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Repost please: $/watt solar panals. - Page 8

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Posted by wmbjkREMOVE on October 29, 2009, 2:39 pm

My batteries are 14 years old and still going strong. There's a pretty
good chance they'll make 20, which is their nominal lifetime rating.
They're the bare minimum size in the context of my consumption -
generally between 12 and 15kWh per day. Only a fraction of that makes
a trip through the batteries, which is as it should be for any
well-managed setup.


Posted by Josepi on October 30, 2009, 5:06 am

I still haven't heard of anybody.

Posted by daestrom on October 30, 2009, 8:28 pm

Josepi wrote:

Well, these aren't exactly 'cheap', but are guaranteed for 3300 cycles.

If you discharge/charge about 1/2 a cycle per day and immediately
recharged it, that 'should' last 6600 days that would be 18 years.

Problem is, solar applications are more like discharge 30%, wait 8
hours, charge 20%, discharge another 30%, wait 8 hours charge 25%, etc...

That kind of 'cycle' is pretty hard on any battery.



Posted by wmbjkREMOVE on October 31, 2009, 12:42 am



That scenario should only be happening during multiple-day dark
periods. For typical installations, the rest of the time the routine
discharge should be less. To make the math easy, figure 4 days supply
and 20% reserve. Which makes a sunny day's dark-period discharge
perhaps half of a day's consumption - 10%, then back to full by early
afternoon. It depends on the owner's habits though. If they tend to
leave early for work and arrive home late, and had no daytime loads,
then most or perhaps all the consumption might make a trip through the
batteries. Then I could see how it could come close to your scenario,
in winter at least.

I think that's what's worse are setups where the batteries get
deep-discharged, and then on the first sunny day it's charge back to
50%, discharge back to 30, charge to 60, back to 40 etc. I've seen
that scenario a lot, and when you combine it with (most) owners who
don't have a convenient way to gauge battery charge level, it's easy
to see how some installations have short-lived batteries. I really
lean on people to get and use battery meters. Then they can see right
away if their full-charges are too infrequent.


Posted by Josepi on October 31, 2009, 4:12 am

Yup when the battery meter says dead for the whole of December 'cause the
sun has been cancelled my batteries are really gonna' last for 20 years,
like yours do (try to convince us you are real).

Let's face it, you think you are gifted in the alternative energy department
and in a few other ways. We doubt you would be able to get away with your
bullshit in a real environment where you have to actually provide energy to
live from and not just play Superman online.

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