I follow what Vicron, Schneider & other top manufacturers engineers recommend.
Battery Cable length from Batt Terminal to end "Device" (Inverter/AIO) should be of equal length and kept together (reduce & manage RFI/EMI). Wires should be of the same size (AWG), grade & quality as consistency is essential. This is from Lug to Lug length excluding devices like fuses/breakers/switches etc.
- Do note that every "item" in-line adds resistance and this can add up cumulatively and must be accounted for and settings adjusted accordingly.
Battery Packs in Parallel is where irregular wire lengths become very apparent and quickly...
Example: A typical system with 4 (Matched & Identical) packs in parallel with varying wire lengths will work but when charging for example, the battery with shortest wires will charge higher & finish sooner than the one with the longest wires who will come in last and never fully match to exactly equal ##.00 Voltage, That one will always have the lower SOC at the top and will discharge the last being a touch higher than the rest. There are other "common symptoms" that rear their ugly heads due to wire length & resistance issues.
Many people chase after BMS settings and attempting various calibrations, balancing tech and more while the root of the problem is rarely addressed. Many do not even realize that a FUSE adds quite a bit of resistance in-line with some being worse than others ! All of that needs to be accounted for.
When you get to serious calibration to match everything up and account for the OFFSETS between charging & discharging and YES, the Voltage Offsets are DIFFERENT when charging OR discharging making things even more interesting.
A simple test for that:
- When charging, use a 2 decimal accurate DMM/DVOM and look at the voltage at the SCC or Inverter OUT Terminal to Batt and at the Batt Terminals (if component system, the SCC & Inverter/Charger will each have different values) and you will see a drop from Input Power to Batt Terminal.
- When discharging do the same steps as above and again you will see a difference between the device & batts
-- In both instances, the battery packs should be at the same voltage ##.00 +/- 0.02 on average IF all wires are the same with the same resistance.
Many Tier-1 products have OFFSET settings to adjust for this, often times it is only 1 offset and not for both charge or discharge offsets. This must be manually corrected in your settings with the Voltage @ Batt Terminal being the guidepost.
In closing, this is a previously contentious subject, as I said, I go with the designers & engineers from Tier-1 Companies as well as my personal experience over the years.
Hope it helps, Good Luck.
Steve