What is the optimal SOC range for cycling AGM batteries

mtdoc

Re: What is the optimal SOC range for cycling AGM batteries

vtmaps wrote: »

mtdoc, AGMs do suffer from stratification issues. Please look at the third post in this thread, and if you click on the first link you will see one of your previous postings in which you knew that AGMs have stratification issues.

--vtMaps

I never said they don't have any stratification issues - just not to the same degree as SLA (please reread the quote you posted - sorry if I wasn't clearer) I have speculated whether it would be worth the effort to rotate the position of my AGMs once a year...

If someone can explain why AGMs would be just as susceptible as SLAs- I'm all ears...

Cariboocoot

Re: What is the optimal SOC range for cycling AGM batteries

mtdoc wrote: »

If someone can explain why AGMs would be just as susceptible as SLAs- I'm all ears...

They're not. Don't worry about it.

vtmaps

Re: What is the optimal SOC range for cycling AGM batteries

mtdoc wrote: »

If someone can explain why AGMs would be just as susceptible as SLAs- I'm all ears...

The paper I referenced in the third post goes into great detail... the pores in the glass mat are large enough for bulk flow of electrolyte. I suspect that AGM batteries do not stratify as easily as flooded batteries, but with flooded batteries it is easier to reverse the stratification with each charge cycle.

--vtMaps

PNjunction

Re: What is the optimal SOC range for cycling AGM batteries

tons001 wrote: »

Will the meter do anything above a 12v battery? My bank is 24v.

The meter is only rated for 12v nominal batteries. The good thing is that I can completely ignore the CCA setting, and immediately proceed to testing the internal resistance. I tried to fool it by purposely setting the CCA to high and low extremes and the resistance measurements stayed the same. It was reassuring to see that my nearly new Optimas and Exides were anywhere from 2.8 to 3.1mohm fully charged.

Onwards ... as for Enersys documentation for us battery geeks, here we go:
http://www.enersys-emea.com/reserve/downloadarea/download.asp?lang=e

I pay attention mostly to the owners manuals, and cross reference that with the application manuals. The brochures I leave to salesman.

When I try to distill it all down to something I can deal with on a general level, be it a pure-lead type, or some other agm that is lead-calcium from other manufacturer's docs, I always come away with a few things:

To get the rated cycle life out of them, if you can't meet the minimum recommended charge current regularly, at least do so when you can. A poor analogy is treating your agm's to a deep-pore scrub by discharging them to say 50% and hitting them with a lot of current. Otherwise, if all you do is tickle them, then that is like taking a sponge-bath and eventually your pores will clog deep down.

In addition to this, they do need to be *fully* charged as often as you can manage it. Hence, a flooded may actually be better in a repetetive 50-85% charge situation where you can do an EQ (or perhaps run with agm's that can do that.)

But to be truly honest, this is all manufacturer research on my own, since I don't know if I have enough life-years left to prove it.

The skinny on pure-lead - turn back the time machine to the Gylling group where all you had was Optima and their baby competitors - Hawker Cyclons. The deal here is that with pure-lead, you have extremely low internal resistance, coupled with tight physical compression. Later, this form of compression went from spiral-winding techiques to flat-compression techniques as evidenced by the Odyssey line where the flat-plate material is about 30% larger than the battery case and they smash the plates together. With the flat-plate, it merely has more capacity due to shape. No big deal, unless physical space is a major concern. The story goes that with such high physical compression there is no need for calcium doping for strength in addition to less internal resistance, AND the active paste material won't shed under harsh treatment or high current charging as it has nowhere to go. The two lines were marketed to consumers with the Optima, and commercial users with the Odyssey. There is much more history but no need to go there now. However I would like to dig up more information about the specifics of the earlier batteries (lab built obviously) in the moon-rovers.

The end result is just that you can hammer them with current with less heat generated in the process as there is no calcium doping limitation to overcome. Great for low solar-insolation areas, but the physical and financial practicality of meeting these minimums may force the use of an AC charger / generator once in awhile to maintain them in good health.

I can say I was impressed that when I purposely purchased a few two-year old Odyssey's, with only 11.9 and 12.0 volts ocv, they perked right up after only two or three regular charge cycles. Measuring them on a West-Mountain Radio CBIV analyzer showed that they had about 90% rated capacity. I was happy, yet there was no denying that they had two years on the clock at purchase.

westbranch

Re: What is the optimal SOC range for cycling AGM batteries

Not much time to comment so point form...

re position , from Absolyte rep. Electrolyte can 'wick' up 8 inches in their cells so standing vertical will leave a sig portion of plates dry, hence lay on sides

Absolyte has a 20 yr or longer life in standby app.

Have been told by C&D that their batts are not 'designed' for cycling in an off grid app so not 'recommended', no comment about how it would work. trying them as mine were in a float service for 5 yrs and warranty was 7 yrs. Further discussion with C & D about charging parameters...

in the meant time I found this helpful publ. on FLA and VRLA characteristics, and HOW TO CHARGE THEM
http://www.cdtechno.com/pdf/ref/41_2128_0212.pdf

from what I read a FULL charge periodically is essential to longevity.

back next week.. cheers