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post #161 of 243 Old 02-20-2019 Thread Starter
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Re: Electric Conversion log for Kahleesea

Boatsurgeon, I can't answer to all of your statements, so I'll just hit the ones that I can.

1-4) Arc distance for 48V is .6mm. While that's bigger than 12V's .1mm, I can't see any situation where bus bars or terminals could be placed that close together, even if you wanted to. If your concern is dropping a tool into the battery box, I have you covered - I'm putting terminal caps on all of my battery connections so they'll all be insulated.

5) Definitely. When the time comes to actually connect the terminals in my battery box, I will be wearing rubber gloves. While I've been poked occasionally with 120VAC, I don't enjoy the feeling.

6) More likely I would bump my head on the bulkhead of the boat, but point taken.

7) Maybe? Thing is with things like inverters, you get what you pay for. A quick look shows that 48V inverters are marginally (+5%ish) more expensive than 12V inverters of the same power rating.

12) Yes, it does give you a single point of failure. However, for the cost of a 12V battery, charger, and separate wiring, I can buy a dozen 48V to 12V converters, all with an IP67 rating, eliminating the need for a house battery set. Even with a dozen spares in the hold I'm still way ahead in the weight of a single medium sized lead acid batter and all the accoutrements that go with it. This is one of the few times on a boat where it's easier, cheaper and lighter all at once.

14) It's more than justified - it's essential. At 1V = 50 RPM, a 12V motor would get you 600RPM. That might work for a dinghy, but it sure won't push a sailboat at better than a crawl, no matter how many amps you throw at it.

17) Yep, that's me. But as the old 60's Easter special song goes...

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Re: Electric Conversion log for Kahleesea

RE: Somebody has to be first.

Absolutely, and someone may jump the queue to be first to the gallows. ;-)
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Re: Electric Conversion log for Kahleesea

Any number of DC-DC converters are not the same thing as 12 Vdc emergency reserve capacity.

Failure of the 48 Vdc propulsion electrical system renders every DC-DC converter instantly inoperative, and as a result, all 12 Vdc electrical system equipment including safety, navigation, and lighting.

Cripes, the 12 Vdc lighter socket won't even work so you can sit back and have a smoke (along with your hair and the boat) while you reconsider the validity of your choices. ;-)
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post #164 of 243 Old 02-21-2019 Thread Starter
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Re: Electric Conversion log for Kahleesea

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Any number of DC-DC converters are not the same thing as 12 Vdc emergency reserve capacity.

Failure of the 48 Vdc propulsion electrical system renders every DC-DC converter instantly inoperative, and as a result, all 12 Vdc electrical system equipment including safety, navigation, and lighting.

Cripes, the 12 Vdc lighter socket won't even work so you can sit back and have a smoke (along with your hair and the boat) while you reconsider the validity of your choices. ;-)
What, exactly, do you expect will happen to knock out all 4 batteries in the pack at the same time? The batteries are wired in parallel, so any one battery failure just reduces the total capacity available.

Anything I can come up with while sailing that would kill all the batteries at once would also kill me simultaneously or sink the boat, rendering the 12v system irrelevant anyway.
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Re: Electric Conversion log for Kahleesea

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What, exactly, do you expect will happen to knock out all 4 batteries in the pack at the same time?
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post #166 of 243 Old 02-22-2019
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Re: Electric Conversion log for Kahleesea

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What, exactly, do you expect will happen to knock out all 4 batteries in the pack at the same time? The batteries are wired in parallel, so any one battery failure just reduces the total capacity available.

Anything I can come up with while sailing that would kill all the batteries at once would also kill me simultaneously or sink the boat, rendering the 12v system irrelevant anyway.
Could be from a bad connector, bad cable, bad connection, short circuit, blown fuse, corrosion, melted battery post, etc.

All quite common on boats.

Oh, and apparently someone else believes it could be caused by aliens.

(If so, perhaps you should build a big, beautiful wall in your boat.) ;-)

Last edited by boatsurgeon; 02-22-2019 at 02:10 AM.
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Re: Electric Conversion log for Kahleesea

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To each their own.

How do you charge batteries connected in series separately?

For any vessel with an electric propulsion system, I recommend separate isolated systems for propulsion and 12 Vdc for safety equipment, with their own charging sources, double, triple, or quadruple redundancy for the safety.

As mentioned, a bad side effect of that set-up is if you have a propulsion system electrical failure, or a DC-DC converter failure, ya got nuthin' for safety equipment and lighting, till you can tear it apart and re-wire.

Not pleasant if getting beat-up, which is when stuff like this normally happens.

(One shouldn't have a low voltage problem if the electrical system design is properly balanced and maintained.)
I agree. When I converted to EP I kept my house 12 volt bank and kept it separate from my Electric Propulsion bank. I saw no reason to get rid of the working 12 volt house bank and just down convert from 48 volts. I'm a if it ain't broke don't fix it kind of guy. I also don't like to have all the eggs in one basket. I'm glad I did it this way. Last summer I had issue with a breaker in the EP system. I had to disconnect the 48 volt bank for a few days while I figured it out. Never had to worry about the house bank since it was separate and kept working as usual including refrigeration.
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post #168 of 243 Old 02-22-2019 Thread Starter
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Re: Electric Conversion log for Kahleesea

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Could be from a bad connector, bad cable, bad connection, short circuit, blown fuse, corrosion, melted battery post, etc.

