This is why I have my lead cobalt cells or Li Ion pre balance at the factory. Its seems they do that any more unless you double the cost of the cell.
When I received my new Li Ion cells from Nissan, all of them read between 4.0 to 4.01 volt! It was about three weeks before I had them install, So I connected them all in parallel which acted like one big cell at 4.0 volts which kept them equalized. When I was running a military battery shop, we use this same method for the Ni Cad aircraft cells. I am using the Orion BMS which you can see the data from there manual at OrionBMS.com Roland ----- Original Message ----- From: Lee Hart via EV<mailto:[email protected]> To: Electric Vehicle Discussion List<mailto:[email protected]> Sent: Thursday, June 18, 2015 9:46 AM Subject: Re: [EVDL] Bicycle battery David Nelson via EV wrote: > That is a reason I don't use a cell level BMS. With a cell level BMS > like the miniBMS there is a constant drain on the cells running the > BMS boards and it is nearly impossible to make sure that each board > uses the _exact_ same current regardless of voltage in the cell. > Furthermore, boards like the miniBMS expect that you will balance at > the end of every charge and last I saw, that balance voltage was at > 3.6V or so which is over the theoretical 100% SOC level for LiFePO4 > cells which leads to potential overcharging of the cells on every > charge cycle. If you stop charging without the balancing taking place > and/or let the pack sit for extended periods of time then the > different current draw of each board working 24/7 introduces an > imbalance in the SOC of the cells in the pack. Yes, this is a problem in the BMS market. Like quack medicine, it's full of customers worried about a problem that they don't understand very well. So there are marketeers only too happy to throw together some piece of junk that purports to solve it. It doesn't have to actually work -- it only needs to *sound* like it works, to separate the customer from his money. So some BMS work -- and some don't. The bad ones are so bad that they give the whoel BMS market a bad name. I've written about this over and over... check my old posts. It mostly seems to be of no avail, so I won't repeat myself again. Anything I say is overwhelmed by the noise of the internet. -- The greatest pleasure in life is to create something that wasn't there before. -- Roy Spence -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com<http://www.sunrise-ev.com/> _______________________________________________ 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/20150618/cd4318c8/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)
