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post #141 of 282 Old 01-17-2019 Thread Starter
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Re: Electric Conversion log for Kahleesea

I need some opinions, guys.

Issue #1:

The Particle photon runs on 3.3-6.5 vdc. 5.5 is recommended.

The only solution I can come up with to keep it powered 100% of the time is to run it off of the battery itself through a DC-DC converter. Is there a better way?

Issue #2:

I'd like to run each battery on it's own BMS, but I'm having a hard time finding relays that work off of the particle's 5v 100mA output. There are tons of them for 120V, but when I start looking for 48VDC 200A relays, I only find relays that the particle has no hope of pushing closed. If I use a 120vac relay, that means either one battery shuts the whole pack down, or I need a charger for each battery. It would be a lot less expensive if I could just find a relay for each battery. While I'm sure using one BMS for the whole system would work, It's more optimal to do a bms for each battery.

As always, I'm open to ideas.
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post #142 of 282 Old 01-17-2019
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Re: Electric Conversion log for Kahleesea

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Originally Posted by Captain Canuck View Post
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.
Here are 5 reasons I can think of off the top of my head (not in any particular order):

1. Most individuals purchasing a boat want either a cheap project boat (low cost, least work possible) or a sail-away (higher cost, but no work). Best guess is this project boat will be high cost and tons of work.

2. Very few potential buyers will have the technical know how and skills to carry it through properly and safely.

3. All parts depreciate significantly the instant one takes them out of the box, again with ownership transfer (lost warranties) and then the depreciation rate tails off with time, based on the ALE (Average Life Expectancy).

4. While every individual part may actually last longer or shorter than ALE, depreciation is typically based on the average. Any life beyond that is borrowed time, and expensive repair or replacement may well be required soon.

Typical Estimates:
Hull - 30 years
Diesel Motor - 25 years
Electrical Wiring - 15 years
Electric Motor - 10 years (in salt water environment)
Electronics - 10 years
Sails - 20 years (cruiser), 10 years (avid sailor) 5 years (active PHRF club racer), 2 years (interclub trophy winner).

5. High risk - There is no guarantee the design will ever work satisfactorily.

Hope this helps.
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Re: Electric Conversion log for Kahleesea

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Originally Posted by mstern View Post
Someone to learn from/cautionary tale:

https://sfbay.craigslist.org/sfc/boa...781895607.html

Quote:
90% complete, staged and tested off-site prior to installing, you can finish, electrical/mechanical/operational (our major effort) - a couple weeks to sea trials
What this actually means is that it's 15% and at least a year from sea trials.

Catalina 22
on a starboard tack
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Re: Electric Conversion log for Kahleesea

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Originally Posted by boatsurgeon View Post
Here are 5 reasons I can think of off the top of my head (not in any particular order):

1. Most individuals purchasing a boat want either a cheap project boat (low cost, least work possible) or a sail-away (higher cost, but no work). Best guess is this project boat will be high cost and tons of work.

2. Very few potential buyers will have the technical know how and skills to carry it through properly and safely.

3. All parts depreciate significantly the instant one takes them out of the box, again with ownership transfer (lost warranties) and then the depreciation rate tails off with time, based on the ALE (Average Life Expectancy).

4. While every individual part may actually last longer or shorter than ALE, depreciation is typically based on the average. Any life beyond that is borrowed time, and expensive repair or replacement may well be required soon.

Typical Estimates:
Hull - 30 years
Diesel Motor - 25 years
Electrical Wiring - 15 years
Electric Motor - 10 years (in salt water environment)
Electronics - 10 years
Sails - 20 years (cruiser), 10 years (avid sailor) 5 years (active PHRF club racer), 2 years (interclub trophy winner).

5. High risk - There is no guarantee the design will ever work satisfactorily.

Hope this helps.
1. I can see that.

2. This is certainly true. I could count the number of electric boat enthusiasts I've met in the Annapolis area on one hand, and most of those were selling things.

3. Sure. Same with pretty much any personally-owned transportation devices, from a scooter to a Rolls Royce. With certain cars, the curve eventually starts moving up again, but that's pretty rare. I've never seen a boat that appreciates. It's one of the things that makes them a good tax deduction.

4. Those are some seriously conservative lifetime expectations. Sounds like they were cooked up by West Marine to sell parts. Seriously though, unless you abuse your equipment, they should all last considerably longer than that. Except the sails - they are definitely on a flat use to wear curve. 40 year old motors and hulls aren't uncommon, provided they are maintained properly.

