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Charging a Battery with high ampere rating battery

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ANTI_HACKER

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I have a 12V/3A dry battery. Can I charge it from a vehcile's 12V/8A battery. if yes how can I? I mean would I be connecting simple terminal to terminal? Should I take care of the 8amperes charging a 3ampere battery. kndly tell me how to charge. Thanks
 

No not really the battery will only draw 3 A from the charging battery

This is due to lesser the load lesser the current

And so I think there will be no major issues in it
 

ANTI_HACKER said:
I have a 12V/3A dry battery. Can I charge it from a vehcile's 12V/8A battery. if yes how can I? I mean would I be connecting simple terminal to terminal? Should I take care of the 8amperes charging a 3ampere battery. kndly tell me how to charge. Thanks
Click to expand...

The battery won't be charged. You can't charge a 12V battery with 12V. At least 13.5V is required.
 

I actually have designed a system which will be implemented inside a vehicle and the system will have a backup rechargable battery. The system will run on the vehicle's battery but incase if its disconnected then it will switch over to the backup battery and simlutaneously the backup battery will be charged by the vehicle's battery so kindly tell me how do i do this. I have a complete sketch of how to do it but i want to confim it. Kindly tell me Thanks
 

Then tahmid the Higher current rating means high input power right so why can't it be charged

Or is charging independent of power input and only Voltage of the source
 

How would i charge it using a vehicle's battery or vehicle's generator? any way?
 

You'd first need to think of a way to step up the 12V to around 14V. A simple boost converter could be used. Current requirement isn't too high.
 

Current just tells the duration of charging time needed and nothing else

- - - Updated - - -

Got my head cleared now
 

jeffrey samuel said:
Then tahmid the Higher current rating means high input power right so why can't it be charged

Or is charging independent of power input and only Voltage of the source
Click to expand...

It depends on the charging voltage, provided the voltage doesn't drop under load. If it does, then charging won't happen.
 
How would I stepup to 14V? I mean how to use a boost converter? Any specific way to do this keeping in mind a vehicle's battery
Thanks in Advance!
 

Thanks! I went through them I got the idea but I am not finding any specific circuit regarding my case. Do you have any link of such design?
 

One more thing: the EMF of the vehicle battery may vary all the way up to 14.4V. So, I think a buck-boost converter should be used instead of just boost converter.
 

You can try this simple charge pump circuit, which allows to charge 12V from 12V in pulses of around 900mA (circuit increase input voltage in power pulses of and :

12V Battery Charger from 12V.jpeg

As replacement for 1N4004(7) (1A) choose P600M SI-D, 1000V, 6A/400Ap, P600.
For BD679 you can choose BD681.

For normal and regular charging you need at least 13,5V, but you didnt specify what battery chemistry you have you just say "dry". Some types needed 14,2V for full charge.

You mention some venhicle, does this "venhicle" have alternator or dynamo to charge main battery ? If alternator is present, I think you have it, he produce 14,2V-14,4V on alternator output or 13,8V on battery terminal point, this can ensure full charging, just limit charging current, look battery datasheet for charging current, I think its around 0,4A-0,6A.
 

Keep in mind the voltage variation of the battery from <12V to >14V. Thus a converter must be used whose output can charge the battery, but will not overcharge or damage it.
 

I want to charge my battery 12V/2.3AH from a vehicle's(car/motor)battery which is a 12v but 8amperes or a little higher/lower(i guess).
what should be the circuit? I might use a voltage booster(step up) but how? Can anyone tell me a specific circuit which i can use to charge my battery having same voltage but just different current ratings. Kindly help me with the exact circuit
THANKS IN ADVANCE!
 

YES i noticed! but it says "i think" and "you can". With respect, I want a specific circuit that would need my demnad. I have told the specs of my charging circuit. It would be good if I find some specific circuit. I googled a lot but i am not any specific circuit. Kindly help
 

Refer the whole thread Cos already we have said that with out having more voltage We can not charge a battery

ie a 12 V battery cannot be charged with a 12 V battery source independant of the current rating

You need to step the voltage up and this needs more circuits here
 

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