Hi John From experience batteries mostly get hot when charged at a high rate of charge When racing we would charge at about 5 amps (they would then get hot but when charged at 2 amps warm but never hot .

So check the charge rate first ,secondly I do not charge batteries near water ,they do not mix.

A final thought why not use a fan to help reduce heat , a pp9 and a simple rig should suffice ,save on buying extra batteries and use a used battery to drive a fan Good luck Michael

Is it worth mentioning that they WILL get warm once fully charged, and left on charge, as the excess charge is turned to heat?? Does not apply to clever auto charges of course. BUT my batts get reasonably warm with a clever charger, before it finishes.

Ashley

I have been charging NiCads and NiMH batteries inside my small Lindberg boats for over 20 years. Never a heating problem, but then I do charge at a low rate, lower than the 10 hour rate. Thinking about it, with modern higher capacity cells, probably nearer the 24 hour rate.

John

I have a brand new one of those Accucel 6 chargers with all leads and box sitting in my workshop doing nothing (since I treated myself to an X200). PM me if you're interested – and it won't be as much as the one from Hobby King. I think I even went onto the website and printed out the instructions, but there are several good videos on YouTube showing how to use it.
I would not use 6 cells in this model. That's 7.2v nominal (or as much as 9v fully charged) and will almost certainly blow up your receiver, speed controller, servo, main drive motor and pretty much anything else connected to it. You need just four AA cells (4.8v) mounted 2 x 2 along the bottom of the hull under the hatch. The prototype Puffer was fitted with all ACTion gear, because I designed it for the late Craig Talbot to show off his (then) new micro-sized speed controller, engine sound unit and dual switcher.

The picture shows my prototype fitted with P68A ESC, P64A Puffer Steam Engine Sound with 35mm flat speaker, 2 x P69 Switchers (smoke, whistle and lights) and Hitec HS55 servo for steering. A Hitec 40MHz "Feather" Rx was used and the whole lot powered by four 1600 mAh AA NiMH cells. The electronics fitted onto a styrene platform with the battery pack directly underneath. No extra ballast was required.

Dave M

Nicely made, sir. I knew that some clever folk would take far more care with the detail and weathering than I did. It's a very pretty picture.
You're right in that the MTroniks 10A ESC will supply 5v to the receiver via its BEC, but I'm surprised that the solar motor doesn't overheat on 7.2v – it's only rated to 5v! I guess if you don't hold the stick at full throttle then it won't upset the motor too much. The set-up which I used runs everything unregulated at the voltage of the battery pack, hence limiting it to 4 cells.
DM