<html>
<body>
<font size=3>Colleagues:<br><br>
I found Tom Elliot's buss bar solution intriguing, but instinctively
something bothered me about it. Although I like fondling wiring
hardware as much as any of us, this procedure seemed to unnecessarily
complicate the battery cabling system. Each added cable and each
added connection point contributes actual resistance and potential
problems.<br><br>
I undertook to simplify this into an electronic circuit with each cable
represented by a resistor (which it is) and at the same time
providing a clear depiction in which one can count the cables and
connection points for each of a number of battery strings. The
result is a simple PDF drawing on our web site:
<a href="http://millersolar.com/" eudora="autourl">http://millersolar.com</a>
Go to "Case Studies" and find Battery Wiring Options as the
last entry. I welcome each of you to poke holes in my analysis,
graphics and/or analysis.<br><br>
Please note the balance achieved in both systems. The merits then
lie in the actual number of cables and connection points, IMHO.
Lastly, consider the labor and materials required in a either
installation.<br><br>
Sincerely,<br><br>
William Miller<br><br>
PS: I have a pathological dislike of splices or connections that
are not mounted to a surface -- when secured you always know where they
are and they are easy to get a probe on. This is why we use power
distribution blocks whenever possible. Polaris connectors in a
battery compartment don't seem right -- they could easily trap corrosive
fumes and hide corrosion problems from view.<br><br>
Wm<br><br>
<br>
At 09:59 AM 12/4/2009, you wrote:<br>
<blockquote type=cite class=cite cite>Hi Kent,<br><br>
I am sorry but I disagree with your conclusion that it only keeps the
wire resistances the same for 2 strings. This diagonal system,
which I believe many people would call 'reverse return' in the states,
actually provides for exactly equal resistance on all paths to all
strings. Each time you add a link in the positive path you remove
one in the negative path. I admit that the voltage drops will be
very slightly different due to different currents in the various links
but the differences now are so tiny that I would not worry about
them.<br><br>
I agree that you will get imbalances in multiple battery strings at times
- usually during periods of prolonged low winds. But you cannot
persuade me that multiple strings 'don't work right' because they are
used in most of the systems I work with since the 1970s. I see just
as much sulphation in large capacity cells as I do in small capacity
cells (in multiple parallel strings). I would say that going from
12-volts on up to 48-volt systems has caused me a lot more headaches with
unequal battery states than paralleling a lot of batteries has.
Batteries connected in parallel will tend to take what they need.
Connected in series they take what they are given. Also, a cell
failure in a 12-volt system attracts attention at once, whereas a cell
failure in a 48-volt system can be overlooked for much longer.<br><br>
There are plenty of points of view about batteries :-) Part of it
is the difference in mentality between solar users (who count out the amp
hours and know exactly what they have to work with each day) and wind
users (who can party like mad sometimes and then have nothing at other
times).<br>
<br>
Hugh<br>
</font></blockquote></body>
</html>