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nashspecs • Aug 6, 2008

# Producing high current from batteries

hi 2 all! i still am an undergrad and im working now on my project. im having difficulty on producing high current from mere batteries.

for example...

i want to produce current by about 2 to 3 amps form a 7.2v 2800mAH battery.

i dont know where to find simple circuit just to produce that amount of current. im talking about simplicity because i want it to be as light as possible.
i would be so thankful if someone can help me regarding this matter!!!...
xheavenlyx • Aug 6, 2008
The reasoning is flawed. What do you need the current for? What circuit is it being used in? Because you can produce an Amp or 2 by just shorting the battery leads, but that may explode your battery!

nashspecs • Aug 7, 2008
ah yes im sorry... i would be using that as a supply for my high speed high torque motor.. so u do know how to play with batteries? im so thankful if you can help me regarding this matter... how can i produce that amount of current and at the same time not explode my batteries???
prestonee • Aug 7, 2008
Just wanted to point out you said the battery is 7.2V with a rating of 2800mAH. 2800mAH means 2.8 = current * time, so according to the battery spec when fully charged it could provide 2.8 amps for 1 hour. You can use that equation to determine the max current it can support for the time period your application requires.
Ashraf HZ • Aug 8, 2008
prestonee
Just wanted to point out you said the battery is 7.2V with a rating of 2800mAH. 2800mAH means 2.8 = current * time, so according to the battery spec when fully charged it could provide 2.8 amps for 1 hour. You can use that equation to determine the max current it can support for the time period your application requires.
Perhaps, but you are still limited to the maximum current drain! This can be 50mA, 120mA, etc. For pulses, this may be up to 400mA. Drawing current more than the limit will affect battery performance and may cause some issues.

nash, check the battery datasheet for that specification.

1) Can you tell us the make and model of the battery?

My friend told me about amplifing the current at the expense of voltage. Perhaps this is the circuit you need.

2)Is there a minimum voltage you need to operate the motor?
3)What kind of high torque motor is it? DC? Servo?
hello,well you can do one more thing,you can use a simple op-amp to amplify the current or else,is it possible to make the circuit a little bulky,u can use a transformer instead
reachrkata • Aug 8, 2008
Hi Saurav,

I would disagree to your suggestions - using an opamp would need additional supply which I think our friend doesn't have. Also using a transformer though would increase the current would reduce the voltage also. Nashspecs needs to decide whats the minimum voltage he requires.

Nevertheless, you sure need to check your battery specs. I am pretty confident that getting 2-3A pulses would reduce the battery voltage during the high current pulse.

-Karthik
Ashraf HZ • Aug 9, 2008
Try getting hold of Lithium-Polymer battery packs. They pack a big punch in terms of amperage. Say.. 6A at least? 😀

You can check here for cost effective ones (starting from \$15):
EnerLand Lithium Polymer Battery Packs for Electric Flight from Hobby Lobby!.

I'm pretty sure you can find these stuff at nearby RC hobby stores or electronic component shops. They'll be much cheaper than ordering online from overseas.
nashspecs • Aug 12, 2008
thanks for ur replies.. reachrkata is right, i would not provide another supply for the op amp.. what i only have is the battery with a 7.2v 2800 maH rating.. wat i have is a dc motor and not a servo one.. do you know how to raise the current without the expense of voltage? because the operating voltage of my dc motor is at 7.2v.. and i would be needing it to retain the speed of my motor.. high current is what i need for the torque..

nash, do you have specifications for your battery? Can you tell us more about it? Like, if its Alkaline, NiMH, Lithium Polymer, etc.

The specification of interest would be the Max Continuous Current, or something similar.
barryn56 • Aug 24, 2008
If you only need a high current for a short period (e.g. motor start current) you can use a super capacitor charging/discharging circuit. Nickel Metal Hydride batteries can supply very high currents.
ajmer • Aug 31, 2008
hi crazy folks!!
i 2 want to make the same project.. could u plz mail me its details and specifications.