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Jatar · 19-05-2019, 09:11

Quote:

Originally Posted by newhaul

Cure is 48v dc genset .
A friend did that to his 38ft mono . Only a small Fla bank and a 5k military surplus 48v dc generator.
Like this would work

[url]https://polarpower.com/products/dc-generators/8080y-40205-diesel-dc-generator/[/url

You may need 2 on the cat.

Those are too small. I'm likely going with a 20kw and a 10kw, though there are some arguments to go with just one 20kw, but I like redundancy.

**newhaul** · 19-05-2019, 09:34

Quote:

Originally Posted by Jatar

Those are too small. I'm likely going with a 20kw and a 10kw, though there are some arguments to go with just one 20kw, but I like redundancy.

I posted a new link to a bigger genset but it didn't take so here is the new link

https://polarpower.com/products/dc-g.../8220y-3tnv88/
this link is for the 15k unit.

Jatar · 19-05-2019, 10:07

Quote:

Originally Posted by newhaul

I posted a new link to a bigger genset but it didn't take so here is the new link

https://polarpower.com/products/dc-g.../8220y-3tnv88/
this link is for the 15k unit.

I am already familiar with Polarpower, however, the two I'm interested in are these:

https://polarpower.com/products/dc-g...s/8340p-40415/
https://polarpower.com/products/dc-g...rs/8220i-3ca1/

**newhaul** · 19-05-2019, 11:03

Quote:

Originally Posted by Jatar

I am already familiar with Polarpower, however, the two I'm interested in are these:

https://polarpower.com/products/dc-g...s/8340p-40415/
https://polarpower.com/products/dc-g...rs/8220i-3ca1/

those look great I just posted the one that in individually would run st e system and in tandem would reduce the overall fuel consumption .
On lower rpm 15kw and about 3/4 gph at the higher rpm 18kw at 1 gph
Would make weight distribution easier as well

Jatar · 19-05-2019, 11:16

Quote:

Originally Posted by newhaul

those look great I just posted the one that in individually would run st e system and in tandem would reduce the overall fuel consumption .
On lower rpm 15kw and about 3/4 gph at the higher rpm 18kw at 1 gph
Would make weight distribution easier as well

I originally considered that (and haven't ruled it out) but I like the idea of running only one generator and having it supply enough power to drive both motors at around 6 knots, with some power also left over to charge batteries.

The second 10 kw is there for times when I don't need to power the motors (like at anchor) but need to generate some power. I don't have to fire up a bigger generator.

In an emergency, together, the two supply enough power to run both motors at full power for as long as I have diesel fuel.

I'd love to hear counter arguments to this setup, as I have not fully decided on this yet. Right now, the three options I am considering are:

1) A 20kw plus a 10kw generator.
2) Two 15kw generators.
3) One 20kw generator (no redundancy, but reduced space needs and less initial cost, weight, and maintenance time and money).

I considered a single 30kw, but they are just too heavy.

**newhaul** · 19-05-2019, 11:40

Quote:

Originally Posted by Jatar

I originally considered that (and haven't ruled it out) but I like the idea of running only one generator and having it supply enough power to drive both motors at around 6 knots, with some power also left over to charge batteries.

The second 10 kw is there for times when I don't need to power the motors (like at anchor) but need to generate some power. I don't have to fire up a bigger generator.

In an emergency, together, the two supply enough power to run both motors at full power for as long as I have diesel fuel.

I'd love to hear counter arguments to this setup, as I have not fully decided on this yet. Right now, the three options I am considering are:

1) A 20kw plus a 10kw generator.
2) Two 15kw generators.
3) One 20kw generator (no redundancy, but reduced space needs and less initial cost, weight, and maintenance time and money).

I considered a single 30kw, but they are just too heavy.

well I'm a navy engineer so two 15kw units the o Crap redundancy aspect.
You just need a bit of extra at anchor that's what a Honda is for.

Jatar · 19-05-2019, 13:24

Quote:

Originally Posted by newhaul

well I'm a navy engineer so two 15kw units the o Crap redundancy aspect.
You just need a bit of extra at anchor that's what a Honda is for.

What does "the o Crap" mean?

**newhaul** · 19-05-2019, 13:33

Quote:

Originally Posted by Jatar

What does "the o Crap" mean?

one gen failure you would still be fully operational with the other one at max output.
That way a failure wouldn't prematurely end your cruise for repairs.

Jatar · 19-05-2019, 13:45

Quote:

Originally Posted by newhaul

one gen failure you would still be fully operational with the other one at max output.
That way a failure wouldn't prematurely end your cruise for repairs.

