[RE-wrenches] 4 ways to keep a battery for a long time

[jay]

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 <ray at 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
>> 
>> 
>> 
> 
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