These arguments and anecdotal complaints never seem to cover all the details. Temperature of charge and discharge, charge and discharge rates, fidelity to charging and discharging limits...
I am pretty sure you can take new LFP cells and treat them well with out any BMS, and I am pretty sure you can ruin them with a BMS and improper behavior. Not to mention that BMS (at least the cheap small ones appropriate for my little packs) are black boxes and not exactly trustworthy. I think you want to ensure a new pack has all good cells at the start. I am playing with a set of used and abused cells (40Ah TS). I can't predict anything about them, and won't make any broad claims about TS LFP cells based on what I do. I doubt a BMS would keep it running right, so I am opting for bottom balancing and close attention for a while. I plan to be gentle with them, my charge rates are around 1C, will probably try to operate between 20% and 80% SOC. I think most OEM packs are doing this - sacrificing 40% of max charge in favor of few failures- and their longevity is probably directly attributable to this. I don't think bottom balancing is cult-ish. (It IS rude to talk bout it that way.) It is just complicated. There is more to care and feeding of Li cells than just balancing and BMS. Apparently, we can't assume that all the cells we buy are good, so we have to deal with that. We have to be very careful comparing results, because there are so many fault modes, both in operation and in measurement. Blasting all use of Li cells versus PbSO4 is just silly, particularly for smaller applications. No way I am putting 60V of PbSO4 on my trike. On Mon, Apr 21, 2014 at 11:27 AM, damon henry <[email protected]>wrote: > So what BMS are people using with the batteries you are selling and how > much does that add to the cost? With your strong opinions about having to > use a BMS I am surprised you are willing to sell the modules without an > appropriate BMS as part of the deal. Are you providing any warranty or > after sale support? It seems as if you are using lack of BMS and warranty > support as a negative to the Chinese cells, yet wiling to let people walk > right down the same path as long as they buy what you have to offer. > I hope to buy lithium for my truck some day and feel that even with their > flaws the Chinese batteries are at least a known commodity at this time. > Buying raw cells meant for a Leaf or a Volt without the hardware or > firmware they were designed to be used with sounds a little sketchy to me, > if for nothing else, just for the lack of expertise available. I remember > how some of the first people to try the Chinese cells got burned back in > the day :) Now at least there is no lack of opinions about how to use them > properly and plenty of real success stories. > I remember David Nelson bringing his TS cells to my house to work on them > together before he stuffed them into his Gizmo several years ago and I see > that for his application, his cells and approach to maintaining them has > worked out well. > > damon > > > Date: Mon, 21 Apr 2014 05:38:33 -0700 > > From: [email protected] > > To: [email protected] > > Subject: Re: [EVDL] self-discharge of CALB 180Ah LiFePO4 cells > > > > BMS is very important to the life of any Li-ion cells. Is there a > production > > car not using BMS?. Bottom balance W/O BMS is a disaster waiting to come > > true. I didn't mention the difference in costs of cells like CALB and > others > > compared to the NEW (not from wrecks) Leaf cells I sell. How about 48 > > modules = 24kw for $4800? Try to beat that with CALB, etc. > > > > > > > > -- > > View this message in context: > http://electric-vehicle-discussion-list.413529.n4.nabble.com/self-discharge-of-CALB-180Ah-LiFePO4-cells-tp4669067p4669085.html > > Sent from the Electric Vehicle Discussion List mailing list archive at > Nabble.com. > > _______________________________________________ > > 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) > > > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140421/5af5ff54/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) > > -- Put this question to yourself: should I use everyone else to attain happiness, or should I help others gain happiness? *Dalai Lama * Tell me what it is you plan to do With your one wild and precious life? Mary Oliver, "The summer day." To invent, you need a good imagination and a pile of junk. Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html> A public-opinion poll is no substitute for thought. *Warren Buffet* Michael E. Ross (919) 550-2430 Land (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone (919) 631-1451 Cell (919) 513-0418 Desk [email protected] <[email protected]> -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140421/f02ea9a8/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)
