This design can be used for charging high current lead acid batteries in the order of 100 to 200 AH, the design is perfectly automatic and switches of the power to the battery and also itself, once the battery gets fully charged.
Looking at the figure we can understand the circuit idea through the following simple points:
There are basically three stages in the shown configuration viz: the power supply stage consisting of a transformer and a bridge rectifier network.
A filter capacitor after the bridge network has been ignored for the sake of simplicity, however for better DC output to the battery one can add a 1000uF/25V capacitor across the bridge positive and negative.
The output from the power supply is directly applied to the battery which requires to be charged.
The next stage consists of an opamp 741 IC voltage comparator, which is configured to sense the battery voltage while it is being charged and switch its output at pin #6 with the relevant response.
Pin #3of the IC is rigged with the battery or the supply positive of the circuit via a 10K preset.
The preset is adjusted such that the IC reverts its output at pin #6 when the battery becomes fully charged and reaches about 14 volts which happens to be the transformer voltage at normal conditions.
Pin #2 of the IC is clamped with a fixed reference via a voltage divider network consisting of a 10K resistor and a 6 volt zener diode.
The output from the IC is fed to a relay driver stage where the transistor BC557 forms the main controlling component.
Initially, power to the circuit is initiated by pressing the "start" switch. On doing this, the switch bypasses the contacts of the relay and powers the circuit momentarily.
The IC senses the battery voltage and since it will be low during that stage, the output of the IC responds with a logic low output.
This switches ON the transistor and the relay, the relay instantly latches the power via its relevant contacts such that now even if the "start" switch is released, the circuit remains switched ON and begins charging the connected battery.
Now as the battery charge reaches about 14 volts, the IC senses this and instantly reverts its output to a high logic level.
The transistor BC557 responds to this high pulse and switches OFF the relay which in turn switches of the power to the circuit, breaking the latch.
The circuit gets completely switched OFF until the start button is pressed once again and the connected battery has a charge that's under the set 14 volt mark.
How to set up the circuit.
It's very easy.
Do not connect any battery to the circuit.
Switch ON power by pressing the start button and keep it depressed manually, simultaneously adjust the preset such that the relay just trips or switches OFF at the given rated transformer voltage which should be around 14 volts.
The setting is complete, now connect a semi discharged battery to the shown points in the circuit and press the "start" switch.
Due to the discharged battery, now the voltage to the circuit will drop under 14 volts and the circuit will instantly latch, initiating the procedure as explained in the above section.
High Current 10 to 20 Amp Automatic Lead Acid Battery Circuit Diagram
Looking at the figure we can understand the circuit idea through the following simple points:
There are basically three stages in the shown configuration viz: the power supply stage consisting of a transformer and a bridge rectifier network.
A filter capacitor after the bridge network has been ignored for the sake of simplicity, however for better DC output to the battery one can add a 1000uF/25V capacitor across the bridge positive and negative.
The output from the power supply is directly applied to the battery which requires to be charged.
The next stage consists of an opamp 741 IC voltage comparator, which is configured to sense the battery voltage while it is being charged and switch its output at pin #6 with the relevant response.
Pin #3of the IC is rigged with the battery or the supply positive of the circuit via a 10K preset.
The preset is adjusted such that the IC reverts its output at pin #6 when the battery becomes fully charged and reaches about 14 volts which happens to be the transformer voltage at normal conditions.
Pin #2 of the IC is clamped with a fixed reference via a voltage divider network consisting of a 10K resistor and a 6 volt zener diode.
The output from the IC is fed to a relay driver stage where the transistor BC557 forms the main controlling component.
Initially, power to the circuit is initiated by pressing the "start" switch. On doing this, the switch bypasses the contacts of the relay and powers the circuit momentarily.
The IC senses the battery voltage and since it will be low during that stage, the output of the IC responds with a logic low output.
This switches ON the transistor and the relay, the relay instantly latches the power via its relevant contacts such that now even if the "start" switch is released, the circuit remains switched ON and begins charging the connected battery.
