Jan Steinman via EV wrote:
Thanks for bringing that to my attention, Peter, although ±4% for 90% of the typical annual temperature change here isn't TOO bad! I'm guessing temperature affects on battery capacity are of a similar magnitude.
Keep in mind that the wire also heats up from the current flowing in it. That causes additional errors.
There are meters that use copper wire as the shunt; but they include a thermistor that senses the wire temperature, and corrects the current reading accordingly.
I think I like the hall-effect torus sensor better.
Hall effect sensors can be very good; but they too have their sources of error. A classic problem with hall effect sensors is zero drift. (not reading 0 at zero amps).
Simply measuring current isn't too bad. The real challenge is to measure amphours. Any zero offset causes errors to accumulate. An offset error of 0.1 amps on a 500 amp sensor (0.02%, or 1 part in 5,000) accumulates an error of 2.4 amphours per day.
-- Anyone can make the simple complicated. Creativity is making the complicated simple. -- Charles Mingus -- Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.htm _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
