery type voltage AH capacity etc.
can i use this circuit for 9 volt battery and what components i must change…
sorry my english isn’t good
Hi DYK this charger cannot used for charging 100 amp batteries. This can be used upto maximum capacity of 20AH.
batteries.
Hi Estephane can you give you battery’s complete detail and whether you want to charge them together or one at a time.
Hi Louie The same charger can be used for charging 24volt 4.5AH battery. reduce R2 to 0.47 ohms 2 watts.
Hi,i would like to ask if you could give me a circuit that can charge a battery of a forklift,a 24volts and a 36volts.
what can i do to make this circuit charge 100AMP batteries?
24 volt 4.5 Ah charger please…
I desire to construct the circuit for an inverter in which can use two car batteries by which one battery to provides the dc input to the inverter and the second battery to be charged at the same time and vice versa without the need of solar power.Please can provide me with a circuit diagram?
Thank you in advance.
Hi for 24 volt 13AH lead acid gel battery the initial charging current (for a flat battery)preferrably sholud be limitted 3.5Amps max. With a regulated power supply of 27.6Volt. can charged for 12hrs to 15hrs max. As the battery terminal voltage increases tofinal level the charging will fall down slowly to trickle level. Hence the resistance value for R2 should be reduced to 0.2 ohms 5watts. Transformer rated at 30 volt 4amps bridge rectifier rated for 5amps and IC as LM337K (T03 casing)
Hi,
R2 is the current “Ah” limiter. There is a detailed discussion about calculation of the R2 in another battery charger circuit in this website.
Thanks
What’s about the base of BC547 if I added it for a charge indicator?
Could I charge a 24v / 13amp battery with this circuit?
Hi D2 is 1N5403. The transformer can be 30 volt AC at 1 Amp as our out put current is limited to less than 1 amp by Q1. As the charge indicator is mandatory you can connect Q2 BC547 similar to Q1 with collector connected through an LED and a 2.7K ohm 1/4 Watt resistance to C1 positive. When the drop across R2 is greater than 0.65volt the LED will start glowing.
pls. how do make the circuit automatic so that when the battery is fully the circuit shuts down and vice -versa.also wiTH indicating LEDS
sir
i have a inverter circuit , but for charging we are using relay and capacitor.so the battery not charge fully, i heard abourt the circuit by using bta 12 triac and lm324 no need of relay and capacitor,can you help me
my requirement is instad of relay i need bta12 for switching for current limitting avoid capacitor
expecting your reply
thank you
vinu.india