You have a high resistance connection about 5 or 6 cells from one end of the battery pack. A cell voltage will not read much of a voltage drop when not under load. At a given load you are losing about 20.8 volts. Divide that by the cell voltage and this will be about the number of cells from one end of the pack where the bad connection is.
It the same thing trying to find a bad receptacle in a string of receptacles. When there is no load on this circuit, a receptacle indicator or a volt reading will all read about 120 volts. Now put a load on that circuit and test each receptacle until you read about 120 volts, the last one is the bad one or poor connection. Connect a volt meter leads to the most positive and most negative of the battery. Read the voltage of the pack not under load and then under load which will indicate a voltage drop. Now connect the volt meter across a cell post connection plus the next link attach to the next cell. If you just go across the cell it self, you may not pick up this voltage drop. Reading the voltage across the cell only which reads good, indicates there is a high resistance link connections. To find a high resistance link connection, connect the volt meter lead directly to one cell of the cell post and to the other cell shunting the link. This is call a cell shunt test we use to make sure that a initial installation of the links have a good connection. If you find one connection that has a high resistance, you then can do a shunt test by bridging or shunting each link with a volt meter in the milliamp scale while the charger is on. CAUTION: You must have insulated electrical tools, rubber electrical rated gloves and a electrical rated rubber blanket to cover all the other connections you are working on. I cover many of my tools with heat shrink, which includes the sockets, sockets extensions, and ratchets, After you connect the volt meter, turn on the charger to about 10 amps. Lets say many of the cell links read about 0.001 amp, but when you find one that reads higher than that, then tighten that one connection until it matches the ampere of the other links connection. If you are attach a BMS wire to the cell, it is best to make the connection directly to the cell and the link goes on top otherwise the voltage indication to the BMS may picking up the incorrect reading because of a high resistance reading. I am going to use a plated copper which is bi-metal connection design for this type of connection which is furnish with the BMS units. Roland ----- Original Message ----- From: Sam Shepherd via EV<mailto:ev@lists.evdl.org> To: ev@lists.evdl.org<mailto:ev@lists.evdl.org> Sent: Saturday, September 13, 2014 6:03 PM Subject: [EVDL] Pack voltage Would anyone have ant thoughts as to why my "pack" voltage starting out with 160.8 volts on the dial would drop to 140 volts on a mild "pull"? It has just started doing this. I didck. the cell voltage of each cell with no real diferences. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140913/6cc6bf74/attachment.htm<http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140913/6cc6bf74/attachment.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<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... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140913/2215a8b0/attachment.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)
