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post #131 of 283 Old 01-15-2019
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Re: Electric Conversion log for Kahleesea

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Originally Posted by Captain Canuck View Post
My point is, even the most brilliant expert can be wrong. Sometimes experience works against us, and we encounter something so far outside of the norm that we can't believe it's true. This is why solid, objective diagnostic skills are so very important in any job where you fix things.
This is an interesting point.

While it is possible for experience to work against, it is a very, very, rare occurrence.

I used to be a Product Development Team Leader for various manufacturers, when there was actual research and development vs outsourcing going on in North America.

I absolutely agree with you that, "We are going to do it this way, because it is the way it has always been done." is very bad reasoning.

But none of us can foresee the future with any clarity, yet hindsight is always 20/20.

Nothing stands to screw up a project more than disregarding core competency and introducing unproven materials and/or designs, hence the need to separate "research" from "development".

"Development is where the low hanging fruit is, fast, predictable, low risk and low risk.

"Research is where the highest potential gain is, but with uncertain timing at the highest risk.

"Research and development" in the same project will getcha almost every time.

This is why for someone with no prior experience developing an electric propulsion system, I recommend considering a solution from a system integrator with a proven design.

You still have an incredible learning opportunity, and get the reward of a system that you selected and installed, but at a lot lower risk, and you get the benefit of their experience doing the same thing, again and again and again, at no or low cost, with all kinks and failed design attempts already worked out of the equation.

Even though the VAR purchase price may seem higher than individual components made who knows where, by who knows who, with I don't know what level of integrity (think Abbot & Costello's "Who's on first?" gag), the installation will likely be much faster, less risky, and lower total cost.

Your boat, your project, your choice.

Last edited by boatsurgeon; 01-15-2019 at 10:45 AM.
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post #132 of 283 Old 01-15-2019
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Re: Electric Conversion log for Kahleesea

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RF only travels on the surface of a conductor. 0000 cable has a radius of .23", so a circumference of 1.45". That's not a lot of surface area and represents a high impedance to RF relative to the say, 4" surface area of 2" wide strap, or far better the 12" surface area of 6" wide copper strap. When grounding for lightning...use strap. Far superior RF conduction for the amount of copper. https://www.gacopper.com/ is a great source used by amateurs and professionals. Lot of good information on grounding linked from that site too.
You know, I'm going to semi-correct myself here. Strap is perfect on installations that don't suffer vibration or mechanical movement. When transitioning between things that suffer mechanical movement, you may want to use tinned braid, which is better than solid wire but several times the impedance of equivalent width solid strap at RF. Key here is that braid won't crack due to metal fatigue/work hardening and solid strap will.

Either way, make it a point to include inspecting your ground strap(system) at a regular basis if you want to maintain the protection it provides. And lightning doesn't like bulb keels as much as it likes sea surface, even though bulb keels do work to ground the energy. Lightning wants to be at the surface of the sea, not flowing along the border between the sea and the side of your hull from the keel to the surface. That border induces capacitance to the 'plate' that is formed and capacitance (along with inductance) creates impedance to AC/RF. Sharp bends are high impedance, too. you want long curves in your lightning ground path. You can make lightning exit through the bulb keel. You just have to make that path to the surface a lower impedance at RF than taking a shortcut through the side of the hull would be.

Anyways, more interesting radio stuff.

/end self-correction
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post #133 of 283 Old 01-15-2019
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Re: Electric Conversion log for Kahleesea

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Captain Canuck, I just want to reiterate that I am on your side -- I am also doing an electric conversion and I am just urging a holistic approach to engineering the boat as a system, and understanding the effects of uncontrollable, unexpected events on that system. And, I keep posting, um, lets say "strong suggestion" posts because I'm not just trying to help you, I'm trying to help everyone reading this thread too. Ultimately, what you do with your vessel is your business, I just want you to be successful. With that said...



