Robert Bruninga via EV wrote:
A quality GC2 golf cart battery (Trojan, US Battery, etc.) is 220-240
amphours at the 20-hour rate, and costs $75-$150. They are good for 5-10
years, and 600-1200 discharges to 50% or so state of charge.
No, not BOTH. One or the other. 5-10 years just sitting there doing
nothing but waiting for the grid to go out (4 hours a year around here)...
Correct. They are "used up" once they have accumulated 600-1200 cycles,
*or* are 5-10 years old.
OR they barely will last 2 years in daily solar-off-grid use (and note, you
are only getting 50% of their capacity just to last that long)...
That would be the case if you discharge them 50% or so every day. But
50% is an excessively deep discharge if you're going to use them every day.
For daily use, you would limit your depth of discharge to just 10% or
so. Then they would still last for their calendary life; 5-10 years.
Note that life is a function of depth of discharge for *all* types of
batteries. If you expect them to last, the shallower the discharge, the
better. You'd also murder a lithium pack in a few years, if you deeply
discharged it every day.
If you really have a situation that requires daily deep discharges, you
probably have to use the old Edison nickel-iron cells. Aside from
quality or abuse, they are the only type with an indefinite cycle life.
(There are 100-year-old Edison cells still in use).
Yes, may as well just throw $6k in the trash every few years since you never
use them. The cost of the electricity for the 4 hours average outage per
year is only about 80 cents. (1 kW for 4 hours). Amazing how many people
will spend $6k for that 80 cent problem.
I see a pretty heavy thumb on the scale here, Bob. :-) $6k of golf cart
batteries is about 60 of them; that's around 80 KWH of storage! Who on
earth needs that much for a home.
You have to select the size and type of battery according to the
application. Some will be best served with lead-acid, some nickel-iron,
others lithium etc. Some applications aren't appropriate for batteries
of any type.
If all you have to cover is 4 hours of outage per year, then dumb old
lead-acids are going to be the cheapest by far. Like I said, they will
die of old age before you wear them out.
--
Don't worry about people stealing your ideas. If your ideas are any
good, you'll have to ram them down people's throats. -- Howard Aiken
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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