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Old 18-12-2020, 09:05   #16
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Re: Thoughts on a viable and MARKETABLE Electric Drive Train

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On a similar note I think the NEEL 43 has a lot of potential. Only a single motor needed like the gemini, 3 (6000lb) ton pay load all deep down in a centralised storage area. And a fairly light performance oriented design. Although you would probably always try to motor sail to get as much of the windward Ama out of the water to reduce wetted surface while motoring.
I think the idea would apply to a lot of cruising boats...even a lot of monohulls (though likely and inboard electric drive if the hull was originally designed for inboard). Even twin engine boats might work if you run the numbers.

I chose a Gemini as we had one and I have a good feel for power demand relative to speed and the weights that can reasonably be handled.

I keep wanting to loop back to the idea that it's designing to a "use case" and that "use case" is consistent with common new boat buyers expectations.

While they make great magazine articles and the technology can be impressive (when it works), very few new boat buyers pick up a 50ft catamaran capable of average speeds in the teens and immediately head offshore as the primary use. So when you see stuff like the Cornell boat, there really isn't a big market for that boat even if it was successful.

On the other hand 30-40ft boats at a much more reasonable cost and geared towards weekend or coastal cruising...the buyers market is much bigger. You could probably scale it up to 50ft boats (which most new ones still wind up weekend cruising not ocean crossing)...I just don't have as good of a feel for their power needs but you can also throw more money at the system because you are replacing 2 50-75hp diesels and you have much more payload capacity if it does increase weight a bit.

A big part was I wanted to avoid magical thinking regarding electric power. I'm trying to match up the power and speeds from a real boat. Undersell and Over Deliver kind of approach when most electric proponents are pushing Oversell and Under Deliver. If it does better in real life, buyers will brag it up and you will see real life tests confirming the claims. Also it will undercut those claiming it's impossible because the numbers make sense.
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Old 18-12-2020, 09:13   #17
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Re: Thoughts on a viable and MARKETABLE Electric Drive Train

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I want to start by saying I encourage meaningful and technical debate on the proposed drive train. If I made a mistake in assumptions or calculations, the goal is not to shut down discussion.r.
This was very well thought through. Sounds like it could be a pretty cool science experiment.

When I see stuff on forums I question where the "electric propulsion" market is heading. Have the manufacturers strayed from the real intent of EP which was to move our boats. Why suddenly does an EP boat need a massive battery bank, solar panels stem to stern so we can operate electric ranges, ovens & air conditioning. I'll admit I live in vacuum but this approach to power all this additional stuff has failure written all over it, at the moment anyway. We should be concentrating on the propulsion aspect first. Even NASA orbited the moon a few times before they walked on it.
Just saying...
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Old 18-12-2020, 09:18   #18
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Re: Thoughts on a viable and MARKETABLE Electric Drive Train

Anyone have a good feel for a lithium battery bank per KWH of storage? I see articles about cars getting close to $100/KWH which would be about $4k for a 40kwh battery bank but a boat builder isn't likely to get the same price point as a large auto manufacturer plus the form factor may be different.
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Old 18-12-2020, 09:37   #19
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Re: Thoughts on a viable and MARKETABLE Electric Drive Train

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This was very well thought through. Sounds like it could be a pretty cool science experiment.

When I see stuff on forums I question where the "electric propulsion" market is heading. Have the manufacturers strayed from the real intent of EP which was to move our boats. Why suddenly does an EP boat need a massive battery bank, solar panels stem to stern so we can operate electric ranges, ovens & air conditioning. I'll admit I live in vacuum but this approach to power all this additional stuff has failure written all over it, at the moment anyway. We should be concentrating on the propulsion aspect first. Even NASA orbited the moon a few times before they walked on it.
Just saying...
Most of the EP boats we hear about are more "science experiment" than viable for production. The idea here was to talk about something viable using current technology.

If anything, I tried to be conservative in my assumptions, so it might be even better (but not double or triple like some claim). One item I noticed that should probably be added is call it 40kwh of USABLE battery bank. Obviously, dragging a bank down to 0% charge is bad for the batteries, so you wouldn't want to do that regularly but lithium can go down to 10% without harm as long as they get recharged in the near future.

I do agree it seems the EP proponents get so caught up in hype, they forget the purpose (ie: use case that applies to boats that get sold in significant numbers).