My FCC issued call sign is WK7R, I am an extra class ham radio operator. Out in Arizona (as in many other places...) we do things like put repeaters/antennas next to commercial equipment that is mounted to 100'+ towers on the top of 7000' mountain peaks that get struck by lightning quite often -- as in multiple times every time a storm blows by. A large part of the body of knowledge in our hobby at this level has to do with effectively managing the 30,000+ amps of RF energy (Lightning current amplitude rises and falls so fast, the energy is effectively at radio frequencies and behaves as such, so we refer to lightning as RF energy) and protecting sensitive equipment (and dwellings, and people) from damage in this environment.

I guess I'm saying in no uncertain terms that I am better equipped to make a guess about what happens when lightning strikes your boat than you are, no offense intended. Please do look into the subject. It's actually one of the fascinating ones, that's a lot of fun to learn about. Things like how electricity at RF only conducts on the surface of conductors (That's why Faraday cages work). The sea is a conductor too, and when your boat is struck by lightning, often it travels down the outside of your mast, until the high impedance, low surface area ground cable turns a little too sharply toward a thru hull and the lightning finds a shorter, lower impedance path to the surface of the sea by blowing a hole through the side of your hull causing a pinprick leak at the water line, that may wind up sinking your boat.

The fact that lightning at 30 million volts that just arced through say 3000 feet of free air are going to LAUGH at the 1/4" arc gap in your fuse as it turns into a conductive cloud of plasma.

The fact that lightning is at such immense current that it creates an incredible magnetic field as it flows through conductors (including the air..) and actually induces (as in magnetic induction) current in nearby parallel conductors (including signposts, masts, shrouds and humans who happen to be standing near by,) turning them into the secondary winding in a transformer such that even though the conductor may not be directly involved in the strike path, damaging currents flow (including enough to kill people, erase RAM, corrupt flash memory, fry transistors and FETs that fail shorted...)

Look into boat lightning strikes/near strikes. It's really scary the crazy things that can happen. And while even if we know how to manage lightning energy on towers and radio shacks on the tops of mountains, the same techniques are almost impossible to effectively employ on a fiberglass hulled boat like yours and mine. The insulation of the glass really works against us in the attempt to make the whole boat, as an electrical entity, rise and fall together with the voltage potential of the surface of the sea. It's just not realistic to effectively do that. Steel and aluminum boats are in a much better position in that regard. I guess the point is You Should Expect Every Electrical Device On Your Boat To Fail In The Worst Possible Way It Can.

While we will still build cool boats out of glass, or retrofit them with all manner of propulsion and sail them in spite of the forces of nature, we might as well make them somewhat failsafe so that even if everything shorts, every electronic device subject to the invisible electrical, magnetic, and electromagnetic forces of nature is destroyed... the consequences will still be manageable if, heaven forbid, we are on that boat when the worst happens.

And a for the record.. https://www.boatus.com/magazine/2017...ng-strikes.asp the national average is 1 in 1000 sailboats are struck per year. And 3.3 per 1000 in Florida..

That's the stuff that keeps me awake at night... until it's actually storming. Then there's really nothing left to do after making fast to your mooring than to raise your drink, toast to life, and pray to God that you've done enough to prepare.

Personally, I don't want to be weighed in the balance and found wanting.


Sean

P.S. Dude I am totally sorry for all the big long preachy posts, I don't mean to be so damn serious. There's just a lot of really interesting things out there that I've spent a long time trying to learn..figure I'd try to save you the trouble of a lot of the research.
Sean

Thanks for the primer on lightning and it's dangers regarding boats. I was reminded that it was another reason I was avoiding going with Lithium ten years ago when I did my EP conversion. My boat was never struck by lightning but, pretty sure it received the effects of a side strike. I had several electrical items suddenly stop working at the same time. From a pretty robust brute force battery charger to one of the solenoids to my electric windlass among other items. I then wondered what a strike or side strike would do to the electronics of a BMS system that was monitoring the Lithium battery bank. IMO there was to much complexity compared to going with AGM batteries. It was also a reason I like my off the shelf LEMCO motor. In a pinch I could run the motor directly off the batteries should the controller get zapped too.

