Hi All
Last Sunday I found some boaters at my local pond. They were all Nitro, or gas weed wacker boats. So a little nervous about bringing out an electric.
While they were tuning I ran the Super H , and was pleased to see that they were interested in the speed I was getting from an electric.
I still had my share of problems though.
The boat is eating battery packs. Could only get half throttle on one run. Found a battery pack had shorted out and was dead. Another time I blew a fuse, and was dead in the water.
The ESC and motors are not over heating, but the batteries. are really getting hot.
Running the batteries in series really takes the juice out fast.
Does any one know if changing props or something that may help this problem.
I've also seen a posting on another web site that says I should have a diode on the motors to stop voltage feed back to the ESC.
Any thoughts out there?

im runnin 1500 mah in my 550 motor boat and the batterys do get hot in myne i get bout 6 mins run time but i dont get no shorts or anything maybe to much cells for the ESC but the batterys do get hot no mater what

Sound to me like you need some better batteries. Which cells are you using?
If your using sport stick packs, break them down and add heavy battery bars and quality wire. Your motor is drawing more amps then your packs can handle.

Steven Vaccaro
www.OffshoreElectrics.com

In fact, every battery pack must get hot, but all batteries equally.
Today I made run with my ECO racing boat. I use 7 cell GP 3300 Matched Pack, gold connectors, and silver battery bars. 18x2 Corally BB rebuilt racing motor and 29mm Graupner Prop. With this configuration I ran about 7min in full throttle and my battery pack was very hot. When you taking it out immediately you will burn your fingers. If one of the batteries is dead, it will boiling then.
Generally, electric boats are big power consumers and useful payload will be less than 10 minutes depending on motor and prop.
Now about diodes.
Diode is at least 9A Schottky and it purpose is to protect ESC breaking FETs against
reverse voltage and have nothing to do with battery heating.

Thanks for the replies. My battery packs are not the cheep ones. Most are 7.2V 1500mah packs, also have some 1600mah packs.
Even though I don't have a reversing ESC I think I'll add the diodes to protect the controller.
Haven't had any more issues with dead packs. May have been defective from the beginning.
Along with adding the diodes I am going to upgrade wiring to a heavy guage with more strands. Also looking at different connectors. I hope to cut down some resistance in the system.
I hope this weekend is nice so I can try the super H again.
Has anyone had an issue with the motors trashing there controller?
The first I heard about it was on the offshoreelectrics web site.
makes sense the the motors could send a feedback to the ESC.

Resistance is a important issue and counts most. If you use high resistance wiring it will melt down. Weakest part of the sysetem determines the whole system power.

This is a good explanation from the Novak Website:

Similarly, the motor in a car is like a big inductor. During the off-time at partial throttle, the motor will not allow the current to just stop. Instead, the voltage across the motor will reverse, and current will flow through the Schottky diode. If no diode is present, the current will flow through a parasitic diode built into the brake transistors. The current flows through the Schottky diode before it will flow through the brake transistor because the forward voltage drop of a Schottky diode is less than the brake transistor diode (this is why Schottky diodes are used and not other types of power diodes).

For the highest efficiency, during the off-time while the motor continues to flow current, the voltage should ideally be as close to zero as possible. One reason Novak uses an external Schottky diode is because the closer the diode is to the motor, the lower the voltage drop during this period. This is due to the voltage drop through the wires back to the speed control. This will also reduce some radio noise due to the current spike not having to travel a long distance.

This will not help the heat problem with the batteries as that is a result of the power being sucked out of them, but MAY help with heat from the ESC.
Also, if I'm not mistaken you are using an Astroflight.
When I e-mailed the company (the designer/owner replied) I was told that no diode was necessary on their controllers.
Another reason for reverse protection diodes on boats is the tendancy for the prop to spin after thottle has been released.
And as you may know, a motor without a battery attached will produce electricity when turned, which travels back up to the ESC, possibly causing harm.

Thanks for all the input.
I got the same answer from Astroflight on the need for diodes. The explanation I got was that the Opto-Isolation circuit took care of the possible feed back from the motors, and would not allow the spikes to reach the scr's.
To restate: I'm not having any problems with the motors, or ESC getting hot, they are barely getting warm when I run the boat.
Just extremely hot battery packs, and only one failure, due to a shorted cell.
The Astroflight ESC is working fine, and it's not water cooled.
I need to design a battery cooler I guess. LOL
Got the Boating bug bad now. Looking for a boat kit to work on during the winter months.
Thanks again for all the info.

It looks like all the Schottky diodes are for forward directions only - they say don't use them (at-least the few I saw) if the controller has reverse. Do they make a forward and reverse diode? They say that will help cool the ESC too - is that right?

A diode only allows voltage to flow in one direction. Its to stop voltage from back feeding into the esc. You can find a some mmore info hear http://www.offshoreelectrics.com/why_to_use_diode.htm

Steven Vaccaro
www.OffshoreElectrics.com

Also like someone metioned earlier, the batteries are being drained quicker than they like. You can try a smaller prop. Its like changing the gear ratio. Changing the wiring will also help the whole setup. If the motor is not getting hot than the batteries have to much internal resistance. You will need to upgrade.

Steven Vaccaro
www.OffshoreElectrics.com

Steve - You mention changing the wires - do you mean like go to a 14g wire from the motor to the ESC and from the battery to the ESC- please explain?

If your going to change them go all the way to 12 gauge. It like a water pipe. The larger the diameter the beter the flow.

Steven Vaccaro
www.OffshoreElectrics.com

SLOWBOAT-N - did you change the wires? what have you done and what's you update?

Haven't had a chance to change any thing yet. Been to busy.
I plan to upgrade to 12 ga. wire, with lots of strands, and shorten the "y" harness to get rid of some extra wire. Have seen some wire in a catalog that looks promissing. Almost reminds you of small car battery cable.
Some one said I should upgrade battery packs.
What kind of upgrade?
More amp hour cap. or what?
With good weather in the forcast for our area this weekend I hope to get the boat out for at least one more run before the cold hits.

Keep on boat-n All

By upgrade I would mean change to a custom pack or make your sport packs less resistant by taking them apart, changing to heavy duty battery bars and heavy gauge wire. The biggest slow down is the tamiya connectors. They steal lots of power from your motors.

Steven Vaccaro
www.OffshoreElectrics.com