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Re: [EVDL] Battery & motor shunts

If he has the 500A/50mv shunt on the battery side and the 1000A/100mv
shunt on the motor side, they should both correctly drive a meter
appropriate for either one. But he should go with the 1000A meter. At
250 amps both shunts should read 25mv. At 500 amps both shunts should
read 50mv. And there's no mental doubling of the values.

If he has a 500A/50mv meter and you hook a 1000A/100mv shunt to it, it
will over drive the meter, not show half values. Readings below 500
amps should be correct. But a 1000A/100mv meter will show the right
current for both shunts.

IIRC, shunts may be affected by heat. I'd make sure you have some
airflow over them if you are using them near their max for any length
of time.

DAC

David Nelson <[email protected]> wrote:
> A friend of mine is converting a Dodge Neon using a Warp9, Syncromotive 700A
> controller, and LiFePO4 batteries. I was recommending to him that he have a
> battery current shunt and motor current shunt. I believe he will be limiting
> battery current to around 300A. He already has a 500A 50mV shunt. I was
> suggesting that he go with a 1000A 100mA shunt in the motor loop so that he
> can use the same analog 500A gauge with a toggle switch. The reason I was
> suggesting the 1000A 100mA shunt is that the meter should still read 500A at
> 500 motor amps but that the 1000A shunt can better handle the short spikes
> up into the 700A range where as the 500A shunt might not do so well. I'm
> trying to avoid the driver having to do a mental doubling of the meter
> reading when on the motor shunt.
>
> Will this work as expected?
>
> --
> David D. Nelson
> http://evalbum.com/1328
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