Mike
Currently: Heading to warm waters over the winter on a variety of boats.

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post #134 of 283 Old 01-15-2019
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Re: Electric Conversion log for Kahleesea

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Originally Posted by texlan View Post
You know, I'm going to semi-correct myself here. Strap is perfect on installations that don't suffer vibration or mechanical movement. When transitioning between things that suffer mechanical movement, you may want to use tinned braid, which is better than solid wire but several times the impedance of equivalent width solid strap at RF. Key here is that braid won't crack due to metal fatigue/work hardening and solid strap will.
(May wish to check ABYC standards on this.)
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Re: Electric Conversion log for Kahleesea

Sean-

So when lightning strikes, even if it doesn't directly contact the electronics, it's the RF surge that knocks everything out, right? Could that be blocked by a grounded sheet of conductive metal between the mast and the electronics on the boat, or would they have to be fully encased a la Faraday cage? I'm trying to grasp the physics of what's happening. I find once you grasp that, you're more than halfway to a solution, or realizing there isn't one.

boatsurgeon-

You're right, it is rare. Usually such mistakes are born of complacency. I've certainly made that mistake once or twice. That's why it's so vitally important to look at the data closely and with an open mind. Just because no one's seen it before doesn't mean it didn't happen. Sometimes, weird **** goes down with no real explanation, and no amount of digging into the data offers a reason for it.

Thanks again for all the great info guys.
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post #136 of 283 Old 01-15-2019
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Re: Electric Conversion log for Kahleesea

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(May wish to check ABYC standards on this.)
Agreed.

This is one place, though, where I think you can (if you know what you're doing) exceed the standard by both A) adhering to it (ie the 4 awg stranded copper ground from the mast to the keel bolt/grounding plate) and b) expanding on it (coupled with a copper strap downconductor as proven in commercial radio installations) so long as you adhere to the single point ground concept and make sure all of your conductors will rise and fall together. A low impedance wide/thick copper copper bus (strap) from stem to stern to serve as the bonding bus in the system will additionally serve to allow the whole boat to rise and fall together with lower voltage gradients.

The 'standard' stranded conductor will serve as a fine backup should the lower impedance path from the mast be broken for any reason.

The fact is, in my sometimes not so humble opinion, the standard is a bare minimum in the case of lightning and while it does often result in saving the boat from sinking per se, the voltage gradients in the in the ABYC specified but woefully inadequate ground system itself still wreak havoc, generating circular current flows through the grounds of electrical equipment interconnected by NMEA2000 networks and such. This leaves you with a floating but unreliable boat.

Just an opinion though.
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Re: Electric Conversion log for Kahleesea

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Sean-

So when lightning strikes, even if it doesn't directly contact the electronics, it's the RF surge that knocks everything out, right? Could that be blocked by a grounded sheet of conductive metal between the mast and the electronics on the boat, or would they have to be fully encased a la Faraday cage? I'm trying to grasp the physics of what's happening. I find once you grasp that, you're more than halfway to a solution, or realizing there isn't one.
It's complicated. A lot of things are happening at once. Current is induced to flow in conductors adjacent to the strike path due to magnetic inductance. This current (along with the lightning strike itself) rises and falls in amplitude at frequencies that are considered radio frequencies. We call it RF as opposed to low frequency AC current or DC current not because it's radiating electromagnetic waves (it's doing that too, though) but because it behaves in a peculiar way compared to AC or DC when it flows through conductors (the surface, not the core) and semiconductors (Diodes in rectifiers and capacitors are mostly transparent to RF) So this massive energy is traveling backwards and forwards relative to the intended direction through the semiconductors, often reaching voltage swings that pop sensitive semiconductor material.

