L-16 "cycling" requirements? [RE-wrenches]

[David Palumbo, Independent Power & Light]

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What Ray says goes along with what Richard Perez wrote in "The Complete
Battery Book" in 1985. "In general, if we have the ability to fill the
batteries at will, then a depth of discharge of 80% is the most efficient
overall for deep cycle lead-acid batteries. This figure is derived from many
interrelated factors and much practical experience."

Since, in off-grid systems, we rely on pv to charge the batteries and back
it up with generator power (unless you are fortunate enough to have wind or
hydro also). We are obviously not always using 80% discharges. We should
strive for good designs that other wrenches have talked about here already.
At least C/20 pv charge rate.
7 to 10 days of autonomy in the battery bank.
Proper voltage and absorption settings on your charge controller, and or,
inverter/charger.
Homeowners trained to pay proper attention to their Tri Metric amp hour
meters.
Make sure batteries are fully charged at least once per week.
If all that is done (along with a good install and proper maintenance) then
the batteries will last a long time.
Dave


<< An interesting point on cycle life vs DOD is that you really only get so
many KWH out of a battery, regardless of Depth of Discharge. Just multiply
20% DOD times its cycle life and compare that to 80%DOD and it
corresponding lower cycle life. The total amp hrs are almost the same (at
least for Trojans, which is what I was looking at). Interestingly, you seem
to get fewer total amp hrs out of the battery at 10% DOD.

I wish we could attach low res GIF files sometimes to graphically show what
we were talking about. What about it Michael? limit the file size to 15 KB
maybe? It would sure help to show wiring diagrams and charts sometimes.
Probably less total traffic too , since we would have fewer
misunderstandings.
Ray Walters>>

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