18Ah BP17-12
On Tue, Apr 29, 2014 at 2:27 PM, Lee Hart <leeah...@earthlink.net> wrote: > Michael Ross wrote: > >> my power supply allows me to tell it a peak current and peak voltage... >> >> It sounds like I can safely set the voltage to 28.8V and 4 amps, and >> not be concerned if I forget for a few days. Do I have that right? >> > > What is the amphour capacity of your batteries? 28.2v and 4a is OK for > maybe a day, but not for days. At 28.2v, plug the power supply into a timer > and set it to shut off in 16 hours or so. > > If you have to leave it on for days, set the voltage for no more than > 27.4v (13.7v per 12v battery). That is a relatively safe long-term voltage. > > > If I am in a hurry, I could wait for 28.8V, then perhaps set it a 30V and >> 1Amp? >> > > 30v and 1 amp max is OK for an hour or two at the most. That will equalize > the batteries. > > It all depends on how much babysitting you want to do. Probably the > simplest way is to get one of those 12-hour timers that install in a light > switch box, normally used to control a bathroom fan or outdoor yard light. > For example, an Intermatic FF12HC etc. > > http://www.intermatic.com/Products/Timers/InWallTimers/ > Springwound_Auto-Off_Timers/FFCommercialSeries/FF12HC.aspx > > To charge: > - Plug your power supply into the timer. > - Set the timer for 12 hours. > - Set the power supply for 28.8v and its maximum current. > - Wait for it to shut off. The batteries are approximately 100% SOC. > > To equalize: > - Charge as above. Then... > - Set the timer for 1 hour. > - Set the power supply for 30v and a maximum current of 2% of the > battery's amphour rating (i.e. 0.4 amps for 20 amphour batteries). > - Wait for it to shut off. > > > I could rig up a JLD 612 temperature controller to be a minder and shut >> off >> the charge at 100F or so. >> > > When a sealed battery gasses, it heats up and pressurizes the case. If it > charges too long, or at too high a current, it blows the vents open, and > loses water. That's bad for life. > > The heat also shortens the battery's life. As temperature rises, the > battery voltage falls. This makes it draw more current, which causes more > heating... This is called "thermal runaway", and leads to destroying the > battery. A good charger has temperature compensation to detect the > temperature rise, and turn down the voltage or shuts off to prevent this. > > > I could also mange it for temperature and use a plain old 10A 12V charger >> with the cell paralleled. Does this idea have merit/ >> > > If that "plain old 12v charger" is any good. Many of them are nothing but > a transformer and rectifier in a box. No voltage, current, or time control > at all. > > -- > If we knew what we were doing, it wouldn't be called research, would it? > -- Albert Einstein > -- > 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 michael.e.r...@gmail.com <michael.e.r...@gmail.com> -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140429/1e02a239/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)
