Re: (ET) E12M pulling high(ish) current

["David Roden (Akron OH USA)" <roden ald net>]

From:                   Bruce E Conner <BConnor nefn com>

> So what could be causing the higher current draw?  Bad/short brushes?  
> Bad
> battery pack (it's marginal, but OK)?  Wiring of some sort?  Bad shunt? 

Make sure the brake isn't dragging.  You should be able to push the 
tractor easily in neutral.

Check the field connections.  With the motor running in neutral and the 
speed control in full on position (on an E12, which I think has no field 
weakening), you should read full battery voltage across the field 
terminals at the motor.  Excessively low field voltage will cause high 
current draw and low torque.

You may want to try a known-good ammeter and shunt to verify the accuracy 
of your ET's ammeter.  An automotive ammeter might do if used carefully, 
though its accuracy is suspect too.

If I recall correctly, the ET's "shunt" is nothing more than a hunk of 
wire.  Corrosion or loose connections on the connections of this wire 
could cause high resistance in it, thus a falsely high ammeter reading.


David Roden - Akron, Ohio, USA
1991 Solectria Force 144vac
1991 Ford Escort Green/EV 128vdc
1979 General Engines ElectroPed 24vdc
1974 Honda Civic EV 96vdc
1970 GE Elec-trak 36vdc