RE: eBike DC current measure

[Rivoir Robert <rri@ubp.ch>]

Hello,

Thank you for your reply.

I have purchased a 60 Amp - 60 mV shunt. I measure the voltage with a 20'000
points digital voltmeter.

The result is surprising.

My ZAP DX (dual Revcor motor) consumes 50 Amp with the shaft blocked by the
rear brake (low speed, motors in series) and 110 Amp (high speed, motors in
parallel). The battery voltage falls from 13V to 10V at this load.

Why these values are so high ?. The ZAP system is rated for 400 Watts. Under
10 V it seems me that it would have to consume 40 Amp maximum (or 20 Amp in
low speed)

Where is the bug ? I understand why my 20 Amp / hour battery deads so
rapidly ....

Regards
Robert RIVOIR

	

	> I seek a method to measure the electrical current absorbed by the
motor of
	> my ZAP eBike.
	> 
	> It is necessary to measure 50 amp maximum under 12 V.


	If you need better accuracy, buy a 50 amp meter shunt from an 
	electronics house or from an EV parts vendor like Electro
Automotive, 
	KTA, Wilde EVolutions or such.  Connect that in series with the 
	battery as above, and connect a 50 mv full scale meter (or
multimeter) 
	to it.  Each mv on the meter scale will be 1 amp, and full scale
will be 
	50 amps. 

	You can also use a 500 amp shunt.  In this case, each mv division on

	a 50 mv full scale meter will be 10 amps.  With a 500 amp shunt you 
	might rather use a more sensitive meter, like 5 mv full scale, to
get 
	better resolution, so full scale would be 50 amps again.

	Hope this helps.

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	     David Roden          THE VIRTUAL PD         roden@ald.net
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As mentioned in other posts, you can also use a shunt (which is a precision
resistor designed for current measurements). Most shunts have a standardized
50mV drop at rated current. That's only 0.4% of loss in your 12v. Then the
problem is to find a meter that reads full scale at 50 mV (easy for analog
meters; hard for digital).
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