Michael K Johnson wrote:
I had seen references on list to Interstate deep cycle batteries, and
thought that their marine deep cycle batteries were so; I was looking at
the SRM-27B.
As soon as you see the word "marine" in the name, it's not a true deep
cycle battery. It is a battery good for something like 100-200 deep
cycles. A normal SLI (Starting Lighting Ignition) battery is good for
perhaps a dozen deep cycles. A true deep cycle battery (like a golf cart
battery) is good for 600 or more deep cycles.
> 1.2565 and a 100A (worst case, I hope!) ~30 minute discharge time.
The cycle life also goes down as the current and depth of discharge go
up. 12v battery life is only rated at 25 amps, while 6v and 8v batteries
are rated at 75 amps. So if you are discharging at higher currents, the
benefits of a true deep cycle battery are even greater.
If you're only going to mow once a week, and only for 6 months of the
year, then a "marine RV" battery might be good enough for a year or two.
But if you expect more life, see if you can crowd in deep cycle batteries.
A 30-minute discharge time is quite short. This is the range in which
AGMs often excel. They lose less capacity and life as a consequence of
high discharge currents (and thus short discharge times) than flooded
batteries.
Or if you can afford it, go to lithium.
Golf cart batteries are big. I'd have to figure out whether I could even
fit them on this platform. I don't think I could fit 8 6V golf cart
batteries. The 12V golf cart batteries I've seen are all too big to fit;
the group 27 size are a tight squeeze, and say a set of four Trojan T-1260
I don't think I can find a way to fit. 6 8V T875 would have more runtime
than I need and I haven't figured out how I would fit them either though
it's probably more likely to be possible.
Well, you don't *have* to use 48v. The ElecTraks were 36v precisely
because it meant they only had to fit in six 6v batteries.
12v group 27's are 7" x 13", so four of them are 364 sq.in. Perhaps you
can use six x 8v = 48v? Each one is 7" x 10" so that's 420 sq.in. Or
maybe five x 8v = 40v, and 350 sq.in?
--
We live in a society exquisitely dependent on science and technology,
in which hardly anyone knows anything about science and technology.
-- Carl Sagan
--
Lee Hart -- See my Xmas projects at www.sunrise-ev.com/projects.htm
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