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trying to get 3 amps (from buck converter, battery power)

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dl09

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i connected 2 18650 lithium ion batteries in series, generating 7.4 volts. i connected the batteries to a buck converter. the input is 7.4 volts. the output current is 1.19 amps. the output is connected to a 2 ohm 200 watt resistor. why is the output current not 3 amps? i tried adjusting the constant current potentiometer, that won't work. i tried adjusting the constant voltage potentiometer, that won't work. why is the output current not 3 amps?
 

Re: trying to get 3 amps.

Because the buck converter is not designed to provide 3 amps?

I am sorry for the vague answer, but you must realize that your question is quite vague and is withholding crucial details.

You say you are feeding it to a buck converter...is it something you built or purchased? If so can you provide a diagram, a model number, a datasheet, a link to a website?

You also don't mention what happens, for instance, if you load your setup with a lighter load, i.e a 20 ohm resistor.... can you make the output current vary by varying the voltage setting potentiometer?
 

Re: trying to get 3 amps.

RTFM. the reason you can’t get 3 amps is because your battery is incapable of producing 3 amps.
 

Re: trying to get 3 amps.

schmitt trigger said:
Because the buck converter is not designed to provide 3 amps?

I am sorry for the vague answer, but you must realize that your question is quite vague and is withholding crucial details.

You say you are feeding it to a buck converter...is it something you built or purchased? If so can you provide a diagram, a model number, a datasheet, a link to a website?

You also don't mention what happens, for instance, if you load your setup with a lighter load, i.e a 20 ohm resistor.... can you make the output current vary by varying the voltage setting potentiometer?
Click to expand...

i bought the buck converter at walmart, i did not build it. it has two potentiometers. 1 potentiometer varies the current. i tested it, it works. 1 potentiometer varies the voltage. i tested it, it works. the advertisements say, it has a maximum output current of 10 amps. i tried a 6 ohm resistor, if the input is 11 volts, the output current is 1.5 amps, i think. i haven't tried a different load. any way to make sure the output current is 3 amps?
 

Re: trying to get 3 amps.

Barry brings a very good point, perhaps the batteries can't supply that much current without an excessive voltage drop.

Take an automotive battery and repeat the test. That battery certainly has the capability to provide the required power.
 

Re: trying to get 3 amps.

Can you give a link to the Buck converter...so we can see its full spec?
 

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