Now as the battery charge reaches about 14 volts, the IC senses this and instantly reverts its output to a high logic level.
The transistor BC557 responds to this high pulse and switches OFF the relay which in turn switches of the power to the circuit, breaking the latch.
The circuit gets completely switched OFF until the start button is pressed once again and the connected battery has a charge that's under the set 14 volt mark.
How to set up the circuit.
It's very easy.
Do not connect any battery to the circuit.
Switch ON power by pressing the start button and keep it depressed manually, simultaneously adjust the preset such that the relay just trips or switches OFF at the given rated transformer voltage which should be around 14 volts.
The setting is complete, now connect a semi discharged battery to the shown points in the circuit and press the "start" switch.
Due to the discharged battery, now the voltage to the circuit will drop under 14 volts and the circuit will instantly latch, initiating the procedure as explained in the above section.
High Current 10 to 20 Amp Automatic Lead Acid Battery Circuit Diagram
wow! this is the simpliest autocharger circuit.
ReplyDeletepls how can i add led to dis circuit
ReplyDeleteYou can connect it across the 100uF capacitor, remember to connect a 1K resistor in series with the LED
DeleteThe relay flickers when reaching the cut off limit, what shall I do?
ReplyDeleteHi Ronald,
DeleteConnect a 100uF...470uF capacitor across the relay coil.
Ok thanks, I'll try...
Deletethe relay keep turning off and on. turn off when reaching the cut off but turns on again after about 2 secs. what shall I do?
ReplyDeleteConnect a discharged battery and then check, and the transformer current must be rated at around 1/10th of the battery AH.
DeleteWithout a discharged battery the circuit will keep fluctuating.
the relay turn off and on. turn off when reaching the cut off but turns on again immediately. what is the solution?
ReplyDeletethe relay turn off and on. turn off when reaching the cut off but turns on again immediately. what should I do?
ReplyDeleteThat shouldn't happen, because the moment the relay trips, it cuts the power supply to entire circuit and also to itself and therefore cannot switch back.
DeleteDid you connect a filter capacitor? Remove it if you have used one.
Also, have you done the connection of the start button as shown in the figure, just check them....
the primary coil trips but the battery is still connected to the circuit, a fraction of the voltage of the battery drops the moment the relay trips, the circuit senses the voltage of the battery again not yet at the cut off, powering the relay again...
DeleteOK got it,
Deleteconnect a diode in between the bridge positive and the battery positive.
Disconnect the transistor emitter from its shown position and connect it to the anode of the above new diode.
I think this should rectify the problem.
Keep the recommended capacitor connected across the relay coil.
Hi!Great to learn for amateurs like me. One thing which u should add to it is the Printed circuit board for your projects. This will be added benefit for people like me.
ReplyDeleteAsif Usman
asif.met16@gmail.com
Hi! Great site for amateurs like me. It will be great help if the printed circuit board is also added with ur projects. Many thanks.
ReplyDeleteAsif Usman
Hi,
DeleteThanks, though designing PCB layouts is a bit time consuming, will surely try to provide them if feasible.
Regards.
There are some simple software that can design PCB like Circuit Wizard or PCB Wizard. Easy to use. Just input Sir Swagatam's diagrams and it will design the pcb. Just make little rearrangement afterwards to make the design neat. Practicing it will enhance your knowledge.
DeleteCheers!
Does removal of filter capacitor affects the charging time?
ReplyDeleteYes, adding a filter would speed up the charging rate a bit.
ReplyDeleteThe circuit for 10 to 20 amps battery charger is not clear and it is too small. Can you please send me an enlarged circuit diagram. It would be most useful.
ReplyDeleteThanks,
Babu
Please click the diagram to enlarge it.
DeleteThanks.
I was wondering about a couple things on this schematic. Is the N/O under the start a switch or relay? Also, the 12v Relay, is it a N/C or N/O and how do you make the connections. I am using ExpressPCB to make the schematic and then transfer it to a pcb for printing. I am unsure about those two items in particular. Any help, preferably detailed and maybe pictures, would be greatly appreciated as I'm still a little bit new to all this. Thanks.
