12thgenusa wrote:
MrWizard wrote:
your assuming, in storage, fully charged no use, only parasitic drains, and full charge everyday, replacing the tiny self discharge drain
Not assuming anything. It's documented by the trimetric and the data log of the controller. When the solar comes on in the morning it spends a period of time in MPPT, a few minutes in absorb and switches to float for the rest of the day.
Is there a DOD that defines a cycle? In my mind a period of charge followed by a period of discharge is a cycle. I'm not trying to defend the article, just trying to find out if there is merit to it.
Here's another quote from Wind & Sun Deep Cycle Battery FAQ.
"This does NOT mean you cannot go to 80% once in a while. It's just that when designing a system when you have some idea of the loads, you should figure on an average DOD of around 50% for the best storage vs cost factor. Also, there is an upper limit - a battery that is continually cycled 5% or less will usually not last as long as one cycled down 10%. This happens because at very shallow cycles, the Lead Dioxide tends to build up in clumps on the positive plates rather in an even film."
Be careful what you base all your suppositions on, the source may be lacking. For instance:"This happens because at very shallow cycles, the Lead Dioxide tends to build up in clumps on the positive plates rather in an even film." I believe this should read "lead sulfate" on plates. The plates, themselves, contain lead dioxide.
Further, one should know if the buildup of clumps rather than a film is especially deleterious to the health of a SLA and, if so, how appreciable that is.
MO is that shallow discharges are not an issue in the RV world. As mr. Wiz notes, a 5% discharge is almost de rigueur. Since we are able to critically maintain our batteries with onboard chargers, solar arrays, and independent maintainers the loss of battery health from many shallow discharges is just not an issue.
