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Amp Meter

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New Member
Does anyone know how to find the amps an automotive battery is putting out with a 10amp meter. How does an amp meter for alternators work? I'd use one of those but the amps this battery puts out would blow that. I need to figure out the output of the battery so any help would be great.


New Member
the battery will be earthed to the chassis via a thick cable. just measure the volt drop across it.

use the 10A meter to calibrate it, with a light load, like lights.


Well-Known Member
Large currents are measured with a shunt. The shunt is nothing but a low value resistor but it has extras of having little change over temperature and able to dissipate whatever power it must handle.

When I was in high school I made a surprisingly accurate shunt for measuring car alternator output by looking up the resistance per unit length of solid copper wire. In my case I used #8 solid house wire to make the shunt which was 10 milliohms. Coiled it up to make compact.

Remember to put you volt meter at the reference length points. Do not connect the volt meter to the high current terminals which may have some resistance that will make measurement inaccurate.
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