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.
I think I like the hall-effect torus sensor better. A 50 mV drop at 500 A is 25 wasted watts! (I'm assuming the Hall-effect sensors don't soak up much power. They're far too small to dissipate anywhere near 25 watts.) Jan On 2014-05-14, at 14:00, Peter Gabrielsson wrote: > Because the resistance of copper changes 4% for every 10 degree change in > temperature. > > Manganin, which shunts are made of, barely change at all. Typically it's less > than 0.05% in the normal temperature range and 0% around 30-40C. > Here's a graph http://images.elektroda.net/89_1304228034.png > Copper would be a vertical line on the same scale as that graph. > > So if you want anything more than a rough indicator, a battery link is > woefully inadequate. > > > > > On Wed, May 14, 2014 at 11:11 AM, Jan Steinman via EV <[email protected]> > wrote: > > From: Michael K Johnson via EV <[email protected]> > > > > That AH meter at lightobject looks very interesting. It doesn't say > > what shunt or range of shunts it can use that I can see. > > > > I have a buck converter that I can put on my tractor to power the > > meter, but obviously I'd need to use a shunt to measure current. I > > have a 50mV/500A shunt installed; do you have docs to check whether it > > would work? > > My favourite shunt is the longest battery lead. :-) Why drop any more voltage > than you already are dropping? > > But you need a system that can be calibrated. If your longest lead drops at > least 50 mV, you can put a trimpot across it to bring it down to exactly 50 > mV. I've done this on two different "house battery" systems for campers, and > it worked well. I put an "amp clamp" meter on the cable, together with a > constant load (turning all the lights on in the camper works well), then > trimming the pot until the readings were the same. > > Jan > > > On Wed, May 14, 2014 at 12:21 AM, John Lussmyer via EV > > <[email protected]> wrote: > >> On Tue May 13 21:11:33 PDT 2014 [email protected] said: > >>> Thanks, Denis. > >>> > >>> It looks like a pretty simple display. I'm sorta hoping for something > >>> with more numbers on it. There seem to be a number of units on eBay that > >>> only go to 100 V and 30 A: > >>> http://www.ebay.ca/itm/5-in-1-Digital-Combo-Panel-Meter-DC100V30A-Volt-Amp-kWh-Watt-Working-Time-/181403417248?pt=LH_DefaultDomain_2&hash=item2a3c7c7aa0&_uhb=1 > >>> > >>> but I'm hoping for something more like this that will do 196V and up to > >>> 500 A: > >>> http://www.accuenergy.com/?discography=acudc-240-series > >>> > >>> This unit could display volts, amps, and kWH simultaneously, but I > >>> haven't found a supplier nor even a price! > >> > >> I'm going to try one of these: > >> http://www.lightobject.com/Programmable-Digital-AH-meter-Ideal-for-battery-monitoring-P278.aspx > >> > >> I have it on my desk, but haven't hooked it up to anything yet. > >> > >> > >> -- > >> > >> Try my Sensible Email package! > >> https://sourceforge.net/projects/sensibleemail/ > >> _______________________________________________ > >> 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) > >> > > > > :::: It is only the great men who are truly obscene. If they had notdared to > be obscene, they could never have dared to be great. -- Havelock Ellis > :::: Jan Steinman, EcoReality Co-op :::: > > _______________________________________________ > 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) > > > > > -- > www.electric-lemon.com :::: Script timed out :::: Jan Steinman, EcoReality Co-op :::: _______________________________________________ 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)
