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Old 10-04-2020, 11:37   #16
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Re: Highfield 310 CL with ePropulsion Navy 6?

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Originally Posted by alansmith View Post
Aybab, please see if you can find the posts about fellas who talk about what the “real conversion” of going from gas to electric really ends up at. I totally understand where you are coming from with a hundred lbs outboard.

Just a thought. Sometimes the choice of a dingy will make a huge difference in how much power you need to plane it. For example a porta-bote at 10 foot could plane very nicely with a 6 hp outboard. You can pick up used Porta bote for under 1k and stores quite nicely.

I just seem to remember e motors being compared to gas outboards and fellas saying it ain’t what you think.
Do you have something that would help me narrow the search for the post you mention? Searching for "real conversion gas electric outboard" returned hundreds of results.

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Originally Posted by Steve_C View Post
Or get two of the electric outboards

Then you could get on a plane You would need a bigger battery tho!
Hehe I did entertain the idea. Would just have to handle the pesky problem of the prop blades hitting each other. I guess I could just try it out and see what happens..!

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Originally Posted by valhalla360 View Post
Just because it can handle a 20hp, doesn't mean you need 20hp. Unless you are heavily loaded, I would expect a 9.9 to get that dingy on plane.

Even a 15hp doesn't add much over a 9.9...for Merc it goes from 84lb to 99lb and you can pick one up for $2700...Plus if it's only for a couple years, if you take care of it, you can probably sell it for better than 75% of the original price...I wouldn't count on that with an oddball electric system.

If you just want to an electric motor...get one but comparing to a 20hp is apples & oranges.
It is apples to oranges, and bunch of tradeoffs: that's precisely why it's hard to decide on.

We'll use the dink + outboard for more than 2y, but I'm trying to be realistic about my expected usage - I'm not going to size my dinghy as if I was cruising remote South Pacific lagoons within the next 2y. When we get there, changing our outboard (if needed) will probably not be a big deal.
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Old 10-04-2020, 11:38   #17
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Re: Highfield 310 CL with ePropulsion Navy 6?

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Originally Posted by joelhemington View Post
Those E propulsion units are very highly rated. Should be fine for just casual dingy rides especially in marinas where you don't want too much wake. That said, I'd also have a 15hp outboard locked on the rail just in case you need something serious outside the marina.
Sounds fair. I guess I could always get that extra outboard if and when the need arises.
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Old 15-04-2020, 15:17   #18
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Re: Highfield 310 CL with ePropulsion Navy 6?

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Originally Posted by aybabtme View Post
With the inverter. The mothership has enough installed power generation and power capacity to replenish, and there's space for more.
The batteries are going to weigh than the motor. 6 Kilowatts of lead acid going to weigh two motors or more and Agm to be safe, Battery cost $4000 plus, here in Australia. The tender will need to be permanently in the water. Electric stowable tenders need to be small "Motor and boat"
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Old 15-04-2020, 15:47   #19
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Re: Highfield 310 CL with ePropulsion Navy 6?

How are you going to charge the batteries?

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Originally Posted by aybabtme View Post
With the inverter. The mothership has enough installed power generation and power capacity to replenish, and there's space for more.
Hmmmm... this is always the buggaboo of the cruising sailor who wants an electric outboard. They soon find that the "hassle of getting gasoline" pales in camparision to the hassle of getting all those electrons.

It seems to me you might want to look at this aspect a bit more closely.

You say the outboard is rated at 6kW, and you'll have have a battery big enough to run at full power for an hour, so the battery stores (at least) 6kW-hrs of energy. That's 500 Amp-hrs out of a 12 volts system (actually a good bit more, since we are assuming 100% efficiency all the way through).

I don't know what your expectations are. Do you expect to recharge the dinghy battery overnight? Over a weekend? A week? How long will it take you to generate 500 Amp-hrs of 12 volt energy above and beyond your normal house use?

Have you run these numbers? Did I slip a decimal point somewhere? It doesn't look practical on a 37 foot boat.
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Old 15-04-2020, 16:22   #20
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Re: Highfield 310 CL with ePropulsion Navy 6?

Yeah it takes a lot of watt-hours. I don't expect to discharge it fully every day, probably once a week? I have a lot of ways left to add to my energy generation capability, and I produce 4kWh a day right now in April, with the current 915W array using second hand, 10yo 305W panels that I could upgrade for newer, more efficient technology (same form factor now comes in 375W). I'm working on also adding more surface area, with extra panels on the dodger/bimini, and I haven't yet upgraded my alternator. Our house load is about 1.4kWh per day. All in all, I believe I should be able to produce in excess of 7kWh a day with just solar, I think that's reasonable.

And I'm curious to try and put a tiny solar panel on the dinghy itself, to maybe slowly charge the thing up when it's floating, at a dock or being towed. It probably wouldn't account for anything significant, but it could be fun to try and who knows, maybe it can recharge enough to cover a small roundtrip ride to the beach?

In the worst case, assuming no solar at all, I could just do an alternator upgrade and recharge the dinghy this way, when needed. Also, these days, we're using the boat on the weekend only, so we could plug the mothership at the marina during the week to replenish everything.

