The idea of the batt-bridge is that the votlage divider creates a reference for the votlage that the pack tap should have. If you have am even number of cells, it is natural to have the tap in the center and use two equal resistors to create the half-pack reference. However, it is not required and also not possible if you have an odd nr of series cells. Say you have 33 cells. You can tap at the junction between cell 16 and 17 so the voltage is 16/33 of the total pack. Now you just need to use two ressitors in the divider that also give you the 16/33 pack voltage. That would be (for example) a 16k and a 17k resistor. Those values are not available, but you get the idea - it is the *ratio* between the two resistors that counts to give you the correct reference. You could construct the divider from two 15k resistors with a 1k2 and a 2k2 resistor in series to approach the 16k and the 17k value. Hope this gives an idea.
Cor van de Water Chief Scientist Proxim Wireless Corporation http://www.proxim.com Email: [email protected] Private: http://www.cvandewater.info Skype: cor_van_de_water Tel: +1 408 383 7626 -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Michael Ross Sent: Thursday, April 24, 2014 12:30 PM To: Electric Vehicle Discussion List Subject: Re: [EVDL] on the road voltage alarm I think you could test each as half plus the one. The same one. On Thu, Apr 24, 2014 at 3:26 PM, Rick Beebe <[email protected]> wrote: > On 04/17/2014 07:50 PM, Lee Hart wrote: > > 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 > > > > Any ideas for an odd number of cells? Other than adding an additional > cell, of course. > > --Rick > _______________________________________________ > 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/20140424/de61 b69c/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)
