Before my friends and I start this project I thought it would be a good idea to ask you all so we don't try and reinvent the wheel.

Has any tried to water cool batteries? We have come up with 3 ideas on how it might work. On all 3 the cool system would stay on the battery and have to be connected be each use.

Please take a look and let me know what you think.

It is always great to try to solve problems you have with your own invention. I'm assuming your batteries get excessively hot? If so cooling them is not going to lower there internal resistance. If you were to buy decent batteries that have a low internal resistance they are less prone to getting hot with the same setup and will provide more current if you were to upgrade the motor.

Ryan

My first question is - why do you want to do this? Modern NiMH cells deliver more and more power the hotter they get, up to cell damage at ca. 150-160F. If your cells are getting that hot, then perhaps the better solution is to use a milder setup. Even the very best record-holding race packs will get too hot if the amp draw is too high or the run time is too long.

OTOH if you are running your boat at moderate speeds for a long run time then I can see advantages to cooling the pack. Heat buildup is cumulative, so even moderate amp draw can eventually lead to excessive heat in the cells. In this case some cell cooling would be a help.

If you are running your boat for only 2 minutes and the cells are too hot, water cooling won't do a lot for you. The cells are heating up fast from the inside, and you're cooling just the exterior in a rather inefficient manner. This will give some reduction in the internal temperature, but damage can still occur and I'm not certain it would be worth it....but I do not want to discourage you!

The best cell water cooling I've ever seen was on a race hydro which placed the cells outside the boat. When the boat was off plane the cells were in the water, when on plane they were above the surface. This gave great cooling and with NiCad cells might have helped extend their life - those cells had high internal resistance so they got hot easily. This is not a practical method today.

Fluid is right (naturally),

Modern NiMH need to be run warm off the charger, or the performance will suffer.

I once had a cooling system on a set of NiCad batteries, connected in-line; over the shrinking tube was a thin tube (grp), marginally larger then the batteries, both ends closed with silicon and a tube feeding water during the run.
On a 12 cell boat this was a major hassle with all the tubing required.

The cells never got hot, but it didn't extend the life span either.

Haven't used it since I went to run the NiMH.

Regards, Jan.