Hot batteries

[BBQSteve]

My batteries after a run are at almost 200 degrees. Here is my setup in a twin configuration:

Red Leopard LBP3650-B/3.5D, 86A, max, 15V max, 1300W max, 3900KV, 0.0075 internal resistance, 2.7A no load, 4 pole
Turnigy Marine 120A ESC, Constant Current: 120A, Burst Current: 240A, Resistance: .0007ohm, Battery: 2-6S Lipoly, BEC: 3A/6v, Motor Type: Sensorless Brushless, *Speed: 100,000+rpm (2 Pole)
Batteries Venom 3000mah, 7.2V, NIMH

These motors are fitted to Aquacraft EP1 motors, are water cooled and running cool. The ESCs are running cool with no water cooling. I am using soldered Dean Ultra plugs from batteries to ESC and standard crimped automotive type bullet connectors to the motor. Due to the distance from the ESC to the motor, an extension of 6 inches is added to the ESC and another extension to the motor something like this:

Battery()====ESC===[]Transom[]=====||====Motor

() = Deans Ultra [] = Automotive crimp bullets 5mm || = 5mm gold soldered connectors

All this in a 34 inch Aeromarine Titan.

Thanks for any insight.

BBQSteve

[video200]

what batteries you use on this ? how long you run for ?

[BBQSteve]

Venom 3000mah Nimh, 7.2v, haven't actually timed the run, but would guess 10 minutes. Not running WOT all the time.

[domwilson]

My first thought is that you are pulling too much current from the batteries. Try either higher capacity batteries or lipos. Maybe 4000 mah 25C or higher. The second thought would be to replace the deans with bullets. How big is the boat? You could also be running too high kv motors for your application.

[BBQSteve]

The boat is 34 inches in length and weighs, ready to run, 10 lbs.

Another interesting topic, kv rating. What is the difference in running a 3900Kv at 7.2v and a 1800Kv at 15v, besides a slight rpm difference. Forgive me, I am new to electrics.

[Doby]

The Venom batteries are bottom of the barrel for quality...thats your biggest problem.

[runzwithsizorz]

Another VA. member, AND another Titan owner. Like others have said, probably the batteries. I am in Williamsburg, and if you were within 50 miles I would bring my Titan, and some different nimh's, or lipos to try.

[BBQSteve]

Made another run today. Batteries were cooler. Yesterday, I ran the motors in the water to discharge the batteries. Probably not a good thing to do. Also found out I need more lake. Ran out of room. GPS says 21. Boat weighs 8#'s with GPS and camera.

[BBQSteve]

Runzwithsizorz, I am in Norfolk on a Lake Whitehurst canal.

[domwilson]

What size props are you running? 21 mph seems kind of low.

[Boaterguy]

the difference is amp draw, a 1000watt motor using 10 volts (for simplicity's sake) will draw 100 amps (more or less depending on load)
a lower Kv motor still rated at 1000 watts but using 20 volts (again for simplicity's sake) will draw 50 amps, the whole boat will run cooler.
Volts * Amps = Watts
lower KV motors are usually bigger and have more power to move a bigger hull

[BBQSteve]

Domwilson, I am runing stock EP 1 props right now. They measure out to about 1 inch pitch and given the formula for calculating mph using 80% efficiency, it is just about right on the money. This is a fun boat not a SAW, keep this in mind.

Boaterguy, yes that is true assuming the max wattage of a hypothetical motor is 1000 watts. Don't need to be simple, I understand Ohm's and Kirchoff's Laws. Just for giggles, these motors have capacitance, reluctance, impedance and inductance, as well as internal wire resistance, (just for simplicity sake.) The fact that lower Kv motors are bigger (larger wire) and have more power (fewer turns) is good info. Is there somewhere to learn more about how these motors are rated and spec'd?

Runswithsizorz, would love to get up with you sometime. I'm 45 minutes from Williamsburg after summer when tunnel traffic settles. I am retired and free most days.

[BBQSteve]

I found this to be an extremely well written article with great information in it. Probably deserves a sticky here.

http://www.rcuniverse.com/forum/m_3320764/anchors_3320764/mpage_1/key_/anchor/tm.htm#3320764