HI Allan,
so right you are.
Thanks about the surrette link.
There batteries sure seem to be prone to odd things in the PV world.
peace,
jay
On Aug 3, 2008, at 5:12 PM, Allan Sindelar wrote:
Jay,
You're right about leaving off the post at the bottom - whoops.
It's at the bottom here.
About voltage drop: I meant only that by running the array at a
higher voltage than the batteries, there could never be sufficient
hot-weather and undersized-wire voltage drop to prevent the array
from exceeding the EQ voltage of the batteries. This is most often
a potential problem with 12V systems. I mentioned it only to
eliminate it as a possible cause of this situation.
The Surrette Tech Bulletin 614 is available for download at http://
surrette.com/files/BU-RS-614.pdf. My understanding is that this
bulletin is the direct result of the complaints on this list about
two years ago about Surrette battery performance and life.
Allan
-----Original Message-----
From: jay peltz [mailto:[EMAIL PROTECTED]
Sent: Sunday, August 03, 2008 1:41 PM
To: Allan Sindelar
Subject: Fwd: [RE-wrenches] Surrette Battery Question
HI Allan,
You mention about a Surrette tech bulletin, I can't seem to find
it? Can you tell me where it might be on their site?
Also I"m curious about you saying that hot modules isn't going to
affect voltage drop.
Sure it will. If the wire is upsized for the lower voltages from
hot weather, then you've compensated for it, but there is still
added voltage drop.
And about the adding new panels to old? I didn't see the link/post
at the bottom?
Thanks, jay
OK, the story,
This client had started off-grid in the early nineties with a tight
budget. He and his wife would add modules as they could afford
them, usually used. The built a homemade tracker with a Wattsun SA
controller and two linear actuators, using a DPDT momentary switch
to adjust elevation seasonally. Over time the tracker filled out
with eight Arco 16-2000s, nine Carrizo (Arco) M52L 5V Quad-Lams,
two BP 275s, and two old square whatsises with 2" cells from the
seventies.
Eventually their income increased and their house and house loads
got bigger. They asked us to upgrade their array, which eventually
led to the 8 160W modules I added on a pole-top array. There were
several catches, though:
1. They wanted to keep as much as possible of the original
"democracy tracker" in operation;
2. The house had grown over the years, and the existing tracker had
to be moved 50' farther away;
3. The balance-of-system was still in the original basement, now
inaccessible from the outside, as the house had been expanded bit
by bit in all directions.
4. The #2 (or 2/0, I can't recall) USE copper array input wires had
been built over and couldn't be replaced; we had to use them.
We dismantled the tracker and moved the pole (yep, lifted pole,
concrete and all and set it in a new, larger hole with more
concrete). We put a 3R j-box where the old pole had been and
trenched to the new locations. After playing with different
calculations, we changed the old tracked array as follows:
1. We added two BP 380s (the closest we could get then to the older
275s) and wired them as one 48V string;
2. We dumped the whatsises, which had low output;
3. Now I'm trying to remember: I think I wired the four 16-2000s
(originally 2.2A at 12V) in parallel, then wired this set of four
in series with the nine Quad-Lams (think of M52Ls, originally used
in the Carrisa Plains utility central power plant in California
from 1984-1989 or so, as similar to 16-2000s but with the 3 rows of
cells wired in parallel, to make about 7A at 4 1/2V nominal. That's
why they're called Quad-Lams: it took four in series to charge a
12V battery).
So we ended up with a 17-module array wired at 48V nominal, tied in
with the new 48V array. What made it so special, other than that
it's the only 17-module array I ever built? When we were all done
and it was charging the 24V battery through the MX60, I alternately
turned each array off and let the MX60 find its MPPT voltage: the
two arrays were within one volt of each other. We got it right, and
I have always been especially pleased with that job.
That's all.
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