My packs are 16 (or possibly 17) cells of LFP. My highest charge voltage is 60VDC, so a half pack would be OK - always below 30V. CMOS logic and handle that which is convenient.
Should be interesting. On Fri, Apr 18, 2014 at 1:31 PM, Lee Hart <[email protected]> wrote: > Michael Ross wrote: > >> I will probably be implementing a DC battery system for lighting and so on >> so I can get op amp power from there. >> > > I don't know about your lighting system, but in an EV, the pack is > isolated from ground. The voltages you want to measure are "floating" and > not ground referenced. You can't power the comparators from a grounded 12v > system. You either needed a 12v DC/DC converter with isolated output, or a > HVDC-to-low voltage power supply to power the comparators. > > > Or there is already a converter to >> 12V on it. I would not use TTL if I can get around it - because it is >> noise vulnerable. I would likely resort to some optos if noise gets >> difficult. >> > > From a "do this task" POV, an op amp comparator is exactly the right >> function. >> > > Technically, the function needed is a window comparator. This uses two > comparators. One detects a voltage above the reference, and the other > detects a voltage below the reference. But you can get two (or more) > comparators inside a single chip (LM393 for example). > > However, IC comparators are intended for voltages under 30 volts. It takes > a lot of parts to use them to compare higher voltages. > > If the difference between the two halves is too great then it warns. >> if the difference is intermittent then the indication stops. I think >> I may like this better than a slowly increasing brightness >> > > If you want a hard "digital" on/off indication, use the LED in an > optocoupler in place of the red LED in the Batt-Bridge. Use the output of > the optocoupler to switch some "digital" device, like logic gate or relay. > Or, there are optocoupler with built-in hard-switching digital outputs that > could directly switch something on/off. > > But in any case... start by precisely defining the problem you wish to > solve *without* assuming a solution. Exactly what must the output do? Work > backwards from there. > > -- > 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/20140418/306305a4/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)