5. 'satisfactorily' is entirely subjective. I appreciate the guy's initiative and willingness to try, though. Maybe, like me, he's aiming for a design where he can replace the batteries down the road when the technology improves. A 50kWh pack won't get him too far, but a 500kWh pack certainly would. Who knows where we'll be in 5, 10, 20 years?
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Re: Electric Conversion log for Kahleesea

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What this actually means is that it's 15% and at least a year from sea trials.
Heh. Maybe. People do tend to exaggerate their achievements at times. Though honestly, with the batteries and motors in place, that's a good chunk of the physical work complete.

I wish I lived closer so I could run down and take a look at it. It could be a sloppy mess, or it could be an engineering masterpiece. Either way, it would be educational.
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Re: Electric Conversion log for Kahleesea

Boat Surgeon

Quote:
4. While every individual part may actually last longer or shorter than ALE, depreciation is typically based on the average. Any life beyond that is borrowed time, and expensive repair or replacement may well be required soon.

Typical Estimates:
Hull - 30 years
Diesel Motor - 25 years
Electrical Wiring - 15 years
Electric Motor - 10 years (in salt water environment)
Electronics - 10 years
Sails - 20 years (cruiser), 10 years (avid sailor) 5 years (active PHRF club racer), 2 years (interclub trophy winner).
Captain Canuck:

Quote:
4. Those are some seriously conservative lifetime expectations. Sounds like they were cooked up by West Marine to sell parts. Seriously though, unless you abuse your equipment, they should all last considerably longer than that. Except the sails - they are definitely on a flat use to wear curve. 40 year old motors and hulls aren't uncommon, provided they are maintained properly.
Au contraire mon ami.

Remember we are talking ALE.

Not maximum life expectancy, not 96th percentile on the bell curve...

...average.

Northern freshwater may do better, saltwater near the equator worse.

You are absolutely correct that some diesel motors may last 40 years or even longer, but others are killed by 20, some as young as 4 (not coincidentally about the ALE of a raw water pump impeller).

Anyway, the actual ALE figures aren't so important, the point is, parts depreciate in value within this period, fast initially and then tapering off.

I hope you considered this realistically into your plans.
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Re: Electric Conversion log for Kahleesea

Quote:
Originally Posted by Captain Canuck View Post
I need some opinions, guys.

Issue #1:

The Particle photon runs on 3.3-6.5 vdc. 5.5 is recommended.

The only solution I can come up with to keep it powered 100% of the time is to run it off of the battery itself through a DC-DC converter. Is there a better way?

Issue #2:

I'd like to run each battery on it's own BMS, but I'm having a hard time finding relays that work off of the particle's 5v 100mA output. There are tons of them for 120V, but when I start looking for 48VDC 200A relays, I only find relays that the particle has no hope of pushing closed. If I use a 120vac relay, that means either one battery shuts the whole pack down, or I need a charger for each battery. It would be a lot less expensive if I could just find a relay for each battery. While I'm sure using one BMS for the whole system would work, It's more optimal to do a bms for each battery.

As always, I'm open to ideas.
any relay running at 5v/100ma is a tiny little relay that doesn't have the spark gap to stop the other 46v + inductance of the whole circuit (Read: You will get a voltage surge when your relay trips, and that will weld the contacts the first time it opens under load)

The only thing your individual cell monitor needs to do is bleed the cell for balancing and alert for under voltage/over voltage. The alert lines should be opto isolated for safety to the main BMS unit, and engineer it to it keep the alert lines at the same relative voltage to each other (since they'll have a lot less insulation on them than the primary conductors). There's no point in putting a relay on each cell since the cells are all in series...any one relay trips you shut the whole bank anyways. You cannot realistically take one cell out of the circuit, since each set of relays to do that would have to be rated at max system current and voltage. That's expensive.

Better and far less expensive to use one big assed fat contactor to shut the bank down and just trigger it on HV or LV events.

The individual cell monitor is probably better off a very simple low power 1.2v digi device with a dedicated AD, or a pure analog device, though pure analog devices are hard to calibrate/maintain calibration over temperature ranges. A commercial solution that has had decades of sound engineering behind it coupled with practical application experience is really the only safe way to go esp. considering your desire to use less forgiving LiIon vs. LiFePO4.

If I remember correctly there are some BMS projects on https://endless-sphere.com/forums/ if you want to look at people's design thoughts on the subject. After you become familiar with the sheer magnitude of what you are trying to do I think you may reconsider either the chemistry or the bms(Though again, i recommend reconsidering both.) I looked into BMS design figuring it can't be that hard. And I'm really familiar with eletronic design, have had my own circuit boards printed, have etched them myself, built transmitters, antenna tuners, antenna tuner control circuits, programmed Microchip PIC and Atmel microcontrollers, I code in a plethora of languages c c++ python etc... and while I enjoyed learning about BMS design, I decided it would be hubris to pursue it.

