Re: eBike DC current measure

["Jim Dempsey" <dempsey@oz.net>]

"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 ...."

No bug at all.  I got readings of as high as 120+ amps going unassisted up
hills.  The 120 number would flash, then drop as the bike picked up speed and
the RPMs revved up to that "sweet spot" Lee Hart described.  As long as you
don't run *continuously* at this amperage, you shouldn't have many problems.  I
don't (I have the same unit).

On the flats, the 40-50 amp range was the case unassisted, right in line with
the specs.

Personally, the only times I get frustrated are when the battery gets low.  The
overheat protection mechanism in the relays kicks in more easily, and I have to
actually pedal for a few minutes.  I assume that the lower voltage in the
battery forces the motors to draw more amps to find that sweet spot, and the
increased amperage heats the protection unit more quickly.  Let it cool,
though, and use it sparingly, and all seems well.

I too would love to find an inexpensive and unobtrusive amp meter to mount to
the bars, just for something to play with during the ride.  One can never have
too much data.

Jim Dempsey