Electric Conversion log for Kahleesea - Page 16 - SailNet Community
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post #151 of 282 Old 01-18-2019
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Re: Electric Conversion log for Kahleesea

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Originally Posted by Captain Canuck View Post
Update, 1/18/19
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.
Good on you bringing a prop back from the dead.

Sean
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post #152 of 282 Old 01-18-2019 Thread Starter
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Re: Electric Conversion log for Kahleesea

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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..


Sean
No worries. Just to be clear, the batteries have an 18 pin connector to monitor the cells and the temp sensor for the pack. The pack will be charged at the 48v level, but the individual cells will be monitored. I'll just have to find a sufficiently robust BMS that can monitor all those cells and temperature sensors.
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post #153 of 282 Old 01-28-2019 Thread Starter
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Re: Electric Conversion log for Kahleesea

Update 1/28/2019

Cleaned and treated the new prop as per the prop guy's instructions. Then I tried to mount it.

Turns out it's a 1 1/8", not a 1", as is stamped on the prop. It was sitting far too high on the shaft. I can't believe that I was stymied by the propeller equivalent of a typo.

The guy who sold it to me has offered me a brass bushing at cost. It will be in on Thursday.

In other news, I've found what I think will be a good BMS that I can adapt to my needs without too much trouble. Once that comes in I'll work on getting that part functional.
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post #154 of 282 Old 02-06-2019 Thread Starter
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Re: Electric Conversion log for Kahleesea

Update 2/6/2019

...so apparently I suck at installing props, so I'm going to hire someone to do it. Even with the bushing I was unable to get the prop to seat properly. I'm just not willing to invest $100+ for a tool I'm likely to only use once. I have a garage full of that kind of tool already.

The brain of the BMS is on order. I'll purchase the expansion modules if I can get it to work with the batteries I have. As much as I enjoy building things from scratch, this is just too important to leave to a homebrew solution.

I found a nice 48v to 12v 30A DC-DC converter that's waterproof. Totaling up all of my 12v stuff netted me about 18 amps total, so this gives me a comfortable margin. I was surprised to find my cold machine only draws 6 amps when running. I expected that to be higher. Once everything is in place, I'll turn on all the DC circuits and check the draw just to be certain. Even at full draw from the converter, the batteries will last about 24 hours when fully charged.

I'm curious as to how much regen I'm going to get when under sail. There doesn't seem to be a lot of info out there about it. I will provide a full accounting once Kahleesea is back in the water sometime in April.
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post #155 of 282 Old 02-12-2019 Thread Starter
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Re: Electric Conversion log for Kahleesea

Update 2/12/2019

BMS came in. I'm having issues with it. It's supposed to auto-detect the battery when you connect it to the unit, but even after triple checking the wiring to the harness, it's not detecting the battery.

Tech support says everything looks right, and the wiring harness tester says everything is wired correctly. The next step is to crack the BMS box and look for damaged electronics. Hopefully I didn't do anything to let the magic smoke out.

I've found a great battery box that is just the right size for my batteries. It's a marine grade box for a pair of 8D batteries, but has enough room for all four of my lithium batteries, the BMS and the 12V converter. This will simplify the wiring outside of the box tremendously. I also found a 200A marine grade 48V breaker that will double as a hard on/off switch for the motor. I'm thinking a second smaller breaker for the converter would also be a good idea.

Now I arrive at another important decision. Do I put heating in the battery box, so I don't have to pull the batteries out of the boat in winter (they're supposed to be kept over ~50F 24/7) or do I design the box to make the batteries easy to remove so I can store them indoors? I'll have to think on this one.
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post #156 of 282 Old 02-18-2019 Thread Starter
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Re: Electric Conversion log for Kahleesea

Update 2/18/2019

Figured out the problem with the BMS - one of the two boards has bad resistors. Replacement board is on the way.

The prop will be pulled and reseated in the next two weeks.

The battery box and accessories came in on Friday. After a little experimentation, I've figured out how to fit the BMS, DC/DC inverter, and the four batteries into the box and how to run the wiring efficiently. The exterior will have two through connectors for 48V power, two leads from the 12vdc converter, and a connector for the charger. The batteries are wired inside the box in parallel, with identical-length cables so they all get charged identically from a single charger.

Unfortunately, due to a miscalculation in spatial geometry, getting the box into the space where I want it might require either a teleporter or a sawzall. The space itself is more than big enough for the box, but the opening to that space is not. I'm going to have to disassemble pretty much all the non-fiberglass bulkheads in order to make it fit. Probably time I redesigned that area anyway.