All quite common on boats.

Oh, and apparently someone else believes it could be caused by aliens.

(If so, perhaps you should build a big, beautiful wall in your boat.) ;-)
Common on brand new installations? I think not. I would be surprised if any of these issues regularly occurred on boats that were less than 5 years old and unmodified from factory spec. I have no doubt they are much more common on older boats. But we're talking about a new install, so we can safely dispense with any issues that crop up due to age or wear. I'll grant that poor design or installation could still be an issue, but hopefully my research matches my wrench-turning skills and I do everything right, or at least right enough. If anything, I tend to over-engineer things (My PC, for example, has a 1100W power supply, but draws under 500W maximum in it's current configuration).

One other thing - corrosion isn't a thing for lithium batteries, at least not the same way it is for lead-acid. The chemicals that cause corrosion on lead-acid batteries don't exist in lithium batteries, and the terminals are stainless. The copper in the wires I'm using to connect the batteries to the terminals will eventually corrode a little, but I doubt that will affect anything, even over the long term.

So far, the battery box design has a series of 2/0 105C cables connecting the terminals of the batteries to their respective common terminals that penetrate the box. Outside the box, the hot terminal will connect to a 200A circuit breaker. This will double as a hard on/off switch. The motor mains (also 2/0 105C) will run from the box to the controller, and the 12v converter will connect and live outside of the box. The battery box is ABYC compliant. All the batteries are getting terminal caps inside the box. The BMS runs on .15A max (.06A typ, .001A idle), so it generates negligible heat and will be living inside the battery box.

Anyway, the mechanical parts are showing up soon, so once they are breadboarded I'll run the system at full power and run some tests. I'm anticipating no more than a 10F temperature spike in the batteries, even under full load. I will, of course, post the results as soon as I have them. Maybe even a YouTube video if I can convince my daughter to film it for me.
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post #169 of 243 Old 02-22-2019
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Re: Electric Conversion log for Kahleesea

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Common on brand new installations? I think not. I would be surprised if any of these issues regularly occurred on boats that were less than 5 years old and unmodified from factory spec. I have no doubt they are much more common on older boats. But we're talking about a new install, so we can safely dispense with any issues that crop up due to age or wear. I'll grant that poor design or installation could still be an issue, but hopefully my research matches my wrench-turning skills and I do everything right, or at least right enough. If anything, I tend to over-engineer things (My PC, for example, has a 1100W power supply, but draws under 500W maximum in it's current configuration).

One other thing - corrosion isn't a thing for lithium batteries, at least not the same way it is for lead-acid. The chemicals that cause corrosion on lead-acid batteries don't exist in lithium batteries, and the terminals are stainless. The copper in the wires I'm using to connect the batteries to the terminals will eventually corrode a little, but I doubt that will affect anything, even over the long term.

So far, the battery box design has a series of 2/0 105C cables connecting the terminals of the batteries to their respective common terminals that penetrate the box. Outside the box, the hot terminal will connect to a 200A circuit breaker. This will double as a hard on/off switch. The motor mains (also 2/0 105C) will run from the box to the controller, and the 12v converter will connect and live outside of the box. The battery box is ABYC compliant. All the batteries are getting terminal caps inside the box. The BMS runs on .15A max (.06A typ, .001A idle), so it generates negligible heat and will be living inside the battery box.

Anyway, the mechanical parts are showing up soon, so once they are breadboarded I'll run the system at full power and run some tests. I'm anticipating no more than a 10F temperature spike in the batteries, even under full load. I will, of course, post the results as soon as I have them. Maybe even a YouTube video if I can convince my daughter to film it for me.
FWIW, new installations are far, far, far, more likely to have faults. (At a certain age, fatigue faults increase.)

It is not uncommon for a vessel to require significant repairs after the maiden voyage to address all of the "new installation" faults.

And yes corrosion is a problem on boats.

Stay safe.
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Re: Electric Conversion log for Kahleesea

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I think there are some advantages to this arrangement -- Electric prime mover for the reliable quick anchor set/docking/get out of the way/short hop, and diesel genset for induction cooktop, microwave and air conditioning at anchor, and longer 30-40 hours of motoring @ 5kts. It's the direction I'm going.


Sean
I'm glad someone else had this thought too.

nigel Calder is working on his boat and is doing something similar.

He wants to get to a single fuel boat, diesel with electric.

It is not cheap however but he is working out all the math to at least make the running no more expensive.

Apparently, you can get insanely efficient genset numbers along with very long lifetimes.

He is working on tech so that whenever the genset is running it is running with optimal efficiency. Any extra energy is automatically stored.

An ICE propulsion motor is often not running efficiently but converting from gen-set to electric propulsion has conversion costs but he thinks he can do the tech so the hybrid design is ultimately more efficient.

He actually passed that idea off to someone else and is working on a controller and power generator alternator replacement that will add load to the engine whenever it is not running at WOT until the engine is at optimal efficiency and store the energy in lithium batteries and eliminate the need for a genset.

The lesson from the Icarus story is not about human failing.
It is a lesson about the limitations of wax as an adhesive.
If you have an engineering problem solve it.

Last edited by davidpm; 02-22-2019 at 11:42 PM.
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