Ken, What you are asking for is not exactly simple - to measure 22 different voltages on a regular basis. If you have one instrument that can read a low voltage accurately, then you would have to multiplex it somehow through the 22 "channels."
That is what a BMS might do, though many bike and scooter BMS do not. I think a good digital multi-meter and a habit of looking at it monthly would be reasonably good protection against a single cell going south. (I have a new Fluke 117 that seems like a good value.) If they are pretty close together you may not have any difficulty for a very long time. I have two packs I have opened up and repackaged so I can do just this cell voltage checking. Here is an album of images showing them opened up. https://picasaweb.google.com/100767276460953028406/OTELF?authuser=0&feat=directlink I repackeged them so I can get in and out of the with out messing them up. I have BMS, but I don't really know how they function, so maybe I can figure out how they work by checking the cells at different points long the way. I have a small data acquisition system NI USB 6008, that I may try to rig up to collect cell voltages, but I will have multiplex somehow myself. It has only 8 analog inputs, and I have 16 cells. So if I wire up relays I can automate the voltage measurement. There are small low voltage relays that are not very expensive, and the 6008 has digital outputs that can run a relay. I have the advantage though of having programmed this sort of equipment for 15 years now. Do you have any special electrical or electronic skills to bring to bear on this? If not then a manual procedure is probably your best bet. If you end up shopping for mor small packs, it would be nice to compare notes. The pack you see I have that is made from LFP laptop batteries is actually very nice, compact and powerful - and pretty cheap. Mike On Wed, Apr 16, 2014 at 6:13 AM, Willie2 <[email protected]> wrote: > On 04/16/2014 01:41 AM, Peakfoto Digital Photo Still n Video wrote: > >> I have a an ev scooter, with 22 lfp cells. I'm using min bms board and >> evpower cell moduals and an aq Cycle anlyist. >> >> BUT it'd be nice to have a some kind of an setable audble alarm , while >> driving if a/any cells get below a set point. so I can know "the end >> getting close " not >> " you better stop NOW!" . >> >> I kinda know about CELL logs , but sound s a alttle messy. I don't need a >> screen on the dash. any reasobale ideas? >> >> The "stop now" alarm (~2.5v?) can be considered "stop now" when it goes > off with little to no current. It can be considered a "you're getting near > the end" alarm when it goes off with moderate current. I think my > experience will scale to your smaller vehicle and smaller pack: I have 48 > 260ah cells that give me ~150 miles. Normal max currents are around 500 > amps. I believe I have my controller set to pull no more than 800 amps. > In warm weather (50+ deg), it does not alarm; down around 30 deg, it might > alarm at 200-300 amps. When I get within about 10 miles of the end, the > alarm will go off at ever decreasing currents. When I think I'm within a > few miles of the end, I will periodically test by demanding more current. > When it alarms at 300 amps, I can guess I have at least 5 miles left. It > is my understanding that these low voltage events under current draw do no > cell damage. > > _______________________________________________ > 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/20140416/54246858/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)
