zero-ev.co.uk
It is driving a boat propeller. Certainly lower current draw than street use since at no point will this motor be near stall condition.
Be very aware of the thermal capabilities of the LDU, they are pretty terrible. You'll derate to less than 50kW after ten minutes, some people say 35kW is all they are good for steady-state. Is that enough to push your boat at the speed you require?
Because if you go WOT with an LDU you are going to draw right at 900 amps. You may not need it but if you have selected an LDU then you should have the battery to support it, otherwise you could hurt things.
This is regardless of a custom cooling setup? I will be taking cold water in off of the lake and running it through heat exchangers. The cooling loop will also have a decent amount of fluid and should take longer to heat soak compared to a standard Tesla.
Is this why I was told the Model 3 Pack couldn't suffice?
For the most part yes, although any temp reduction of the water going in compared to the car will be a direct offset- so a small improvement to be had. The issue is not the cooling, it is getting the heat from the copper to the coolant and that is not something you can solve easily. The biggest problem of any induction motor is cooling the rotor, there is a pic on Reddit of a Tesla rotor that has reached over 400degC as it is purple color in the middle.
So say I undervolt it as a start so I am not running the full 400 volts since it is rated down to 275 I believe, that should help initially with cooling, correct? Also, most of this motors life will not be spent at WoT. Cruising Around 2500-3000rpm is where it will be sustained.
Where are you getting those numbers? I have personally seen a boat that uses a 40kw pack move up to 30knots for a range of 80+ miles. Propellers, propeller layout, inboard or outboard, overall vessel weight, and the number of motors all play a MASSIVE role in range. There is also a boat that can move up to 40 knots on a 120kw pack for 100 miles. Both are full size vessels that certainly have some weight.
The concern isn't really a stall condition. Motor current isn't the issue in battery selection, battery current is. The inverter converts battery voltage and current to lower voltage and higher current to the motor. Battery current is simply the power needed from the battery divided by the battery voltage. So determine your peak power requirement, and your energy requirement (based on range or operating time and power), and choose the battery size based on that.
This is a planing hull. Center Console planing hull to be exact. Boat weighs about 3,000 lbs. If the LDU has cooling issues and other problems etc for my application, is there another option you would recommend? I need high HP on tap if I want to get up and go, but mostly will be cruising. I would like to achieve a cruising speed of 25-30mph. And I do have ICE data, for my application they're burning about 1.5GPM at cruise and down under 1 when running. Also, a prop that cruises at 7500rpm? I'm not sure if that exists? That would be screaming for any ICE outboard. Most of these props that we use are designed to cruise at 2500-3000 max and I intend to run the motor at the same RPM for cruising. Also, if most of my heating is caused by the required torque, will my required torque not be lower since I am not driving a tire on a road but rather a propeller through water?
Most certainly not, I can agree with that
. The intention is not to carry high speed all of the time. This is not a race boat. The intention is if I want to go fast for a bit, I can. Mostly cruising is the goal.
