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Old 23-12-2018, 09:14   #16
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Re: PSC34 electric propulsion conversion progress

Keep in mind that the 12kw motor rating is probably for its max rated voltage, which is likely 96V. And 12kw out of a 48v bank would be about 250 amps. Just sayin. Nevertheless the motor should be sufficient for your intended usage.



It is nice to plan for switching to a bigger prop, but you may find that you just can't swing a bigger prop. You need a couple inches clearance with the hull. But cleaning the one you got will improve performance a LOT. You can do it in the water, in minutes. At least knock the barnies off. With EP, you will find yourself more concerned with incremental improvements in efficiency such as clean prop and hull.



FWIW my bank is also 48v on my electric boat, and consists of 8 GC-2 golf cart batteries from Sams CLub, now I think 4 years old, still going strong, at a cost of $85/each, giving me a 10.56kwhr bank. I am quite pleased with my return on that purchase. I also eliminated the old 12v house bank. One bilge pump, the higher one, is connected directly to the first two batteries. The second, lower one, and all other 12v loads, come from a DC/DC converter.


You will appreciate the improvement in usability and maneuverability of the EP system. Instant on, instant torque, near instant reversing, no startup sequence or lucky charms or incantations or prayers when you hit a start button. No minimum idle speed!!! If you want to ghost into your slip at 50 RPM, you can. No more bumping in and out of gear at 700 RPM.


Regen really doesn't offer much until you are regularly achieving double digit speeds. On my boat, it was very small indeed, I think I was getting around 140 watts or so, max. Not enough to be concerned with. Better to just let the prop windmill with no load. An old school two blade sailboat prop, locked down in the vertical position, would also be good. The original folding prop was too small but a bigger one might have been okay. Anyway prop drag will never slow you more than about half a knot, on the typical sailboat. If you were in a hurry, you would have a different sort of boat altogether, I am thinking.


Another advantage to EP is "power tacking". Some boats are very stubborn tackers, particularly when you don't have crew to handle the headsails. In this day and age of fin keels and boats that pirouette on the head of a pin, a whole new generation exists that think wearing ship instead of tacking through the wind is comical and lubberly. And it is a PITA, too. So you flip one switch, turn one knob, and instantly you have mechanical propulsion to force her across onto the other tack. Even singlehanded full keelers are very tackable if you give it a little push with the prop. Would you really want to start a diesel for every tack? No? I didn't think so. Nobody does, AFAIK.



The portable generator is a common means of extending the range of an e-boat. The Honda 2k is very popular. I have a 2k Ryobi that is very light and portable, has bluetooth connectivity, starts on the first or second pull, sips gas, and so far, knock on wood, has been very dependable. I use a Variac connected to the 120v output, to feed a welding rectifier for charging batteries while underway on battery power. Requires careful monitoring, yeah, but it is a cheap solution. The variac and rectifier together were only a couple hundred bucks, at most. The Ryobi lunchbox genny was on sale for $500-something, I think, at Home Depot. This is NOT an efficient way to run an EP system, but it will get you home if you overextend your battery use. It will never be needed for day sails or weekenders, for just ins and outs, anyway. Shore power will take care of that. Cheap insurance though. And if you have gasoline aboard, may as well hang a little Tohatsu long shaft outboard on the stern, for additional backup.
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Old 23-12-2018, 18:49   #17
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Re: PSC34 electric propulsion conversion progress

Thanks Growley. Your conversion is one that encourages me as you seem to have success by realizing the benefits of EP and also the limitations. I think a lot of the people who have been disappointed with professional conversions were expecting too much out of their system or were sold on some fantasy "this electric motor will get your sailboat on a plane for 10 hours at full throttle"

When you realize people still use a sculling oar, which only produces about the equivalent thrust of *maybe* 100 watts going into a good brushless EP system, you realize even a 10kwh bank would have over 2 days of sculling power running 24 hours a day and still stay above 50%. Show me someone who could scull for 48 hours straight!

Still, the generator, as you say, would be good backup, especially if we are already going to have an outboard for the runabout. I do not know if there is a reasonable way to get propulsion from an outboard mounted on a PSC34...the canoe stern is a bit of a head scratcher how to get some mount easily on there.

