Cooling the batteries

Hot and humid here in the south east

The tiny water cooler is an interesting idea.         But I was just going to use the slightly cool well water filling daily when the batteries are in absorb and drain during the evening.       I figure a automatic cutoff like I use in the donkey's water trough means I wouldn't have to wait around as it fills and with a drain in the garage floor a few feet from the battery box would work for empting the box.

But building the water bath battery box and running the water lines along with daily filling is a lot more complicated than just hooking up a 48v thermoelectric cooling unit.

But is roughly 300 btu enough to even slightly lower the temperature of 2700 lbs in batteries?   I may be doing the math wrong but it looks like that 300 btu cooling power would take 9 hours to produce enough cooling to lower the battery temp 1 degree fahrenheit.     

It was an interesting idea.     

Jonr,
Where do you get your calculations of 10k btu per day heat from 20kwh cycling the from batteries?    It sounds about right but I'd love to play with that calculator.        During the summers with the AC I pull about 15 kwhs/day from the battery and less during the rest of the year.
Then in point 2 you seem to be saying 1 kwh energy would be sufficient to keep the batteries cool or remove that 10k btu which seems awfully low to remove that much heat using our less than efficient coolers available.

My water line is buried 18" deep and runs about 60 yds underground from the pump.      Tonight after running for a few minutes water coming out of the sink is 82 degrees so not so great for cooling batteries.        This matches up with my 8" in the ground temperature measurements (84 degrees).        I'm confident that if I dug 7-9' deep ground temps would be cooler but it's not realistic unless I dug a 8'x8' room 8' into the ground so I could add water to the batteries. Rainwater drainage that deep could be done but just a stupid amount of work and money to build that battery box.

My current thought is something like you and Softdown suggested.       A 1/4 hp water chiller for fish aquariums.    It draws 340 watts and cools about 1000 btu depending on the model.       Pump draws another 27 watts.       I could set it to run from 1-6 (summer hours) when I'm usually well into absorb and float with the house AC running.      Prices for a 1/4 hp unit run from $340 to well over $800.         More cooling power would help but I only want to run it when the panels are making extra power so I figure 1/4 hp is a good compromise.

Not enough to keep the batteries chilly but since it's power that I'm not using I could use it to keep the batteries a tad cooler.  I'm already putting a water fill and drain system in so replacing the water occasionally as Mcgivor suggested would be easy. 

Jonr,       Thanks for explaining the math.    But i doubt any cooling effort I make is going to double the life of the batteries, maybe more like a potential 20% life increase since the batteries are generally below 80 degrees about 4-5 months of the year and I've only going to get so much cooling effect in the 2-5  hours of excess energy that can be used for cooling per day.

Dave,     In many ways I agree that LI is a better choice and if the companies who made what ever lithium battery I chose had been making their models for over 5-8 years so I had a bit more confidence in their ability to have replacement BMS parts available say 12 years after I purchased the battery I would probably have gone with lithium just for the east of maintance.

Put the batteries in the water tight box yesterday, wired up this morning, and have some numbers to report.     
This is a commissioning charge so not a full blown bulk and absorb.      Batteries averaged 1.252 and 3.3v which seems a tad low for "fresh from the factory" batteries.      Since 5000 series batteries are double walled Rolls wants the outer cap of 1 battery temporarily removed so the temp sensor can be placed directly on a 2v cell.       I chose the middle cell and put the sensor where it was not touching the outer battery wall to assure accurate cell temp reading when cool water is surrounding the batteries.     There is about a 3/8" air gap between the outer wall and the temp sensor.       I haven't measured but the box holds about 80 gallons of water when filled 13.5" deep. 
  
Batteries were wired up, went through a short bulk and after an hour of absorb water was added:     Water chiller was not installed at this point.
pulling 48 amps, battery 90 deg,     just added water in box was 72 degrees, air was 89 deg.
30 minutes pulling 33 amps battery was 84 deg
60 minutes pulling 22 amps battery was 86 deg
90 minutes just went into float, battery was 86 deg      
after 90 minutes the air was still 89 degrees, water temp had risen 4 degrees to 76, batteries dropped 2 degrees.

While the 1st test was going on the 1/4 hp chiller was installed.      Batteries remained in float and chiller was started.     
start,             battery 86 deg, water 76 deg, air 89 deg
45 minutes    battery 84 deg, water 74 deg, air 91 deg
90 minutes    battery 84 deg, water 73 deg, air 90 deg
150 minutes  battery 82 deg, water 71 deg, air 90 deg
180 minutes  battery 81 deg, water 70 deg, air 89 deg

Not a hard charge cycle so not much heat produced.       Batteries in absorb using water chiller dropped 5 degrees in 3 hrs (about 2 deg per hour) while the air temperature remained about 90 degrees.       Water dropped about 2 degrees per hour.     The chiller is small but helps and the water will continue to cool the batteries for another few hours.

Update 3 hours later,     No chiller, just resting batteries in previously chilled water stagnant water (no pump running).       Batteries have dropped 1 degree to 80.      Water is up 3 degrees to 73.    Air temp has dropped 5 degrees to 84.

Years ago I picked the general area I wanted to live the rest of my days and rented a house in the area for 2 years while I searched for what I wanted with a good hydro source being highly desirable.        But as most of us know good hydro sites are rare, especially considering the requirement to bring an 18 wheeler in for the business occasionally and a desire not to spend every penny I had (need to save for retirement).

After 2 years searching I found a beautiful patch of 10 acres with no neighbor's houses in sight (nearest neighbor is 300+ yds away).       House is on a bit of a rise with fields extending at least 200 yds in all directions so fantastic sunsets with two 2400 sf buildings for my business with a huge parking area for trucks.     A nice farmhouse with a large 3 car garage and an additional 400 sf room (old garage that was enclosed but not heated) I call the junk room and is perfect for little projects.      1100 sf of deck space means plenty of room to watch the deer and sunsets from.      But sadly no water.       Still, after 2 years of looking I had to buy it. 

But if I ever win the lottery I'm buying that 60 acre mill site 40 miles North of here.       800 gpm  with 18' of head.