I do not do it that way. Measure the ampere by shunting the battery link between two batteries. Attach the test leads only to the battery post, not to the battery link.
CAUTION! To do this test, you must used insulated tools, a electrical rated rubber blanket to cover all the batteries not being tested, electrical rated rubber gloves, electrical rated floor mat, and more electrical rated rubber blanket to cover all the metal of the EV. Remove all metal products from your body. I use a 1/8 inch neoprene rubber sheets and heat shrink to cover the tools you are using and the floor. With the charger disconnected from the batteries, use a torque wrench to torque one or two battery links as to the specific torque value by the manufacturer. Attach a milliamp meter shunting that one link that was torque. Turn on the battery charger to 10 amps. Lets say that the link reads 0.01 ampere. While the charger is on, test the next link and lets say it reads 0.02 ampere. Tighten the bolt connections until you read 0.01 again. Do the same to all other links. When all the link shunt current read about the same, then you have a balance link current. If all the cells or batteries read about the same voltage, the resistance will be about the same. Roland ----- Original Message ----- From: Peri Hartman via EV<mailto:[email protected]> To: Electric Vehicle Discussion List<mailto:[email protected]> Sent: Tuesday, August 19, 2014 10:25 AM Subject: Re: [EVDL] CALB bolt terminals getting hot - Question on how to measure resistance. If you use an ohm meter to measure resistance, I presume it is using a 1mA or smaller current. In electronics applications, that's probably fine. But in a situation where typical current is in the hundreds of amps, will taking a measurement that way be reliable? It seems that for low current, you will be measuring more-or-less the best path through the circuit - in this case from terminal to cable. That is, there may be small areas with good metal contact and lots of areas with lesser contact or none. With high current, won't those good contact areas become overloaded and their resistance increase? If so, then I presume a better way to measure resistance under high current would be exactly that: apply high current and measure the voltage drop. Anyone care to validate or invalidate this? Peri ------ Original Message ------ From: "Cor van de Water via EV" <[email protected]<mailto:[email protected]>> To: "Electric Vehicle Discussion List" <[email protected]<mailto:[email protected]>> Sent: 19-Aug-14 9:15:36 AM Subject: Re: [EVDL] CALB bolt terminals getting hot - >Martin, >Delivering 300A at 120V is 36,000 Watts, so losing 350W in the wiring >and terminal connections means only 1% loss in the grand scheme of >things. >A single traffic light turning red in front of you so you have to stop >and again accelerate up to speed is likely a bigger difference in the >efficiency of a trip... > >Cor van de Water >Chief Scientist >Proxim Wireless Corporation http://www.proxim.com<http://www.proxim.com/> >Email: [email protected]<mailto:[email protected]> Private: http://www.cvandewater.info<http://www.cvandewater.info/> >Skype: cor_van_de_water Tel: +1 408 383 7626 > > >-----Original Message----- >From: EV [mailto:[email protected]] On Behalf Of Lee Hart via >EV >Sent: Tuesday, August 19, 2014 9:08 AM >To: Martin WINLOW; Electric Vehicle Discussion List >Subject: Re: [EVDL] CALB bolt terminals getting hot - > >Cor van de Water via EV wrote: >>> Depends on your current. Typically I would say in the order of >>> magnitude of 0.1 mOhm (milliOhm) because a 300A current will then >>> give 30mV drop, which produces 300A x 0.03V = 9 Watt of power loss >>> as heat. > >Martin WINLOW via EV wrote: >> At EVERY connection? In a 120V lithium pack that 's 38 x 9 = >> nearly 350W of heat! > >No; Cor has it right. And, 0.1 milliohms is a *good* connection. You >will discover that it is damnably difficult to make a connection that >good with aluminum terminals! > >-- >You never change things by fighting the existing reality. To change >something, build a new model that makes the existing model obsolete. > -- R. Buckminster Fuller >-- >Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.htm<http://www.sunrise-ev.com/LeesEVs.htm> >_______________________________________________ >UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub<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<http://groups.yahoo.com/group/NEDRA>) > >_______________________________________________ >UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub<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<http://groups.yahoo.com/group/NEDRA>) > > > _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub<http://www.evdl.org/help/index.html#usub> http://lists.evdl.org/listinfo.cgi/ev-evdl.org<http://lists.evdl.org/listinfo.cgi/ev-evdl.org> For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA<http://groups.yahoo.com/group/NEDRA>) -------------- next part -------------- An HTML attachment was scrubbed... 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