The controller or motor can be swapped out in minutes and carrying spares is neither heavy or really that expensive. We plan on two independent battery banks, each switched and fused (300A fuses with Gigavac switches). The first bank is already in place, eight Lifeline GPL31XT 12V 125AH batteries wired up as 48V @ 250AH. The second bank may end up being eight of the Trojan Trillium LFP 12V batteries 92AH, giving 48V at 184AH. I can take the Lifelines down to 50% and get maybe 1000 cycles and the Trilliums can supposedly go 80% DoD and get 5000 cycles. This would give us a usable capacity of 13kwh and a bit more than that in an extreme emergency. A couple hours of motoring at hull speed in reasonable seas and a decent range at 4 knots (a super long range if just using it to tack as you say or to point a little closer to the wind).
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Old 23-12-2018, 19:33   #18
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Re: PSC34 electric propulsion conversion progress

How many HP was the diesel that you removed, and how fast did it move the boat?
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Old 23-12-2018, 19:50   #19
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Re: PSC34 electric propulsion conversion progress

Quote:
Originally Posted by KTP View Post
I do not know if there is a reasonable way to get propulsion from an outboard mounted on a PSC34...the canoe stern is a bit of a head scratcher how to get some mount easily on there.
I have a removable mount for an outboard motor on my PSC34. I don't have pictures, but here is a rough description. I made it years ago as a "get home device" when we were having some serious engine problems.

I have the closed stern rail and a midship boarding ladder.

A piece of 4" aluminum channel extends vertically from the lower bar of the stern rail to near the water surface. It is attached to the lower bar and to the U-bolt towing eye in the aft chain plate. The outboard engine mount extends aft from the lower end of the aluminum channel.

While my attachment to the lower rail of the stern rail is more complicated, U-bolts through the channel web should be fine. The towing U-bolt passes through a rectangular hole in the web of the channel and a wedge passes through the U-bolt pining the channel in place. The engine mount bolts to the rear facing flanges of the aluminum channel and looks like this.



Other than testing it, it has never been used.

Bill
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Old 23-12-2018, 21:17   #20
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Re: PSC34 electric propulsion conversion progress

Quote:
Originally Posted by KTP View Post
Thanks Growley. Your conversion is one that encourages me as you seem to have success by realizing the benefits of EP and also the limitations. I think a lot of the people who have been disappointed with professional conversions were expecting too much out of their system or were sold on some fantasy "this electric motor will get your sailboat on a plane for 10 hours at full throttle"

When you realize people still use a sculling oar, which only produces about the equivalent thrust of *maybe* 100 watts going into a good brushless EP system, you realize even a 10kwh bank would have over 2 days of sculling power running 24 hours a day and still stay above 50%. Show me someone who could scull for 48 hours straight!

Still, the generator, as you say, would be good backup, especially if we are already going to have an outboard for the runabout. I do not know if there is a reasonable way to get propulsion from an outboard mounted on a PSC34...the canoe stern is a bit of a head scratcher how to get some mount easily on there.

The controller or motor can be swapped out in minutes and carrying spares is neither heavy or really that expensive. We plan on two independent battery banks, each switched and fused (300A fuses with Gigavac switches). The first bank is already in place, eight Lifeline GPL31XT 12V 125AH batteries wired up as 48V @ 250AH. The second bank may end up being eight of the Trojan Trillium LFP 12V batteries 92AH, giving 48V at 184AH. I can take the Lifelines down to 50% and get maybe 1000 cycles and the Trilliums can supposedly go 80% DoD and get 5000 cycles. This would give us a usable capacity of 13kwh and a bit more than that in an extreme emergency. A couple hours of motoring at hull speed in reasonable seas and a decent range at 4 knots (a super long range if just using it to tack as you say or to point a little closer to the wind).

All true, but I suggest going with a series bank, or two series banks, whatever. There are potential problems in connecting batteries in parallel, particularly when they might be discharged vigorously at times. If you need more storage, use bigger batteries, in series, is my suggestion. 6v batteries are a good option, as are single cells. For the same weight per block, you get more amp/hours. You just have more blocks in series for the same voltage at higher capacity with no paralleling.



I actually like the idea of a reserve bank. Some expert type guys scream in indignation at the very idea, and not without reason, but it could be nice to find yourself in an "oh crap, my batteries are down to 20%!" situation and be able to turn it into a "I am quite prepared for this... I have ANOTHER bank that is fully charged, to get my little craft safely home" moment. I was planning on adding another bank of 220ah golf cart batteries to Mr Wiggles but all projects on that boat are currently on the back burner while I fit out Brute Force.
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Old 02-01-2019, 11:23   #21
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Re: PSC34 electric propulsion conversion progress

I hope you have been able now to test out your system, and I think you could have some regeneration with your 3/1 reduction. For every turn of the propeller while sailing, the "motor" (alternator) does 3 turns.
It will help to start generating even when you sail not that fast, maybe 5kn.
On my boat I start generating really well from 5kn up, I also have a 3/1 reduction gear but I use a 72V system and I guess that my prop is a bit bigger.

As said before, be careful with specs on electric motors when you use them on a lower voltage they will turn slower and will need a higher amperage to produce the same amount of force and possibly overheat faster and will not have the same maximum Kw output and torque.
But lower voltage is safer to work on and easier to generate with wind and solar.

I liked the Thunderstruck motor kits but could never buy one because they refused to sell me what I wanted, now I have a similar installation at 1/3 of their price but I had to design and adapt everything to fit my needs, so my setup doesn't look that shiny.

