EBikes and such often (always?) have a pack assembled with an interface-less BMS. The low warning is it shuts off.
This is not great if you have low capacity cell and it is top balanced. The only way to spot that is to check each cell, often, then you may have an inkling which cells is vulnerable. Bottom balancing does obviate the need to worry about this somewhat, though you still want to find your lowest capacity cell and stop charging soon enough to pamper that one. But cutting off below 3.5V x number of cells ought to do pretty well I think. (for LFP chemistry) That's what one of my charge/BMS does. The other goes to 3.75V. I like an extra cell for that one. Lee, I really like your website which I had not seen before. Thanks for doing that. I hope you get payback from it. How much use would a Batt-Bridge that is adjustable be? As in set the allowable difference between pack halves that send the warning? I don't instantly see where any hysteresis comes from. Is it the difference in drop between the green and red LEDs? Are there any disadvantages to the Batt Bridge? On Thu, Apr 17, 2014 at 7:50 PM, Lee Hart <[email protected]> wrote: > 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? >> > > If you already have a BMS, doesn't it have an undervoltage alarm? > > You don't *have* to monitor every cell to know if one is undervoltage. If > you want something very cheap and simple, try my Batt-Bridge. It splits the > pack into two halves, and compares the voltage of each half. If they are > different, some cell has just went dead, and is at a lower voltage. > > The Batt-Bridge normally lights an LED. But you can use the LED of an > optocoupler, and have the output of the optocoupler turn on a buzzer or > other more noticeable indicator. > > The Batt-Bridge is described more fully at: > http://www.sunrise-ev.com/LeesEVs.htm#battbridge > > -- > If you're not stubborn, you'll give up on experiments too soon. > And if you're not flexible, you'll pound your head against the wall > and you won't see a different solution to a problem you're trying > to solve. -- Jeff Bezos > -- > Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.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/20140417/43cebd3a/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)
