Battery Bussing [RE-wrenches]

Sat Sep 1 02:37:49 PDT 2001

I regularly wire inverters to the diagonally opposite ends of the battery
bank. If for some reason there are 2 inverters involved such as to cut
runtime on a generator or a dual system I feel it puts less strain on the
major positive and negative terminals to have the load split between the 2
ends of the battery.
I have always run the negatives from the shunt to each negative post, I just
think it will sort itself out and use both posts.

It seems that most of the battery failures I have seen or heard about are on
the major + or - terminals and that it might help to ease the strain on the
corner batteries to split the load instead dumping it all through one
terminal.
I also have been known to rotate the cables to the opposite ends of the
battery at some point if I am around for some reason. If you do that right
you don't even loose the reading on the meters. (kill the loads and use a
jumper wire to power the meter)

I also twist the battery cables (same pairs) and keep the size and length
the same.

Just my point of view,
Bob

RE. Ellison
Supplier of;
Diesel Generators &
Alternative Energy Systems & Supplies
34642 Countryman Road
Theresa, NY. USA
                              13691-2076

-----Original Message-----
From:	Kurt Nelson [mailto:sunwise at cheqnet.net]
Sent:	Wednesday, August 29, 2001 2:14 AM
To:	RE-wrenches at topica.com
Subject:	Re: Battery Bussing [RE-wrenches]

Joel wrote:

Question 3 - Will current flowing
> through any interconnect differ from any other? Question 4 - If batteries
are
> similar (same production batch and specific gravity) and cables and
connections
> are the same, under what conditions will interconnect current flow differ?

Hey Joel,

I don't know if I can answer this being that I asked the original question,
but I may be able to make the issue a little more clear.  Current flows
through the least path of resistance, so to keep from pulling more current
off one end of the battery than the other, the main cables are placed at
opposite corners of the battery pack (you weren't clear if this was the case
in the questions you posted).

It is in fact very similar to plumbing a solar thermal flate plate liquid
collector.  If you don't plumb the input and output to opposite corners of
the collector, the interconnecting tubbing inside the collector that is
closest to the piping receives more flow (wash) than the other end of the
collector.   Plumb it in from opposite corners and there is the exact same
distance/piping flow throughout the entire collector.  When a battery is
wired in from opposite corners, the flow through all bussing is even as
well.

I wanted to add a second inverter and place it on the opposite corners of
the battery from where the existing inverter is wired to get an even more
balanced draw on the battery, but as the seperate B- cables are bonded at
the shunt, it doesn't work out.   You end up with the inverters each drawing
off one end of the batery, though both from opposite ends.

Part of my question was that if the loads are somewhat balanced on the
inverters, and as the inverters are both used to charge the battery
periodically (at the same rates), is it still better to leave the cabling
for each inveter at their own opposite corners?

Sounds like no.  Perhaps this should only be done when doing dual SW's for
240 only.  Then they would be drawing very evenly off the entire battery.
The other time when this should be done is when using Trace's parallel
stacking interface kit?  Then they would also be drawing evenly.

Kurt Nelson

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