HI Ray, yep agreed, the brain power is going towards Lithium. Thats what I would do.
Schneider also has a high temp shut down. Not sure about OB, or magnum. cheers, jay > On Dec 17, 2015, at 10:55 AM, Ray Walters <r...@solarray.com> wrote: > > Hi Larry and Jay; > > I totally agree, that taking into account charge and discharge rates, DOD, > and temperature, we should be able to more accurately model a battery's > lifespan. We already have temp sensors at the battery, so it seems just a > matter of software to do this. Also battery's nonlinear behavior is well > known and easily modeled. > > This is a huge issue with modeling software like HOMER, as well. I tried to > bring this discrepancy to HOMER staff's attention, and they said I needed to > purchase their consulting package on top of the $400/ yr software license. > Such arrogance is really just ignorance: to not model battery temperature? I > was told that they assumed all battery banks would be in temperature stable > rooms. (Boy, that's a Unicorn assumption, made by engineers that probably > have never even seen an off grid system) > I have systems in Wyoming at 20 below, and others in Haiti's sweltering heat, > but according to all known software modeling and metering, the 2 systems' > batteries are identical. In reality of course, one is going to freeze and > crack the cells, while the other is going to boil over and die an early death > from heat exhaustion. Neither outcome apparently is predictable, except by us > grey haired old know nothings. (I too have a degree in Engineering, and it > took almost 10 years of hard off grid experience to overcome the brain > washing) > > At least Midnite has included a high temperature disconnect for the > batteries, which is a great idea. Most batteries do not want to go over > 105F, and halting charging till the temp comes down will definitely save some > batteries. I just had a large forklift set that stayed on an uncontrolled > charger too long. The entire pack was at 110F and it took several hours to > cool down below 100F. Room temp was 75F. > Its also very possible to predict a battery's freeze point, and disconnect > the load based on voltage, SOC, AND temperature. > > I think everyone is afraid to throw too much brain power at modeling lead > acid batteries that may become obsolete, but as far as I can tell, every > other storage chemistry has similar characteristics: lower capacity at low > temps, a high temp limit, non-linear cycle life depending on DOD, Puekert's > exponent relating capacity vs charge/ discharge rates, volt drop under hard > discharge, etc. > > R.Ray Walters > CTO, Solarray, Inc > Nabcep Certified PV Installer, > Licensed Master Electrician > Solar Design Engineer > 303 505-8760 > > On 12/17/2015 8:26 AM, Starlight Solar Power Systems wrote: >> Jay, >> >> But that data does not consider the non-linearity of the DoD/Cycle life >> relationship. One grossly neglected item in battery monitors is the >> tracking of operating temperature. >> By daily monitoring and logging temperature and DoD and charge rate and kWh >> removed and EQ cycles, days deficit charged, and, and... we should be able >> to model accurate end of life for any battery. >> >> Larry Crutcher >> Starlight Solar Power Systems >> >> >> > > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: RE-wrenches@lists.re-wrenches.org > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org
