Lawrence, For the current you are talking about, assuming 100Ah LiFePO4, you need to go with at least the CALB CA series (the gray ones) of cells. For the same conditions, the TS (Winston) cells sag more than the CALB SE (formerly SkyEnergy Blue) cells, and those sage more than the CA series.
For some good video of a discharge test (on a CA cell) using a spanner wrench to short the terminals check out both https://www.youtube.com/watch?v=xcuyfS7yybQ and https://www.youtube.com/watch?v=lyYfFeWwd9I and I think you will decide that the CA cells might do the job. As for charging, if your K&W can guarantee that it won't charge over a given voltage it will be fine. It really doesn't take a very sophisticated charger to charge LiFePO4 cells. Many of us have found that if there are no unbalanced loads on the pack and the set of cells are good that they just don't drift with respect to each other. If you do install any sort of BMS on part of the pack you will have problems so don't go with a partial BMS. Either install one or don't but make sure you read up from a wide variety of places on the pros and cons of installing an automatic BMS or you being the BMS. What you go with will also be a factor in whether you top balance your pack or bottom balance your pack. Each way has its pros and cons so get educated on the options. I know that some here don't like/agree with Jack Rickard of EVTV.me. Not all scientists liked/agreed with Thomas Edison either. Jack at least posts about and if possible videos his "failures" so all can learn from them. At least read the blogs if you don't have the bandwidth or desire to watch his long videos. Having followed his progress over the years I have learned that it can take several blogs/episodes before you finally get all the pieces supporting why he makes particular claims so don't read just one post and write him off. As for my rig I have a pack of TS cells made in November 2009. They are top balanced because of the limitations of my Zivan charger. I want the charger to follow the charging procedure of charging to 3.6vpc and stopping when the current drops to 0.05C. The Zivan tapers the current to a few mA and stops when the soak charge timer finally times out. As such, I charge my pack to 3.455vpc right now and am planning on dropping that voltage a little bit farther when I get a chance to more accurately test resting voltage after a charge with no load on the pack. I think I still might be overcharging my pack slightly. As for a BMS, I took that off 23 months ago and the pack appears to still be in balance as measured right at the end of charge when the charger is putting out less than 200mA into a 200Ah pack. HTH, On Sat, Jun 8, 2013 at 6:17 PM, Lawrence Rhodes <[email protected]>wrote: > I've checked out some Chinese battery suppliers and seems prices are > around 100 > dollars a cell. A 144v pack will be 45 or so cells. Should yield a 50 > mile > usable range on the Ford Aspire. What is the best supplier and battery > for the > money? Could a regular K&W work as the charger? Trying to do this on the > cheap. What is the best bargain in BMS? I've been into lead so long I need > advice on the best way to go on lithium. The 144v system draws 500 to 700 > amps > max. Lawrence Rhodes > _______________________________________________ > 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) > > -- David D. Nelson http://evalbum.com/1328 http://www.levforum.com Nokia Lumia 920 Windows Phone 8 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20130609/49986cb9/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)