The advantage on the other hand is that I custom made all the supports, reduction gear and thrust bearing gear with local stuff (in Ecuador) what you could find everywhere in the world and if I need to replace one of my thrust bearings I just can find it for around $10 in any car parts shop.

I still may make some modifications such as buying a 4 blade propeller. (now 3)
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Old 04-01-2019, 18:59   #22
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Re: PSC34 electric propulsion conversion progress

No, we have not gotten to take the boat out for a test run of the electric propulsion yet. Being hit with gale after gale so we decided to go ride snowmobiles instead :-)

I am hoping for a little regen but not expecting any. It would just be a pleasant surprise. We are thinking of putting on a prop which would be more efficient for the electric system and probably would produce more regen as well if regen actually does work. Probably would help some to knock the barnacles off of this prop before we take her for a test...
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Old 26-01-2019, 08:13   #23
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Re: PSC34 electric propulsion conversion progress

Just wanted to share the method we came up with for attaching the Curtis hall effect throttle control to our pedestal assembly. It involved machining down the old stainless steel throttle control lever shaft to a 0.235" square so it would directly fit inside the Curtis throttle. We also machined the shifter mount hole larger so that the keyswitch would fit in that side (don't need a shifter with EP).

Now there are no mechanical linkages. We did buy an extra throttle which we will keep in a sealed bag, but this one is potted and uses the hall effect sensors so should be fairly robust.

As a side note, we are planning to take this little milling machine with us when we start full time cruising. It fits with the accessories in two Pelican 1650 cases and is just so useful.
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Old 26-01-2019, 08:23   #24
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Re: PSC34 electric propulsion conversion progress

Nice job, I really like that machine.
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Old 06-02-2019, 18:34   #25
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Re: PSC34 electric propulsion conversion progress

Finally got a break in the constant gales and managed to take the boat out for a trial run of the electric propulsion.

We didn't go far because it was getting late in the day. I think we did only 5nm total.

Very little wind and no waves, so ideal conditions for a motor. The prop had about 8 pounds of barnacles on it, which is not exactly ideal. I hope this year to replace it with a larger prop, maybe with 5 blades, that is super efficient for propulsion and regeneration. I am not worried about drag as we could just let the motor run at 1 amp to spin the prop and eliminate any drag. I think something like a 5 blade 18 inch to 20 inch prop would really make for a efficient electric propulsion and possibly regen.

Anyway, we motored out of the marina at 50V @ 10 amps (500 watts) which pushed us along at about 2.1 kts. In the open water I saw us move at 1.1 kts at 3 amps (150 watts), 1.8kts at 8 amps (400 watts). 2.5kts at 16 amps (800 watts), 3.2 kts at 30 amps (1500 watts), and 4.5 kts at 80 amps (4000 watts). We didn't take it up past that 80 amps this first trip out because I wanted to check for leaks and things in the rudder seal stuffing we had just replaced (no leaks!)

All in all not bad. Again, very calm conditions but also our prop looks like rock candy. Stupid barnacles. I would say with our current 250AH AGM bank we could at least get 10nm in these conditions if we kept the speed around 3 to 3.5kts. If we end up going with the planned 30kWh of lithium, then our range would be around 20nm to 40nm depending on conditions and speed. Possibly a better clean prop would make a world of difference too.


edit: Oh, it was fun docking with the electric motor. Insanely easy with the instant fwd, reverse and able to go at 20rpm if you want. Very very quiet too, I could hear people talking on the dock 80 feet away. I think some people actually thought we had lost propulsion.
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Old 07-02-2019, 09:45   #26
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Re: PSC34 electric propulsion conversion progress

Congratulations. Good first trip.

Cleaning the propeller [and the bottom] will make for a very large improvement in performance and reconfiguring to a propeller of a more appropriate size and pitch to match the high torque efficiency of the motor will make for better utilization of the torque profile of your prime mover.

Do you have an efficiency map of your propulsion system [total inverter and motor efficiency]?
Do you have a graph of the power to vessel speed curve from the manufacturer of your vessel [i.e., your load profile]?

The vessel load graph will reveal your load profile and then you can determine the power requirement of different hull speeds to determine your match of optimized propeller and take full advantage of the sweet range of your propulsion system efficiency.

I suspect a higher pitch and wider diameter propeller would take better advantage of your ePropulsion system torque characteristics [assuming your motor and gearing are not oriented to high speed operation], especially given you are dealing with a slow displacement vessel. Indeed blade count is an additional metric, you could increase blade count if you are limited in diameter, but the difficulty with too many blades is that the trailing blade gets pushed into disturbed water flow from the close proximity of the leading blade when there are many radial blades. Three blades will likely be optimal given the slow advance speed through the water.

The propeller your vessel was equipped with that was powered by an internal combustion engine will not likely be optimal for your ePropulsion system.

Good luck.
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