YMMV but I don't recommend it.
Sean
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Re: Electric Conversion log for Kahleesea

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any relay running at 5v/100ma is a tiny little relay that doesn't have the spark gap to stop the other 46v + inductance of the whole circuit (Read: You will get a voltage surge when your relay trips, and that will weld the contacts the first time it opens under load)

The only thing your individual cell monitor needs to do is bleed the cell for balancing and alert for under voltage/over voltage. The alert lines should be opto isolated for safety to the main BMS unit, and engineer it to it keep the alert lines at the same relative voltage to each other (since they'll have a lot less insulation on them than the primary conductors). There's no point in putting a relay on each cell since the cells are all in series...any one relay trips you shut the whole bank anyways. You cannot realistically take one cell out of the circuit, since each set of relays to do that would have to be rated at max system current and voltage. That's expensive.

Better and far less expensive to use one big assed fat contactor to shut the bank down and just trigger it on HV or LV events.

The individual cell monitor is probably better off a very simple low power 1.2v digi device with a dedicated AD, or a pure analog device, though pure analog devices are hard to calibrate/maintain calibration over temperature ranges. A commercial solution that has had decades of sound engineering behind it coupled with practical application experience is really the only safe way to go esp. considering your desire to use less forgiving LiIon vs. LiFePO4.

If I remember correctly there are some BMS projects on https://endless-sphere.com/forums/ if you want to look at people's design thoughts on the subject. After you become familiar with the sheer magnitude of what you are trying to do I think you may reconsider either the chemistry or the bms(Though again, i recommend reconsidering both.) I looked into BMS design figuring it can't be that hard. And I'm really familiar with eletronic design, have had my own circuit boards printed, have etched them myself, built transmitters, antenna tuners, antenna tuner control circuits, programmed Microchip PIC and Atmel microcontrollers, I code in a plethora of languages c c++ python etc... and while I enjoyed learning about BMS design, I decided it would be hubris to pursue it.

YMMV but I don't recommend it.
Sean

Even if I put one big ass relay in place, I still need to find said big ass relay, and a way to actuate it.

The batteries will be in parallel, not in series. This is why I'm trying to see if it's possible to cut one out if it goes bad while under power, so I only lose some run time instead of stopping the boat dead. I agree that it could get pricey, but so does one charger per battery.

I'm not afraid of difficult tasks. That's how you learn. That being said, looks like I'm being Quixotic in building my own BMS. I didn't think there were any off the shelf commercial models available, but apparently, there are. I'll dig into that and see if I can find something that will work. At least the converter and inverter are relatively straightforward and there's plenty of off the shelf parts available.
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Re: Electric Conversion log for Kahleesea

Update, 1/18/19

Khaleesea is out of the water. Looks like the barnacles took a toll on her paint. No blistering though. I'm going to leave her on the hard for the next 3 months to let her dry out.

Picked up the new prop today. After measuring the available space, I'm going with a 15x17x3 prop to replace the old 15x12x2, which is in less than stellar shape. I've brought it home for a bit of polishing and a shot of zinc galvanizing compound. I bought it used, because I'm a cheap bastard. Don, the prop guy, has been incredibly patient with me and my extremely limited knowledge of props. He's a real craftsman, and was kind enough to lend me his prop puller so I could yank the old prop today.

I would have loved to try for a bigger prop, but unfortunately the 15" stock prop was already the absolute max diameter available for the space. It would take a serious amount of hull construction to go with a bigger prop, which isn't worth it.

This sets my gear ratio at 2:1, so no whacky custom parts will be necessary.

Unfortunately, the BMS is turning into a thornier problem than I had anticipated. Looks like I might have to go with an off-the-shelf BMS and see if I can adapt it to my needs. I didn't even know they existed, but fortunately, they do. Looks like I'll need a few more boat bux to finish this project. Good thing I didn't set a hard budget for it.
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khaleesea new prop.JPG   Khaleesea old prop.JPG   khaleesea hull.JPG  
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Re: Electric Conversion log for Kahleesea

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The batteries will be in parallel, not in series.
Uh, so your BMS isn't going to monitor cells, it's going to monitor packs only? 48v nominal packs in parallel?

Sorry, I'm confused. To be safe, a BMS has to monitor at the cell level. If a LiIon cell for whatever reason becomes out of balance with the rest of the pack, bad things happen. Like they get over charged and catch on fire. Or if under capacity, they can get driven into reverse voltage, which damages them and further lowers capacity, and on the next charge cycle get over charged and catch on fire...all while your pack level 4.2v*cell count cutoff voltages never trigger....

Sorry if I missed this detail before..


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