Battery Bussing [RE-wrenches]

[Joel Davidson]

1. If you have a battery with one series string of cells, you are drawing
current from one end. No problem.
2. If you have a battery with 2 or more series strings in parallel and the
paralleling cables are sized properly, it should not matter what point is
connected the load because the paralleling cable(s) is a common bus.
3. More cells are more chances for cell problems. So true.
4. More parallel strings are more chances for resistance problems. So true.
5. Most battery designers limit to 4 or 5 parallel strings by convention.
6. Most battery installers limit to cells or batteries that can be handled
(in)conveniently.
Nothing new here. Any other other "rules"?

Kurt Nelson wrote:

> 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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