I don't use manganin battery leads (no one does), but I like a temperature-stable reference, and 10-15mV drop in normal operation is noise. ☺ And my longest battery lead is in the middle of my pack so it's biased by half the pack, which would mean that it would be more of a pain to measure since they wouldn't be common. Finally, my battery leads are 2x4ga (equivalent to 1ga) so they don't drop much.
In any case, I already installed a shunt in the original build because I knew I wanted one. I just haven't bought a meter yet. I had been thinking of op amps and beaglebone black, but so far the only thing I've connected to the shunt has been my good voltmeter (which has enough accuracy and precision for the measurement to be meaningful). On Wed, May 14, 2014 at 2:11 PM, 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) > _______________________________________________ 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)
