Electric boat outboard question

Hi guys,
I'm new to the forum. Thanks for any help in advance.
I have an electric outboard motor I use on my boat, it is a 48v motor that takes 4.8kw input at the controller, and puts out 3 kw. I run it with 12v deep cycle batteries x 4.
My question is, if I added another 12v battery to my pack to make it 60v, would I harm the motor or controller? I believe it says on the controller that it handles from 32v to 60v, but a fully charged battery pack would sit around 65v.

Thanks

Running a controller to the ragged edge of it's specs (especially voltage) isn't recommended. The parts in there are likely only rated for that max voltage, so if you actually run it at that, you risk popping the FETs or low-votlage power supply inside, etc.

Running it *above* that limit is fairly likely to pop something sooner or later (probably sooner).


What specifically are you trying to achieve?

Trying to achieve more speed

More speed in a boat that rides in the water takes a fair bit of power. I don't know that you'd get much extra speed with as little power would be added by just that voltage increase.

If it's already planing, then it's less power, but adding (at most) 1/4 more power isn't going to add much speed.


Depends also on the type of boat; hull design.

There's some other threads in the water section about various boats and problems, some of which discuss power needs for various types/speeds/etc.

I'd be happy if I could get an extra 1 mph out of it, as it does not reach planing speeds, but I would even be willing to go up to 72v for that extra speed as well.
Could I just get a different controller for it and make this possible?

Maybe, it depends on the motor's capability (and maybe what prop you're using; sometimes a different prop is needed for faster RPMs/etc.).


The motor may need extra cooling to get rid of the waste heat, especially if it's already dissipating almost 2kw of wasted power as heat now.


More likely, you'll need a bigger motor to go up to the power levels that 72v vs 48v involves.

Probably better to go brushless, too, if it's not already (brushed wastes more power as heat, and is harder on them to go higher voltage).

The motor is brushless, and water-cooled as well. So... The higher the voltage applied in that motor, the more kw wasted as heat? And the higher the temps of the motor?

Generally, yeah.

The motor has some electrical resistance, so the higher the voltage and current, the higher the power loss to heat inside.

Also, the faster it tries to turn the prop in the water, the more physical resistance it encounters, and the more power it takes to turn it, and the more of that power that is turned into heat as the resistance keeps the motor from spinning as fast as it would without a physical load on it.

It's using wheels, not props, but you can get some idea of the issues by going to http://ebikes.ca/simulator, reading the whole page so you know what everything is for and what the results mean, and then trying some different setups.


You could try looking around the web to see if anyone has already tried something similar with the same outboard system, to see what results they had. Unfortunately most people don't post up results when they start such projects, so most of the time there's questions but no answers, so I don't know how much help that will be. :/

If you're going so slowly that 1mph would be helpful to you, my guess is that you'll get better results from a chance of prop than a change of voltage. If you're turning a prop that was originally meant for a gasoline motor, it probably has much too aggressive a pitch for the power you're using now.

Turning a too-fast prop even faster isn't going to help you.

Double up on an identical unit

A 4.8/3.0 kW ? O’board doesnt sound like a shop bought unit.
Running 100A continuous from lead cells also sounds unusual ?
Can you give more details of the boat and motor, and the speed you currently get ?
I too suspect the prop may be the solution