Additionally there is a concept of a voltage gradient. As current travels through a relatively high impedance conductor toward a low impedance ground (OR over a high impedance ground plane..) The voltage at physical point in the conductor and say, another point 2 feet away, is wildly different due to voltage drop. Differences of 300-400 volts are easily measurable over a foot. It all depends on how high the impedance of the conductor is. More impedance, higher voltage gradient. If you are standing on that conductor with your feet apart, your body instantly becomes a lower impedance path, and current will take a shortcut through your legs from the higher voltage gradient to the lower voltage gradient. This is why you are told to keep your feet together in a lightning storm or around a downed power line. Hopping is better than walking.

Imagine that you have a radio and a chart plotter both bonded several feet apart on the same ground wire that eventually makes it to your boat's lightning ground. Those devices are also connected together via NMEA2000 network for AIS data and DSC. The ground wire, being round and of small surface area, presents a relatively high impedance to RF energy. During a direct strike event, the voltage gradient on the ground wire will cause current to flow up the equipement grounds to the equipement, and through your NMEA cable between your electronic components, very likely smoking something in the process as the gradient can be quite large depending on how far away the equipment grounds are from each other over the wire.

The only solution to that is a single point ground system where every ground comes together at one point, preferably at your lightning ground. It still won't save your equipment from inducted currents (nothing will) but it does resolve the voltage gradient (provided that no one piece of equipment was involved in the strike) because all of the equipment will rise in voltage potential and fall in potential at the same time, resulting in no current flowing between the equipment. Unfortunately, your radio antenna if its at the top of the mast, was probably involved in the strike. But you can ground your coax through a gas arc tube protector like https://www.dxengineering.com/parts/...UaAm18EALw_wcB that is bonded to your single point ground, and that'll limit the rise on the center pin to 40 or 50 volts or so, which is fine for most radio receivers.

Anyways blah blah blah i have to work some today so..

The best solution is a metal hulled & decked boat. Which is a faraday cage. Which so long as you bond everything that comes into the hull correctly, will save you. Glass...well, it's finding the best compromise.

Quote:
Thanks again for all the great info guys.
Thanks for being receptive!

Sean

Last edited by texlan; 01-15-2019 at 01:25 PM.
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Re: Electric Conversion log for Kahleesea

Update 1/16/19

Khaleesea is coming out of the water. I had to go remove the jib before they would do it. Learned a new skill - how to loose a knot completely encased in ice. Not one I ever hoped to have to learn...

The brain of the BMS came in. I'm going with a particle photon - which is a remote-programmable wifi-capable electronic controller. It has a ton of features that I like.

- $19, so I can build one per battery without nuking the budget.
- Simple programming language with tons of pre-built scripts you can use for free
- Plenty of pins to control
- WiFi capable
- Remotely programmable
- App for phone or home server monitoring (I have both).
- <1W power consumption when running at maximum, <0.1W in sleep mode
- Did I mention it's $19?

I bought a kit for $89 that came with the unit and quite a lot of extra hardware. It's easily enough for a single battery's BMS with a lot left over. It might not be enough for all 4 BMS', but we'll see.

Let the tinkering begin!
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Re: Electric Conversion log for Kahleesea

Someone to learn from/cautionary tale:

https://sfbay.craigslist.org/sfc/boa...781895607.html
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Re: Electric Conversion log for Kahleesea

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Someone to learn from/cautionary tale:

https://sfbay.craigslist.org/sfc/boa...781895607.html
I don't think the state of technology today would make the average electric power boat even remotely economically viable. As a secondary propulsion, sure, but as primary? Not so much. That being said, you might be able to convert a slow-moving trawler to electric with acceptable results, like an Albin 27.

The *minimum* motive power on a stock Duffy 35 is 200hp. Even assuming no losses, that means the 50kWh pack would last 20 minutes at full 200hp output. So you might be able to cruise at 8-10 knots for a couple of hours. Plus, without a sail, you've got no regen.

They spent an eye-popping 100k, so they're obviously much wealthier than I am.

I don't know why he's selling it so cheap. The motive components alone are worth far more than 10k. I doubt you could buy all that for less than 25K.
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