Posted by Ron Rosenfeld on July 30, 2008, 8:51 pm
On Wed, 30 Jul 2008 11:16:30 -0700, wmbjkREMOVE@citlink.net wrote:
It's hard to keep all of his recommendations straight. But I thought the
300Ah battery went along with the 17- 50W panel recommendation.
Oh, I suppose you could include the 2AS1100 as a sequel to #3, but I didn't
include it separately because he didn't specify it as part of a system, and
we have no idea how many he would have spec'd (maybe he would have had four
of those in parallel, also).
At 245A draw, my Peukert related calculations show that it would last for
"just long enough" -- 31 minutes. And the simulation on the day that
battery gets to its lowest SOC (35.6%) doesn't show any Unmet Load.
And that's with a 9 panel - 50W array.
GG -- the serendipitous solar deeziner.
Posted by wmbjkREMOVE on July 30, 2008, 10:11 pm
On Wed, 30 Jul 2008 16:51:41 -0400, Ron Rosenfeld
I needn't be so charitable. :-) When one of his deezines includes a
particular battery spec which he subsequently changes, then to me it
constitutes a new deezine. Although everything past 2 attempts might
as well be 100.
That does seem more intuitive and less extreme. Does the simulation
deduct the array current from the load current? Account for aging?
Specify a lowest-voltage? I'm wondering if apparent voltage might drop
low enough to trigger premature inverter shutdown.
Especially the "dip" part. :-)
Posted by Ron Rosenfeld on July 30, 2008, 10:49 pm
On Wed, 30 Jul 2008 15:11:16 -0700, wmbjkREMOVE@citlink.net wrote:
Yes, it assumes any current from the array will go to the loads. I think I
mentioned earlier that I had the pump run during the late morning hours.
It assumes the battery performs to the mfg specs and does not account
specifically for battery aging. I don't know what the Battery Energy
warrantee is, as that page is "under construction". Surrette warrants
against "failure" -- but don't specify whether that means failure to meet
published specs, or a dead cell. In the US, at least, unclear warrantees
are interpreted in the favor of the consumer.
One can enter a derating factor for the panel to account for, among other
things, aging. I used 90% to be "compatible" with what George seemed to
enter in his spreadsheet.
No, it does not compute that, but it won't allow the battery to fall below
the specified minimum SOC -- 30% in this case.
Interesting question that none of us has yet considered.
What happens to the voltage of a nominal 12V 620Ah battery that is at a 40%
SOC with a current draw of 245A?
Posted by wmbjkREMOVE on July 31, 2008, 12:49 am
On Wed, 30 Jul 2008 18:49:19 -0400, Ron Rosenfeld
Then the deezine is busted on yet another basis, because it's already
marginal and George has previously refused to accept the concept of
running loads at the most advantageous times. Without that strategy,
discharge current would be perhaps 15A higher.
It'll be interesting to read the deeziner's explanation of where he
took aging into account. <snorf>
I don't think it would be good. I have some small loads connected to
an Exeltech inverter with a fixed low-voltage cutout setting. When my
batteries are still relatively full, concurrent large loads
(successive instances of 4hp compressor starting while running plasma
cutter at max in addition to normal house loads), the Exeltech has
occasionally tripped off even though the SWs doing all the work don't
complain. Then again, the issue probably don't apply to the deezine at
hand since George has thoughtfully specified one of those special
882.35W inverters, and he alone holds the secret to how well they
start and perform with a 2500W load. :-)
Posted by Ron Rosenfeld on July 31, 2008, 1:30 am
On Wed, 30 Jul 2008 17:49:08 -0700, wmbjkREMOVE@citlink.net wrote:
Interesting. I've never had my SW5548's trip due to low voltage since we
moved in. But I don't think I've ever had a situation where the current
draw represented a significant fraction of the (residual) capacity of the