Hi Jim,
There have been many conversions done on boats of that size with good results. I think you're on the right track.
While I don't consider myself an expert, I have done a couple conversions which have given me a sense of what works, so I'll take a shot at your questions. There are some more knowledgeable folks on this forum, so I'm sure you'll get plenty of good advice.
- A 36V system will work, but higher voltage will be more efficient because amp draw will be less for any given power setting.
Also, due to the way batteries lose capacity as amp draw increases, a single 200AH battery bank should give better range than two 100AH ones used one after the other.
In general it's good to keep the amp draw low in proportion to the battery capacity. Do this by increasing voltage or using bigger batteries (or both).
If you want to go with a 6-battery system, consider going to 72V in a single string, or go with a string of six 6V golf car batteries at 36V. They will handle the higher amp draw much better than your typical 12V group 31 type.
I consider about 35 or 40A to be about the max continuous draw for 12V group 31 batteries, and about 70 or 80A for 6V golf car batteries.
Not sure what kind of range you're expecting, but a couple hours at close to hull speed is easily attainable with the kind of setup we're talking about. Slow down a bit and range increases dramatically.
- To get any kind of efficiency, you probably will want gear reduction on a boat that size.
- Chain vs. Belt... I used chain on my first two installations because it's cheap and I could afford a bunch of sprockets to experiment with. On the down side, chain is noisy and messy. You can get "oil-less" chain, but it's still noisy. Definitely go with belt.
- Mounts... Shop around. I'm sure you can get a mount for a lot less than $4K. Electric Yacht (electricyacht.
I must confess I'm partial to Electric Yacht as my brother Scott owns the company and I am familiar with his systems. I have no financial interest in his company, so please don't beat me up for posting a plug.
Anyhow, good luck with the project if you decide to press ahead with it. I think you'll be very pleased with the results once you get it all dialed in.
Jim McMillan
--- In electricboats@
>
> I am considering repowering (Atomic 4) my 26' 6000lbs sailboat with a Mars PMAC. I will be using the boat for costal cruising on Lake Erie, the need for power would be getting in and out of the docks. I am thinking a Mars PMAC with 250A Sevcon programable regen controller, 2 banks of 3 batteries running at 36 volts. using a direct drive and the 50volt/rpn constant that would max out at 1800 RPM.
>
> Even though I have a good understanding of electrics and a basic understanding of electronics, I have an above average mechanical ability as I have repaired everything from cars to hospital ventilators.
>
> Questions:
> Will a 36 volt system work?
> Do I need a gear reduction?
> What are the advantages of timing belt over chain?
> Does anybody make a motor mount that costs less than $4000?
> What am I missing?
>
> Thanks for your help
> jim
>
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