I do differ a bit in terms of running house loads. This is probably one of the biggest advantages as an EP boat is likely going to cost more. While I think we can make it so the loss in speed/range small for a typical buyer, so other than eco street cred why would a buyer spend the extra money. A battery pack big enough to provide meaningful propulsion can also handle full house loads without cranking up the generator which means air/con while at anchor is a viable thing when anchoring out for the weekend. I would argue most weekend cruisers dropping hundreds of thousands on a new boat expect to be comfortable when they go to bed...even if at anchor, so I think it's a reasonable assumption.
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Old 18-12-2020, 09:51   #20
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Re: Thoughts on a viable and MARKETABLE Electric Drive Train

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So for a 35' sailboat you could motor from LA to Avalon on Catalina island at about 6.5kt. If there was a dock with power there you could recharge overnight or more likely in 36hr and then return to LA at the same speed.
If wishes were horses... There ain't no, nada, zip, docks on Catalina, with or without power. Avalon has to generate it's own power, and all 1200 golf carts are gas powered.
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Old 18-12-2020, 09:54   #21
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Re: Thoughts on a viable and MARKETABLE Electric Drive Train

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If wishes were horses... There ain't no, nada, zip, docks on Catalina, with or without power. Avalon has to generate it's own power, and all 1200 golf carts are gas powered.
That’s why I used the word “if”.
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Old 18-12-2020, 10:07   #22
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Re: Thoughts on a viable and MARKETABLE Electric Drive Train

A 40 KW, 48 volt lithium bank discharged to 10% DOD, I could run my 28' boat 36 hours @ 4 knots, maybe 7 hours at 6 knots.
I have no idea how I'd recharge the bank truth be told. I don't have that kind of real estate for panels.
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Old 18-12-2020, 10:11   #23
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Re: Thoughts on a viable and MARKETABLE Electric Drive Train

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If wishes were horses... There ain't no, nada, zip, docks on Catalina, with or without power. Avalon has to generate it's own power, and all 1200 golf carts are gas powered.
LA to Catalina can be done under battery alone. If you get any wind, you won't have to start the generator for a round trip.

Even if zero wind, you could run out on battery. Charge overnight with the generator and run back on battery (50% on shore power electric/50% on generator). So even if generator power isn't as efficient as direct diesel propulsion, it will still be a reduction in diesel consumption.

Now if you run out SanDiego to Catalina every weekend, it's not an ideal option but that's a small percentage of slow sailboat users...most doing that will be running a high speed power boat.

But on the east coast, a large percentage of cruisers will either go nearby to an anchorage for the weekend or to a nearby marina.
- If the anchorage is within an hour or two, you can do that under all battery power. It's just a question of how much the house loads will be.
- If you go to another marina, you can charge from shore power overnight. That gives you a 4 hour range.
- Day sailing, it's a total non-issue as speed is rarely a concern and you can always throttle back if the wind doesn't work to extend the hours.
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Old 18-12-2020, 10:15   #24
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Re: Thoughts on a viable and MARKETABLE Electric Drive Train

Here's a great YouTube sailing couple channel who have done a ton of long distance cruising on an all-electric boat. The link is to a video of theirs that goes into detail on their old DIY electric drive, and the new commercial saildrive unit they are installing.
https://youtu.be/GoD-j9Dy6xQ
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Old 18-12-2020, 10:16   #25
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Re: Thoughts on a viable and MARKETABLE Electric Drive Train

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A 40 KW, 48 volt lithium bank discharged to 10% DOD, I could run my 28' boat 36 hours @ 4 knots, maybe 7 hours at 6 knots.
I have no idea how I'd recharge the bank truth be told. I don't have that kind of real estate for panels.
I was going a little conservative on power demand...because I want something that is viable. 10kw for 6.5kt is probably a little high on the KW estimate (I did miss the 10% reserve which I agree with adding).

4 kts on our Gemini is just a hair over idle speed, so if you are just out for a sunset cruise to no where, you can go for a heck of a long time but to actually get somewhere, most buyers aren't going to accept that...but in a pinch or for an unusual passage, it's certainly doable.