ReplyDeleteThe N/O is for the relay contacts. An SPDT Relay will always come with both the contacts in one package, here we have used an spdt relay, however only N/O has been indicated, the other contact is obviously is the N/C.
DeleteI would rather advise you to first test the circuit over a general purpose PCB and then go for making the final PCB layout.
The circuit shown at the bottom of this article would be perhaps a better option
I was talking about the one at the bottom of the article. It shows the N/0 but then it shows a relay to the left of that with a ground coming out the left side and a diode looping from the left side(ground side) to the input from the transistor (BC 557). So I'm assuming that is the rest of the pin out hookup for the 12v relay after hooking up the N/O pins to the switch circuit? Sorry to ask so many questions but I'm rather new to this.
DeleteOK got it....the box which shows "Relay 12V" is the relay coil, the wires coming from the transistor and the positive goes to the relay coil....where as the symbol at the left of the box are the contacts of the relay with the N/O and the N/C contacts.
DeleteYes the supply needs to go through the relay contact such that the system shuts OFF completely once the battery charges fully and the relay trips.
Actually I was referring to the circuit at the bottom of the following article, I just forgot to paste the link in yesterdays comment:
Deletehttp://homemadecircuitsandschematics.blogspot.in/2012/07/making-simple-smart-automatic-battery.html
hello, this is great, can i use it to my 50amps lead acid battery? If not so where get i 50amps charger cutter diagram. plz help.
ReplyDeleteThanks, yes you may use this circuit for charging 50AH battery, just make sure that the diode connected at the positive of the battery should be rated at 1/10th of the battery AH, means 50/10 = 5amp to 6 amp diode.
Deletehey.....How can i make it fully automatic????.....like i wanna replace that switch so that i dont need to press it for charging....n it should detect BAttery Voltage n automatically start......
ReplyDeleteThe circuit will need to be changed significantly for that, I'll try to produce the modified circuit in the form of a new article soon...
DeleteK.....thanks.....but can u do anything....like modify this...... is there any chances of changing this????
DeleteConnect power directly to transformer, eliminate the switch.
DeleteWire up the N/O contact with the battery to be charged.
Connect a variable resistor of around 470K across pin#6 and the preset center pin. This must be adjusted for setting the low voltage threshold.
That's all.... Now when the circuit is powered with a battery connected, the relay will activate, the battery will start charging charging via N/O of the relay, once it's full, the relay will disconnect and stay in that position until the battery voltage reaches the lower threshold....the cycle will repeat as long as the battery remains connected, charged and used up...
Thank you very much BRO!!!!!!!!!!!!!!!!!!
ReplyDeletecan i use 14-0-14 transformer??
Deletefor 12V battery you may use the 0-14 tap and for 24V you may use the 14-14 tap, but for 24V, the opamp must be replaced with 1/4th LM324 opamp
Deletehey...i connected a discharged battery which had a volrtage of 10Volt....n i used a 14-0-14 transformer....but the relay switches on and off as soon as i connect the battery....
DeleteDid you follow the setting up procedure as given in the article?
Deleteyup.....i did.....
Deletei understood.......there was a mistake in ma setup.....i didnt read the word simultaneously.....so....how can i make it trip off when battery voltage reaches 13.5..Coz i have used a 14Volts transformer...and it gives a output of 15.7Approx.....
DeleteYou will have to use an external 13.5 volt source. Do not connect the battery initially. Connect the 13.5V source across pi#7(+) and pin#4(-) of the IC.
DeleteAdjust the 10K preset such that the relay just activates at this voltage.
Seal the preset with some glue.
The setting is complete, now you can remove the external supply and power the circuit through the attached transformer.
Press the switch only after connecting a discharged battery having 5 to 10 times AH rating than that of the transformer current.
Thanks......i will do that....
Deletebut the relay fluctuates when i do this....
DeleteAdd a 470uF/25V capacitor across the relay coil....
DeleteK....
