nice solar system setup

How cold are your floor in winter? You should not rest lead acid batteries on cold floors as the temperature differential from top to bottom of each cell causes the electrolyte (sulphuric acid) to concentrate at the bottom if / when the cells are low on charge. This will eat away at the bottom of the plates inside the cells if the batteries are left uncharged for a while. I know it's a pain but I would put in a insulation board (say 25mm celotex) with a 19mm OSB / plywood sheet below the batteries as then you're mitigated against the cold floor. Also you should make sure that all the batteries are spaced apart from each other so that you don't get the batteries / cells in the middle of the pack hotter than the ones on the outside, this also messes with the balance of the battery pack over time. 25mm should be sufficient if you can arrange for a crossflow of air to vent the batteries, you don't need much ventilation just a slow steady airflow. You're not trying to cool the cells, just making sure that the minute amounts of hydrogen and oxygen doesn't get a chance to reach the a concentration where it will ignite if a spark gets in there...

Is that a brush less fan? I hope so sparks can make gas ignite. Nice job very well done. You are also going to have a very hard time finding a weak battery wired that way that is why people do it the other way.

I did it quickly and efficiently with instructions from Avasva webpage.