Well, not quite. Full max output on my cat means I need 30kw, not 15kw (2 SD15 servoprop motors, 15kw each).

However, yes, I can get along on 15kw, for a cruising speed of about 6 knots.

However, the issue is, if I run just one 15kw generator to motor at 6 knots, nothing is going back into my batteries. So, to motor and charge, I'd have to run two generators, both 15kw.

On the other hand, if I have one 20kw generator, I can motor and charge with only one generator running.

The second 10kw generator is to boost that power to 30kw for max. thrust, in an emergency. Or, if the 20kw breaks, I can still motor on the 10kw (yes, at a reduced speed of maybe 4 knots) but it will get me back to shore. However, most of the time, I would only have to run one generator.

As for a third Honda generator... then I would have to care for three generators, and, that Honda is gas powered. I am a diesel/electric boat, I don't want to carry more gas. The dingy gas is bad enough. On top of that, the Honda can't possibly put out enough power to run my A/C, etc. A 10kw would do all that easily.

**newhaul** · 19-05-2019, 14:41

Quote:

Originally Posted by Jatar

Well, not quite. Full max output on my cat means I need 30kw, not 15kw (2 SD15 servoprop motors, 15kw each).

However, yes, I can get along on 15kw, for a cruising speed of about 6 knots.

However, the issue is, if I run just one 15kw generator to motor at 6 knots, nothing is going back into my batteries. So, to motor and charge, I'd have to run two generators, both 15kw.

On the other hand, if I have one 20kw generator, I can motor and charge with only one generator running.

The second 10kw generator is to boost that power to 30kw for max. thrust, in an emergency. Or, if the 20kw breaks, I can still motor on the 10kw (yes, at a reduced speed of maybe 4 knots) but it will get me back to shore. However, most of the time, I would only have to run one generator.

As for a third Honda generator... then I would have to care for three generators, and, that Honda is gas powered. I am a diesel/electric boat, I don't want to carry more gas. The dingy gas is bad enough. On top of that, the Honda can't possibly put out enough power to run my A/C, etc. A 10kw would do all that easily.

sounds well planned out then looking forward to the build thread and associated pictures .

Jatar · 19-05-2019, 15:47

Quote:

Originally Posted by newhaul

sounds well planned out then looking forward to the build thread and associated pictures .

I'll document the whole thing on video and post it when the time comes. Thank you for offering your suggestions, nothing is yet written in stone, I'm just weighing possibilities up until I buy. Fortunately (or unfortunately, depending on how you look at it) I have about three years to get my ducks in a row before I start my build. I'm waiting to retire from my job, so that sets my timetable. Hopefully, some better batteries come along in that time, but we'll see.

Go Wildcats · 19-05-2019, 16:53

Here's an Oceanvolt Cat walk through with owners comments:
Part 1
https://youtu.be/o6kOvjS1ytE

Part 2
https://youtu.be/nchKhM_TxYk

nebster · 19-05-2019, 19:08

One nice advantage of a 48VDC setup is that you can use it for your house energy bank as well. I didn’t notice if you already factored that into your demand calcs... but your bank could be a good bit bigger, and I know I would prefer it.

I like the 20kw+10kw gen sets, assuming they work together like you describe (no idea). It’s better to run one generator at nearly full bore then to have one loafing along at half power.

BigBeakie · 19-05-2019, 20:54

If you look at your OV speed/resistance curves on your proposal, you may notice that there is not much difference between running the SD15 at 75% ie 10 kW, compared to full power. Diminishing returns. So your 20kW DC genset feeding 10 to each motor is quite reasonable.

As for redundancy on the DC genset, I assume you're in the US, so local PolarPower is the go to option. Suggest to Research their field performance wrt reliability and MTBF if you can. Are they used in any applications by military or telecommunications for remote location, continuous unattended operation?

We were lucky in Australia having a local engineering company making the most reliable DC gensets we could find worldwide, so went with their 16kW Eniquest which puts out 15kW continuous. I believe they have never had a failure of any of their gensets in over 15 years!

If you pick the right DC Genset, and you are absolutely diligent with feeding it clean air and fuel ( 2 micron filtering) and change oil religiously, and you can monitor oil temp, water temp etc., you might reconsider the redundancy aspect on this item vs weight/cost/maintenance penalty.

With regen and enough solar, your daily house loads should be well and truly covered except for more than say 4 days in a row of heavy cloud cover, if at anchor.

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