The bottom battery provides 26.7 amps of this. The next battery up provides 23.2 amps. The next battery up provides 23.2 amps. The top battery provides 26.7 amps."
...the author goes on to suggest a single post or bus bar solution.
While it doesn't make sense, I have seen others make this same observation. Perhaps it's the inner batteries being warmer, though I would think they would contribute more not less. Perhaps it's some field disturbance from measuring the inner vs outer batteries. If it was a minor variant WTH, but I'd say this is significant.
Battery internal resistance = 0.02 Ohms
Interconnecting lead resistance = 0.0015 Ohms per link
Total load on batteries = 100 amps
The bottom battery provides 35.9 amps of this.
The next battery up provides 26.2 amps.
The next battery up provides 20.4 amps.
The top battery provides 17.8 amps.
So the bottom battery provides over twice the current of the top battery.
Not wanting to dwell at all on the nature of the batteries on this system ...
Sometimes, particularly it seems, on 12 V systems, batteries are added to the system over a period of time. Of course this in, and of itself, usually creates imbalances of its own. Am not saying that this was the case with this system.
Agree, that wiring will probably not be the be all, and end all for any/all imbalance.
Just the physical size of this battery bank, and likely temperature variations across this bank, plus, the probable inability of selecting one battery that is representative of the entire bank, on which to place the necessary BTS/es can be a real challenge. Having accurate charge and Float voltages is very important for battery health, and the temperature effect on these voltages is fairly high for many off-grid Flooded battery banks (as they are often in unconditioned spaces).
Also, of course, ageing of batteries will not leave many strings that were once-balanced, balanced some months later.
Having a battery bank that is composed of many, many batteries (in parallel at that), will; give the manager of the system an opportunity to measure current balance and SGs often, and probably often, move batteries around to try to maintain balance, and/or to charge batteries and strings individually in order to try to bring lagging batteries in some semblance of balance with others.
Measuring the voltage of individual battery voltages, ideally with high charge or discharge currents, can often give a quick indication of approximate balance, when compared to the voltage of other batteries in the bank.
Please be very careful, when connecting and disconnecting battery cables to move or individually charge batteries, due to energy and possible explosion hazards that can exist. Sometimes a small mistake, like dropping a wrench, etc can cause a surprise.
FWIW, not to try to be too preachy. Best of luck, Vic
Hi Kevin, Thanks for the messages.
Most Lead Acid batteries should be cycled below 90% State Of Charge (SOC), before recharging them fully. And cycling them to 80 or 75-ish percent SOC is actually good for Flooded batteries.
Had read that Thread on Optimal Charge current (or whatever was its exact title), several times, and did not really know how folks got the idea that the batteries were not being cycled deeply enough, other than the possible assumption that each and every cell was fizzing during Absorb, perhaps due to overcharging.
Mike 9????? mentioned that Absorb should not be extended past one hour, which would only be the case for a very lightly-cycled battery. Just to make certain that you know, a Flooded battery that is cycled to about 80 % SOC would probably require two or more hours of Absorption, perhaps three hours, when using recommended Absorb voltage.
Managing batteries can take quite a lot of time, and parallel strings will take some additional time.
Many folks believe that AGM batteries require NO maintenance. This is not true, they just take a different kind of maintenance, primarily due to the difficulty in knowing what is the actual SOC the batteries.
You will probably end up culling a few batteries, and this will help reduce the number of strings, unless you absolutely must have that Capacity.
Please DO stop back to let the group know how you are doing, as this is a friendly and knowledgeable group.
GOOD LUCK, Thanks, Vic