Hi How do you know if some cells go down way to low?
and how to prevent that any slightly weaker cells to go ..a reverse situation at very high loads, or when it is -40` outside or so and the pack might not be perfectly and evenly heated up yet? I guess the answer to the first line will be the reason of doing bottom balance, all might reach "low" at the same time, and to me THAT argument make at least some sense, (if all of them can deliver the same current in all temperatures and the same SOC(Ah left in cells.) ) Bottom balancers: How do you guys do fast charge? or regen hard with full pack, or handle a cold pack, regen if it is at freezing degree, or maybe less capacity cells in a pack and so on without damaging the cell, if just one or a few was close to full before the others and you regen hard in a cold pack. I dont like that, It WILL happen to me sometime in the future,, if I dont have the system to protect the cells from that overcurrent-situations. How else to KNOW when it happens and how to protect the pack by decreasing the charger or throttle, by manual or by a BMS, if you dont have any kind of per-cell-measurements? Sorry, I just dont get how you do that part. I have also used cells without bms, BUT only 4s, and to 14.40V charger, if more than 4s I dont recomend it. Also,,when I see the fast rate things do change in the very end of a charge or discharge cycle.. It is just not practical to do anything "manual" there if you have a lot of individual and slightly different cells in series. I get that you MIGHT not need cell-balancers at all, or maybe not big ones capable of many Amps in all normal charging (if the cells are ok, and new, and matched production units, and so on) but without any measuring at cell level, how can you say you know anything about that individual cells situation in driving/charging/regen? /John ---------------------------------------- > Date: Tue, 22 Apr 2014 10:43:54 +0100 > From: [email protected] > To: [email protected] > Subject: Re: [EVDL] self-discharge of CALB 180Ah LiFePO4 cells > > My experience differs. I have CALB 180AH blue cells in my car, which has > covered more than 50,000 miles in about 4 years. I haven't looked at the > pack once since installing it. I had a self-built BMS monitoring the pack > to start with, but it got water damaged and I never got around to fixing > it, so for the last 2 years the pack has looked after itself (effectively > it's been "top balanced"). > > > On Mon, Apr 21, 2014 at 12:05 AM, Cruisin <[email protected]> wrote: > >> After selling CALB cells for over 5 years and using them in my own >> conversion, I can tell you from experience the following. At least 15% of >> the cells will change so much in the first year the BMS will react to your >> disadvantage of early charging termination and early over discharging. A >> one >> year warranty that is promised is hocus. the second year will experience a >> 10% failure with no warning of a cell. This makes your car unusable. >> Further >> experience with other Chinese cells is no better, or worse. I now sell and >> use the Nissan Leaf module that is half the price and so far no failures >> like the CALB. I would not ever recommend a CALB cell to any customer. >> Those >> that are pushing the cells like EVTV have inventory they want to unload >> before their is no more demand for Chinese cells. My customers who have >> converted to the Volt and Leaf cells, made by the same S Korean >> manufacturer, are really happier with the results. No more stagnant at rest >> loses that you have experienced. Look at what cells are used in the popular >> plugin cars that are required to provide a 8 year warranty in California, >> no >> Phosphate. CALB would be out of business if required to provide a 8 year >> warranty. They don't even recognize their one year warranty. You wonder why >> you are having problems, wake up and smell the coffee. >> >> >> >> -- >> View this message in context: >> http://electric-vehicle-discussion-list.413529.n4.nabble.com/self-discharge-of-CALB-180Ah-LiFePO4-cells-tp4669067p4669069.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/20140422/72edaa01/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) > _______________________________________________ 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)