DeleteWhat type of amplifier is it??...i mean is it inverting,non inverting, Differential??
ReplyDeleteIt's a comparater, not an amplifier....
Deletewhat is kind of diode i"ll use for this and how many ampere.
ReplyDeletewhat is the AH of your battery???
Deletehii Swagatam,
ReplyDeletegood ckt.
actually am looking for a solar charge controller to charge 150 AH 12V battery. solar panel is 12v/225-250W/ and around 15amps current.
so can i use this circuit by replacing the power supply ckt (transformer,brdige ckt and filter capacitor) with the out put of solar panel?
if yes, what are the necessary changes which i have to do? is there any regulator ckt needs to regulate the voltage to the battery from solar panel?. because the out put voltage of the solar panel will vary up to 20V.
one more doubt,what is the value of potentiometer which is connected to 3rd pin of IC 741.
thanking you ,
mahroof
Hi Mahroof,
DeleteThe circuit will work with all types of solar panels provided the max voltage does not exceed 20V (if the IC is 741) and 30V if the IC is 1/4 LM324).
Yes you may connect the panel supply at the input of the bridge.
It's a 10K preset.
thank you.
Deletethe solar panel open ckt voltage(Voc) is more than 20v as per specification.so any voltage regulator ckt i need to use?
if the voltage is below 20V,we don't want to use any voltage regulator for 12v battery? i mean for 12V battery if we charge by 19V, the battery will not damage?
as the voltage comes from solar panel it self 'dc' i need to use bridge ckt again?
thank fully,
mahroof
A voltage regulator will be required for controlling the output voltage to around 14V, so anything above 14V will require a voltage regulator for 12V batteries.
Deletehello sir,
ReplyDeletei have build this circuit but my problem is the switch can i connect the circuit directly to the battery without using the switch or how do i do it.
secondly i connect circuit to 10v dc battery the relay is not energies but immediately wen i connect it to anything 12v dc or above it energies the relay
and am told to charge 12V 200AH battery with 13.5V supply so the relay energies even b4 the battery attain full charge so how do i overcome this problem
becouse normally 12V 200AH reaches i think about 14-14.5V b4 its fully charge
You will have to read the whole article for understanding the operations.
DeleteWithout switch the system will not cut of after the battery is fully charged.
The preset needs to be adjusted for setting the desired cut off voltage level.
this circute use 24 volt battrey .if any chang please help me.
ReplyDeleteuse 24V relay and 24v transformer....
Deletehello Sir,
ReplyDeleteAre the 10k's all a variable resistor?
I want to use it to charge two 12v 200AH batteries connected in parallel.
what if I want to use it for 24v 200AH or 2V 400AH.
Regards
PK
Hello Sammy,
Deleteonly the one which is at pin#3 is the preset, others are fixed resistors.
for 24V replace 741 IC with IC 324.....
hello sir,
DeleteThanks for the reply.
would the circuit be suitable to charge 12v 400AH battery.
I want to charge four 6v 200AH batteries in series parallel, thus two of the 6v 200AH IN series making 12v 200AH.
Two of the 12v 200AH in parallel, thus making total of 12v 400AH. I am using it to connect to an inverter, keeping it connected permanently. Thus charging the batteries when battery discharges and using the batteries when power outages occurs.
Would leaving it connected to the inverter damage the inventer?
Your responses are highly welcome.
Regards
pk
Hello PK,
DeleteYes you can charge them, just make sure the relay contacts are rated accordingly.
This circuit will not initiate automatically, you will have to press the switch for initiating the charging process.
If the battery is connected to the inverter via a cut off relay then it's fine.
Hello,
ReplyDeleteThanka very much for your response.
Regards
pk
Hello,
ReplyDeleteThanks for this circuit I want to understand if I eliminate the switch as u said above how the relay shall be connected.
best regards
Please check out the last circuit in the following article, it should be in this way:
Deletehttp://homemadecircuitsandschematics.blogspot.in/2011/12/how-to-make-simple-low-battery-voltage.html