# Low Power AC system?



## Ziggythewiz (May 16, 2010)

The only real issue with such a system is the amps needed from the 12V battery bank. If your setup can handle 100 amps continuous you should be fine with 5 amp at 230v from an inverter.


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## Trefmawr (Aug 2, 2012)

I guess the dependency would then fall on the inverter and controller? Are there inverters available that can handle 100 amps continuous? I've seen the controllers out there do that no problem, but they run on 24v. If I increase the voltage of my battery bank my AH will be halved though. Not really a problem per sé, just less run time. 

Thanks!


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## Ziggythewiz (May 16, 2010)

It's the same runtime because you'll be pulling 50 amps @ 24V instead of 100 @ 12V


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## PStechPaul (May 1, 2012)

If you don't need variable speed control this should work. I made a backup sump pump for a friend and it uses just a large 12V battery on a charger, and a 2000W Harbor Freight inverter which seemed to run the pump motor quite well for the couple of minutes it took to drain the water when testing. I don't know how efficient it is or if there would be problems running continuously.

You can get a small three phase motor up to 1.5 HP for under $200 new and about $50 on eBay. A 2HP VFD controller might also be about $50. And you should be able to generate 250-300 VDC for the DC link by using a bridge rectifier and a couple of large capacitors. I've done it using a 350W inverter and it ran my 2HP motor but not enough to move my tractor. Here is the circuit:










You may do even better by getting a 240VAC inverter. Here's one that might work, although it's only 1000W, but really if you will only be pulling no more than 1HP it should be OK. And with 220V you would only need to connnect it directly to the single phase input of the VFD, if it's rated for that.

And if you are willing to hack it there should be an internal 300 VDC bus that can connect directly to the VFD. Not bad for $45 including shipping. I've dealt with kangdigital before, and they are mostly reliable:
http://www.ebay.com/itm/320800175307?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

I might get one myself. I'd rather run on 24 or 36 volts but I could just run my batteries in parallel. I'm looking for closer to 2HP but yet this unit is rated at 2000W peak, so it should work. What the heck. Why not. It's probably good as a standby emergency power source as long as I keep enough charged batteries around!


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## Trefmawr (Aug 2, 2012)

Would it matter for the VFD controller and the motor if the inverter was modified sine wave? I've read that pure sine wave is really only a big deal for newer electronics like plasma tvs and whatnot. 

I'm still very new at electronics so I'll have to learn about how to read that circuit chart you posted, but thank you so much for it!

This is a really big help!

Cheers~


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## Roy Von Rogers (Mar 21, 2009)

My first question is how are you planning to connect such a motor to the water hardware wise. Not sure how big of a pantoon boat you have, but I'm guessing its running outboard motor(s) right now.

There are a lot more question about what your wanting to do, but remember your working in a water enviroment, and proposing to use some letal high voltages.

Roy


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## Trefmawr (Aug 2, 2012)

It's going to be a custom pontoon design with a shaft driven inboard motor design. The motor compartments are protected against water as much as possible, similar to how an electric sailboat motor would be installed.


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## Trefmawr (Aug 2, 2012)

When the power coming in from the battery bank at 12vdc gets inverted out to 230vac, what happens to the amps? The output needs to be 3.4 amps at 230vac which equals 782 watts (1hp). Would that mean that the amps coming out of the battery bank would be 65.1a? (782w / 12vdc = 65.16a)

If that's the case, would I be better off using a DC system rated at 24v and 24amps?


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## Roy Von Rogers (Mar 21, 2009)

Yes, I think a dc system would be better. But you need to remember where your putting the motor, inside of a hull. Electric motors are no different then a gas engines, they need cooling.

You would be better off with outboard, I have seen others use the bottom off outboards and install electric on top. This would give cooling and would be much more manuverable, cause if you use an inboard motor, your steering would be rudder, and not near as manuverable.

Look at this idea just like it was an electric vehicle, use the same type motor and controllers, and voltages, as these items are readily available.

If you still insist on inboard, I would recommend a water cooled motor.

Also using lithium ion batteries is a no brainer.

