Re: [electricboats] Silly question - Hybrid what-if'ing

Yes, power is power.

The thought was that it's relatively cheap to buy a portable generator and carry a can of gas as backup.

Looking at this a different way...

If I go with traditional 48V motors (maybe even 10Kw so that I have plenty of room to grow) - can I power those (at low power) from a DC power supply running off a portable generator?   Is it possible to buy a 2000W or even 3000W 48V DC power supply that runs off 110VAC?   This would (in theory?) allow me to run off a very small battery bank, or no battery bank at all initially.

Then there's the electrical question:  If I connect a 3000W power supply to a small lithium battery (which would be very unlikely to have exactly the same voltage - higher when charged, lower when discharged - will I blow up anything?

I'm assuming a 3000W power supply would be significantly more cost effective than trying to find a 3000W charger (which would be massive overkill, and likely damage a small battery bank).

John

On Tuesday, May 25, 2021, 09:53:32 PM CDT, Dan Pfeiffer <dan@pfeiffer.net> wrote:

Setting aside efficiency differences it still takes the same amount of power to move the boat at a given speed.  AC, DC, gasoline, diesel.  Doesn't matter.  The boat wants what the boat wants.   Higher voltage will be lower amps.   Lower voltage will be higher amps.  The watts remain the same.   The sizing of the wires may change but the power needs remain the same. 

An AC motor can indeed be used with a controller that allows for forward and reverse and all the rest.  Your battery bank challenge will remain.   It may even get larger from more losses through added inverter stages.  

The generator can also work.  For a 6 ton boat you'll need something in the neighborhood of 2000 watts to go 4 kts?   Doesn't matter where you get it or what conversions in may go through making it's way to the propeller.   If you're going to loose half of it on the way you need to start with 3200.   An AC motor will work but it won't pick up the check at lunch. 

Dan Pfeiffer

On 2021-05-25 9:19 pm, john via groups.io wrote:

 

 

This is probably a really silly question, but....

 

Is it possible to find a 120V AC motor that can be speed controlled (and maybe even reversed??) for at least a proof of concept on a boat?

 

For those of us that prefer electric motors to gas or diesel engines, but are challenged by the investment of a huge battery bank, wouldn't it be cool if we could run an AC motor off an inverter from whatever battery bank we have handy, and use a generator to supplement - or just run off the generator entirely at first?

 

We've discussed the efficiency gain of running off a higher voltage / lower current.

I'm guessing that there just isn't a suitable way to control and/or reverse an AC motor??

 

John