At this point, I think it's an idea worth investigating. My brain is so obsessed with the idea, I'll probably try it out and I guess I can be the guinea pig for everyone here. I've heard of dinghies bigger than mine running with a Navy 6, so I think the propulsive power side of thing isn't gonna be an issue. The electric generation side: it might turn out underwhelming, but I'm sure it won't be downright bad. In which case I'll have overpaid to do an experiment and satisfy my curiosity.

If anyone has already done exactly this - Navy 6 on a dinghy this size, and a 6kWh battery - or very similar and it turned out bad, please let me know! So far the only negatives I've heard seem to come from people who haven't experienced it themselves.
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Old 15-04-2020, 16:30   #21
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Re: Highfield 310 CL with ePropulsion Navy 6?

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Originally Posted by peter57 View Post
The batteries are going to weigh than the motor. 6 Kilowatts of lead acid going to weigh two motors or more and Agm to be safe, Battery cost $4000 plus, here in Australia. The tender will need to be permanently in the water. Electric stowable tenders need to be small "Motor and boat"
I'm building a custom lithium bank for it, not lead acid. I'm expecting 25kg worth of cells, from my CAD design. The whole thing with the enclosure should come at maybe 30kg. It is the same weight as the engine, but less than a regular gas outboard + fuel tank, and the weight is split 50/50 between the bow and the stern of the dinghy.
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Old 15-04-2020, 16:39   #22
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Re: Highfield 310 CL with ePropulsion Navy 6?

I'd take a very close look at the power connector. On the ePropulsion website it is just dangling about and while I'd assume it has some level of ingress protection I can guarantee that with the way I use my dingy it would be wet, with salt water, a lot of the time. The idea of a 48V high amperage connector out in the open getting soaked with salt water makes me uncomfortable!
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Old 15-04-2020, 17:24   #23
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Re: Highfield 310 CL with ePropulsion Navy 6?

Quote:
Originally Posted by aybabtme View Post
With the inverter. The mothership has enough installed power generation and power capacity to replenish, and there's space for more.
Boy, you lost me there. Recharging at the dock is probably reasonable since you have the week to do it.

But putting 6000w into a 48v battery using an inverter means they have to come out of something. The solar array? I wonder how big of a helo landing deck you have up there? You would have to have a big house battery bank. AND, do you supply 110v to the charger to get 48v into the batteries? Some losses there I suspect.

Upgrading the alternator is another bigger project than maybe you are thinking. To get 500 amp/hours out of the alternator you're going to have to run it, and run it hard, for quite a while.

But I get it. You really want to do this and are prepared to sink a pile of money into it and dedicate the yacht's entire electrical system towards recharging at anchor or underway if you ever need to. Further, you are limiting yourself to never needing more than 1 hour's operation, which will often be at full throttle because you're going to be underpowered. OK, go ahead.

But the vast majority of cruisers with a 3.1 RIB have a 9.9 or a 15hp gasoline outboard, and they get a lot of utility out of the bigger engine and longer range. If you can get a good used 2-stroke, better yet, and you will be amazed at how light and convenient it is.
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Old 15-04-2020, 17:46   #24
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Re: Highfield 310 CL with ePropulsion Navy 6?

Quote:
Originally Posted by aybabtme View Post
Yeah it takes a lot of watt-hours. I don't expect to discharge it fully every day, probably once a week? I have a lot of ways left to add to my energy generation capability, and I produce 4kWh a day right now in April, with the current 915W array using second hand, 10yo 305W panels that I could upgrade for newer, more efficient technology (same form factor now comes in 375W). I'm working on also adding more surface area, with extra panels on the dodger/bimini, and I haven't yet upgraded my alternator. Our house load is about 1.4kWh per day. All in all, I believe I should be able to produce in excess of 7kWh a day with just solar, I think that's reasonable.

And I'm curious to try and put a tiny solar panel on the dinghy itself, to maybe slowly charge the thing up when it's floating, at a dock or being towed. It probably wouldn't account for anything significant, but it could be fun to try and who knows, maybe it can recharge enough to cover a small roundtrip ride to the beach?

In the worst case, assuming no solar at all, I could just do an alternator upgrade and recharge the dinghy this way, when needed. Also, these days, we're using the boat on the weekend only, so we could plug the mothership at the marina during the week to replenish everything.

At this point, I think it's an idea worth investigating. My brain is so obsessed with the idea, I'll probably try it out and I guess I can be the guinea pig for everyone here. I've heard of dinghies bigger than mine running with a Navy 6, so I think the propulsive power side of thing isn't gonna be an issue. The electric generation side: it might turn out underwhelming, but I'm sure it won't be downright bad. In which case I'll have overpaid to do an experiment and satisfy my curiosity.

If anyone has already done exactly this - Navy 6 on a dinghy this size, and a 6kWh battery - or very similar and it turned out bad, please let me know! So far the only negatives I've heard seem to come from people who haven't experienced it themselves.
If you are worried about the engine being too small, it is not. It might not plane the dinghy with a full load aboard, it will do fine with one person, and in calm water, with two.

If you are doing it for FUN, have at it! It will be a fun project. I would urge caution only if you want to use it as your cruising dinghy while actually living on the hook in remote places. It's just not practical for the way most people use dinghies while cruising. Many of us have looked at them in detail, and concluded they just are not there yet.

You see almost no electric dinghies in the permanent cruising fleet. It's not because people wouldn't like them, but it's hard to square the energy needs, range, and reliability. They are still fragile beasts compared to a standard two-stroke outboard.
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