On 6/2/2011 6:44 PM, d...@foxfire-energy.com wrote:
What I like best about Mark's set up (the retired phone co. dude w/
half a hand), is that he can select individual strings at random. he
can eq an individual string, or top off a few strings and park them.
he can even run strings of T 105s, or even nicad (individually of
course) in the same system as L-16s and the like.. he just reprograms
the chargers (and logs it). I think he got the design from his days in
the Navy.
So boB, how about a controller that can be user programed to charge
multiple battery configurations with a soft switch? i.e. Bank A, Bank
B...? and while you're at it, maybe a multiple string DC box?
Something with a shunt and a breaker for each string? A four string
set up would be nice.
I could use 2% of your first million.
db
Well, It's not a bad idea ! I'll forward that question off to Robin.
I have ran into several that use separate and independent battery banks
and switch between them. I'm not sure why they don't just use those
L-16 size
2V cells though instead.
But as I mentioned before, I think that a battery balancer device would take
care of problems with single strings but maybe even parallel strings,
as well as the pesky problem of AGM batteries that like to plump when
you cook 'em ! (I hate when that happens and one battery gets real hot)
Say, maybe a gizmo that goes across each battery (no 2V cells though) to
keep each
battery in the string at the same voltage. It would have to be cheap,
maybe $30.
Great discussion.
boB
Dan Brown
Foxfire Energy Corp.
Renewable Energy Systems
(802)-483-2564
www.Foxfire-Energy.com <http://www.Foxfire-Energy.com>
NABCEP #092907-44
-------- Original Message --------
Subject: Re: [RE-wrenches] 24 volt Battery Bank comparison
From: boB Gudgel <b...@midnitesolar.com <mailto:b...@midnitesolar.com>>
Date: Thu, June 02, 2011 8:56 pm
To: RE-wrenches <re-wrenches@lists.re-wrenches.org
<mailto:re-wrenches@lists.re-wrenches.org>>
Nobody mentioned this in this thread, but it occurs to me that the
answer may be made clearer
by looking at the Voc of each battery string after so many
Amp-Hours (years) of service.
i.e., disconnect the strings' parallel connection and measure the
individual string voltage after charging them all the best that
can be done.
This would be making the assumption that the batteries themselves
were fairly equal capacity and voltage at installation time.
And for whatever reasons, connections, temperatures and everything
else discussed here, the strings degrade differently.
The older and more worn out batteries should have a lower voltage
(Voc) than the less worn out strings. Thus, the better strings
may be tending to hold up the worse strings by dumping charge into
them when the whole bank is discharging,
and wasting energy and battery efficiency.
I guess that just large 2V cells are the answer in this case, if
at all possible.
Thanks for the help on this question !
boB
On 6/2/2011 10:42 AM, Tom Elliot wrote:
Not surprised at all about the phone company guy. It was a phone
company guy who read me the riot act that no one in their right
minds would ever parallel battery banks the way PV off-grid
systems did and got me to set up my system with separate strings
connected independently to buss bars. The battery engineer I
talked to years ago at Dynasty not only said the same thing but
also said keeping strings separate meant individual string
distance from the bars became irrelevant (given correctly sized
wire for each string’s parallel connectors). I had a system with
12 100 amphour strings of paired 12v Dynasty AGMs which was rock
solid until the day I sold the house. The last time I checked
the system before the sale no single battery varied from any
other in the system by more than 1/10 volt and the majority were
still holding identical voltages.
*From:* d...@foxfire-energy.com <mailto:d...@foxfire-energy.com>
*Sent:* Wednesday, June 01, 2011 4:14 PM
*To:* RE-wrenches <mailto:re-wrenches@lists.re-wrenches.org>
*Subject:* Re: [RE-wrenches] 24 volt Battery Bank comparison
Good thread. Thanks.
In my experience, it all boils down to the customer. I've seen
one temp. set up with like 12 strings (for a concert). but they
were recharged and sold individually within a few weeks.. I've
also seen a single string (Teledyne aircraft batteries) fail in
less than a year.. they were in a brand new airplane tug that was
never charged -- ever. (the guy said "I dunno, it just stopped
working").
I have one customer who (last I knew) was running 6 strings of
mixed aged L-16s going on 8 years. Thing is, he's a retired phone
company dude (Who's missing half of his right hand from using one
of those pocket pal screwdriver thingys on a key chain in a hot
DC rack.. like he'd done hundreds of times before.. but that's
another tale). But I do like his set up.. he has each string set
up with it's own fused Disco and Trimetric.. Gives him random
control over each string. And yes, he keeps a very detailed log,
and you can bet that when he takes a battery out of service, it's
done.
Me? for an average bullet proof off grid system, I shoot for a
max of two strings for 24V systems (for the redundancy), and
manually reconfigure them every few years. for 48V systems, I
shoot for one string of two Volt cells.. thinking that if I loose
a cell I can still operate a 46V system until I get a replacement.
And Yes, as we all know, there are folks out there that really
shouldn't be allowed to operate a popsicle stick.
db
Dan Brown
Foxfire Energy Corp.
Renewable Energy Systems
(802)-483-2564
www.Foxfire-Energy.com <http://www.Foxfire-Energy.com>
NABCEP #092907-44
-------- Original Message --------
Subject: Re: [RE-wrenches] 24 volt Battery Bank comparison
From: Michael Welch <michael.we...@re-wrenches.org
<mailto:michael.we...@re-wrenches.org>>
Date: Wed, June 01, 2011 1:43 pm
To: RE-wrenches <re-wrenches@lists.re-wrenches.org
<mailto:re-wrenches@lists.re-wrenches.org>>
Every now and then I see reference on this list to the need
for thermal detection. Here is an interesting, inexpensive
piece of equipment that could be used for finding hot (loose
or corroded) connections, hot batteries, hot PV cells in
modules, and even poorly insulated spots, its original
intended purpose:
http://www.blackanddecker.com/power-tools/TLD100.aspx
I have one and used it for finding uninsulated spaces, but
cannot attest to its durability or suitability for the other
uses mentioned above.
boB Gudgel wrote at 01:00 AM 6/1/2011:
>This might be a good reason for an installer to have one of
those FLIR (or similar) thermal imager cameras.  They're a
bit on the expensive side, but could
>really be helpful for so many things.  Even just to know if
you have left a nut loose (under load of course)
>
>boB
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