The intent was for your typical weekend cruiser where the boat lives at the marina, so shore power would do the bulk of the battery charging. I almost wish I had skipped the solar comment as at best it's a supplemental addition and I didn't include it as part of the propulsion calculations.
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Old 18-12-2020, 10:34   #26
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Re: Thoughts on a viable and MARKETABLE Electric Drive Train

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I was going a little conservative on power demand...because I want something that is viable. 10kw for 6.5kt is probably a little high on the KW estimate (I did miss the 10% reserve which I agree with adding).
.
Based upon my boat with a 10kw drive I would say your 10kw number @ 48v, 6.5 knots is pretty spot on. That's one of the big issues with electric. You can putt along conservatively for quite awhile but once you hammer down, the stored fuel depletes rather quickly.
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Old 18-12-2020, 10:44   #27
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Re: Thoughts on a viable and MARKETABLE Electric Drive Train

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Based upon my boat with a 10kw drive I would say your 10kw number @ 48v, 6.5 knots is pretty spot on. That's one of the big issues with electric. You can putt along conservatively for quite awhile but once you hammer down, the stored fuel depletes rather quickly.
Yep, and for most people 6.5kt cruise speed is already putting along conservatively. Certainly when you look at new boat buyers. So talk about cruise speeds of 3-4kts are a non-starter for the sales team.

That's why I set it up to allow 4hrs at cruise speed and 2hrs with the hammer down (for basically a little over 1kt extra over cruise speed...we could do 7.8kt flat out but pretty much never did except 2-3 times in 10,000miles)

And of course, for longer runs, slow speeds are even more difficult to sell, so with the 5kw generator running, you could keep the 6.5kt cruise speed for 8hrs.
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Old 18-12-2020, 10:46   #28
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Re: Thoughts on a viable and MARKETABLE Electric Drive Train

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Originally Posted by misfits View Post
A 40 KW, 48 volt lithium bank discharged to 10% DOD, I could run my 28' boat 36 hours @ 4 knots, maybe 7 hours at 6 knots.
I have no idea how I'd recharge the bank truth be told. I don't have that kind of real estate for panels.
40kWhr battery is about 600lb plus about 100lb for motor, cabling, shore charger and controller. 700lb total.
If you boat is currently propelled by an outboard that’s a 100lb motor and maybe another 100lb fuel.
If you have an inboard you are probably looking at 150-200lb motor plus 100lb fuel.

Adding 400lb to the dry weight would be tough and you might have to sacrifice significant storage space to do so. I bet you could get 25kWhr on board though in the existing engine compartment. Would drop battery weight to about 375 saving about 225lb.

Recharging would be plug-in overnight; wait a long time using installed solar and maybe some wind turbine or wait a somewhat less long time using installed solar, wind and extra panels that are pulled out when becalmed or at anchor. Extra panels could use a tracking mount.
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Old 18-12-2020, 11:22   #29
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Re: Thoughts on a viable and MARKETABLE Electric Drive Train

I'm interested in how you're calculating CO2 reductions?

The electricity is generated somewhere.
Is this all wind/solar power generation?


The eco-cred calc seems suspect...
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Old 18-12-2020, 12:05   #30
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Re: Thoughts on a viable and MARKETABLE Electric Drive Train

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40kWhr battery is about 600lb plus about 100lb for motor, cabling, shore charger and controller. 700lb total.
If you boat is currently propelled by an outboard that’s a 100lb motor and maybe another 100lb fuel.
If you have an inboard you are probably looking at 150-200lb motor plus 100lb fuel.

Adding 400lb to the dry weight would be tough and you might have to sacrifice significant storage space to do so. I bet you could get 25kWhr on board though in the existing engine compartment. Would drop battery weight to about 375 saving about 225lb.

Recharging would be plug-in overnight; wait a long time using installed solar and maybe some wind turbine or wait a somewhat less long time using installed solar, wind and extra panels that are pulled out when becalmed or at anchor. Extra panels could use a tracking mount.
Already went thru this in the original post:
- 25hp 4 stroke outboard is 160lb.
- 2 - 18 gal fuel tanks full about 300lb
- 2 - BBQ size propane tanks 80lb
- 4 - 6V Golf Cart Batteries 260lb.

That's about 800lb eliminated but close enough to call it a wash if not a slight decrease.

Recharging is assumed to be shore power during the week most of the time with occasional generator use if trying to cover a lot of miles on multiple days.

A small solar array (maybe 750w) could supplement but really isn't a primary source for propulsion power unless you are only using the boat once every couple weeks. It would mostly be useful if at anchor for multiple days to cover house loads.
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