Cooling the batteries

Ouch, providing the local water source for pests was something I hadn't considered.

While not shown in the picture the box has a lid that is usually left open to facilitate heat escaping.       There is also an exhaust fan.      You can see the 2 air intake holes in the box which are covered with heavy screen.       Those intake holes double as an emergency overflow release.      I never wanted to risk the water getting overly full and into the outer battery cases or under the rubber liner so those holes are a bit lower than the top of the pond liner and battery tops.

Since the box needed to be raised off the floor to allow for a drain the box has 2x4s insulating it from the concrete.       The boards are spaced so if I ever get water under the box it can get some airflow and dry out. The outer wood band surrounding the box like a belt is to reinforce against the water pressing out on the sides.

I wanted to make the box more square and stay out from under the electronics but putting the batteries in 2 rows would have made maintaining the batteries a monthly torture having to reach over the 1st row of batteries to reach the 2nd row. 

jonr said:

IMO, the optimal design is a large chiller and a large water tank such that all the water cooling can be done when you have excess power and there is no charge effect on the batteries. 

Waterwheel's numbers indicate that there would be some benefit to more water. 

Actually my current numbers indicate that there wouldn't be much advantage to using a large tank of pre-chilled water and I may have been able to get away with a 1/6 hp chiller.        The chilled water holds well through the night.
The chiller has been off since 6pm yesterday.      At 7:30 am today the batteries were 73 and the air in the garage was 79, I didn't check water temp but I would assume about 73 degrees, same as the batteries.     The batteries went down to 76% SOC so we're getting a good hard charge today.     Cloudy earlier but 84 amps going in at noon when the controller went into float yet the batteries only went up to 77 degrees.      The chiller timer runs the chiller from noon to 6 which is when the heating is the worst but as the days get shorter I'll shut the chiller down earlier.

I'll post the days numbers at 6 after the sun is mostly off the panels.

Using your formula and considering the 77 degree temp most battery manufacturers use  I see my batteries aging an extra 4-5 months per year.       Of course during the winter that aging process probably slows below the average expected aging rate at 77 degrees but let's say that because of heat my batteries age 16.5 months for every year (4.5 months well over 88 degrees. and often over 100 degrees).      That means every 5 years the batteries go through an additional 22.5 months of aging (4 years worth of excess heat related aging if they last 11 years).      

After freight charges I'm using a $10,900 set of batteries (hurts to even type that big number).     That's $1090 per year for batteries if they last the 10 year warranty period or $5450 for 5 years.       Assuming the $600 water chiller and pump lasts 5 years but saves about 2 years worth of heat aging that means the $600ish investment is saving me roughly $2200 over a 5 year period in addition to delaying the wonderful job of replacing those 340 lb batteries for an additional 4 years (theoretically).

I understand that these are all theoretical numbers but we've all seen how batteries in Canada last a lot longer than batteries in Tucson AZ.       
Using your much lower 1.5 months additional heat related damage means I'd save about $75 over 5 years when you conceder chiller cost vs battery wear cost so I'd say that your 1.5 months lost life per year of service is about the break even point as to whether or not using a chiller is financially worthwhile.

Fun fact,       In an effort to make putting the batteries in the water box easier I attached the pond liner and front wall of the box in such a way that the front wall of the box can be folded down flat on the floor in front of the box.        This allowed us to not have to heave those batteries up and over to get them into the water box.