Roy


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## Trefmawr (Aug 2, 2012)

Yes I had originally looked at doing an outboard conversion, mainly for the same reason: cooling. The steerin would be a bit different though as the pontoons are more like a catamaran, where the 'pontoons' continue out past the stern and now of the deck/cabin structure. With the inboard electric system I imagined, it's a dual motor system with dual rudders, so maneuverability would still be decent. Add reverse into that and you should even be able to 360 almost on spot. 

For cooling I was looking at a water cooled flow-by system that would use a water pipe wrapped around each motor. 

Right now I'm just gathering information and seeing what is possible. Thanks very much for all your input and help though! Really helping me here 

Also there will be a backup/secondary outboard motor for use when electric is no viable. 

Cheers!


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## Roy Von Rogers (Mar 21, 2009)

Trefmawr said:


> Yes I had originally looked at doing an outboard conversion, mainly for the same reason: cooling. The steerin would be a bit different though as the pontoons are more like a catamaran, where the 'pontoons' continue out past the stern and now of the deck/cabin structure. With the inboard electric system I imagined, it's a dual motor system with dual rudders, so maneuverability would still be decent. Add reverse into that and you should even be able to 360 almost on spot.
> 
> For cooling I was looking at a water cooled flow-by system that would use a water pipe wrapped around each motor.
> 
> ...


 
Just so you know, the only reason I'm giving input.....I been working (thinking) about the same project. So I'm familiar with the choices.

I'm assuming you see where I live...lol

And forget the tubing around motor...get one with a water jacket if you decide on an inboard. And I forgot, if inboard....the controller may have to be water cooled.

Roy


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## PStechPaul (May 1, 2012)

I bought 8 of these 1/8HP (1/4HP peak) 12VDC motors on eBay for $50:

















That's probably too fast for a prop, but you can make a reduction drive using timing belts and pulleys. I'm using a pair for a 24" wide electric trimmer/motor. 

I also just purchased this series wound 3900 RPM 8 in-lb 12V motor for $8:








http://www.herbach.com/Merchant2/me...AR&Product_Code=TM01MTR4476&Category_Code=MTR

I think it's also about 1/8-1/4 HP. So for a boat, and low HP, DC motors are probably best. You probably will need a speed reducer. The same company has gear motors for under $30 that should work. 

You can get motors that will work underwater. Look for well pumps. They might even work for propulsion using the water jet! 

Most are 120/240VAC. But you can probably add a GFCI to the output of the inverter so it will be fairly safe. Even 12VDC can be deadly in salt water. It won't electrocute you but it can push enough current through your muscles to immobilize them so you can't swim or climb back out of the water. 

Here's an electric JetSki:


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## Trefmawr (Aug 2, 2012)

Yeah I saw that! I'm planning on getting down to florida from the great lakes eventually, but that's a ways off! 

Depending on motor and controller temperatures, I was also thinking of fabricating a fresh air cooling duct system that has the intake up high and away from the water (with a rain guard and trap of course) and a flue of some sort. I don't really have to worry about aesthetics as it's a house boat haha!

I might gather some components and bench test them to get some hard data first before making a final decision. Have one motor, controller, and battery setup and running for a while and if it gets too hot for enclosed space, then I can just use it on my jon boat 

PStechPaul: Yeah I had also considered making a multi-motor array out of smaller, cheaper DC motors like those. Thanks for the links! More to stew over  With those kind of RPMs I would definitely be using a reducer of some sort. In my current design I have a chain driven setup that would put the RPMs in a nice range for prop use.

Also, I plan on installing as many safety features as possible (without hindering the system too much) including battery hard cut-off switches, a deadman switch (kind of like how a pwc works) and water alarms. 

Cheers


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## PStechPaul (May 1, 2012)

Just found this :


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## Trefmawr (Aug 2, 2012)

Found this while perusing ebay:

http://www.ebay.com/itm/261076537568?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

Thought I might get one on my bench test setup and see how it holds up?

Cheers

PStechPaul: Those vids are great! Also, where did you pickup those 1/8HP 12vdc motors? Can't seem to find any on ebay...


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