I ordered all drive train parts today. Hopefully I'll get them by the weekend so I can start that process. I have a fairly good idea as to how I'm going to situate everything in the engine compartment. Just not sure what I'm going to do with all the leftover space.
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Last edited by Captain Canuck; 02-18-2019 at 10:13 AM.
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post #157 of 282 Old 02-20-2019
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Re: Electric Conversion log for Kahleesea

I was just involved in a spirited (and polite by the most part) debate over 12 vs 24 vs 48 Vdc marine electrical systems that may be applicable to some extent to your project.

12 vs 24 vs 48 Vdc Marine Electrical Systems

So here is my position, based on 40+ years of experience in various industries, designing, developing, installing, troubleshooting, repairing and marketing electrical products and systems, for the average ICE propelled rec cruising boat from 20 to 50 ft:

1. 48 Vdc is more prone to arcing and damaging contacts than 12 Vdc.

2. Damaged, arced contacts may cause a high Z connection.

3. High Z connections can heat up and cause fires.

4. 12 Vdc high Z connections, though less likely to occur, are more likely to manifest themselves easily (by improper load operation), prompting the boater to investigate and repair the problem before a fire ignites.

5. Receiving an electric shock is likely when contacting 48 Vdc, and unlikely at 12 Vdc.

6. While the 48 Vdc shock itself is not likely to be lethal, the involuntary instinctive response to electric shock can very well be more dangerous than the shock itself (e.g. jerk hand back into rotating machinery).

7. Most marine electrical products rated for 48 Vdc are more expensive.

8. Using 48 Vdc to reduce cable and connector size, may save some money, but will increase impedance, making the installation less safe.

9. From a builder standpoint, one has to calculate the cost / weight savings in cable gauge reduction against the cost / weight increase of the 48 Vdc breakers, switches, electrical products, etc.

10. From a modification standpoint, for up to a 3 kW moderate duration load (e.g. inverter) and a 6 kW temporary load (e.g. thruster) changing system voltage (even locally) is rarely worth the cable size reduction advantage. (I have evaluated many.)

11. For higher loads of longer duration, regardless of DC system voltage, the same power will be required, the battery bank will have to be very large, and it will be discharged rapidly, requiring ICE generator re-charging in most cases, that could have simply been used to power the appliance(s) in the first place, reducing the high stress on the batteries and electrical circuits.

12. Developing a high load, high voltage DC system, and using a DC-DC converter to power safety equipment, introduces a potential single point of failure node, that could render all 12 Vdc safety and nav equipment and lighting inoperable.

13. Below 50 ft LOA, a 12 Vdc electrical system in conjunction with a proper corresponding AC system, will provide excellent service, providing the best compromise between cost, weight, safety, reliability, ease of use, maintenance.

14. In the case of an electric propulsion system, being a > 3 kW and long duration load, a higher voltage DC electrical system is justified.

This system should be completely isolated from the vessel 12 vdc system, the latter having it's own charging systems, to ensure multiple charging source redundancy assuring power availability to all safety equipment in the event the propulsion electrical system (or DC-DC converter) fails.

14. All of these same principles hold true for a 12 Vdc vs 24 Vdc decision. (The electrical product costs will be closer but so will the cable and connector cost.)

15. Above about 50 ft, a 24 Vdc primary electrical system may be justified for a new build.

16. Above about 50 ft, a 24 Vdc local electrical system may be justified for a modification such as a windlass or thruster.

17. Some will propose a design solution they feel is more exciting for them to develop, rather than follow more traditional and proven solutions that are better justified by safety, reliability, life expectancy, and cost.

18. Everyone is absolutely free to disagree with these statements, and do as they wish on their boat. But if you make poor decisions that end up in property damage or personal injury, for you or your loved ones, hold YOURSELF personally accountable, and please don't park your vessel near mine. ;-)

We may all disagree on some or all points, but that's OK, as long as we treat one another with respect, and keep the best interest of forum members

[Disrespectful part edited out. Please get the message]

Last edited by MarkofSeaLife; 02-20-2019 at 03:38 PM.
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post #158 of 282 Old 02-20-2019
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Re: Electric Conversion log for Kahleesea

My boat is very small compared to what youíre talking about, just 22í with a trolling motor for propulsion.

I use two group 31 batteries in series to make a 24v battery bank. For AC charging I have a ProMariner ProSport charger that charges each battery separately. I have a 24v Genasun solar controller that charges them together as a unit.

The rest of the boat is 12v, powered from a Victron 24-12 DC-to-DC converter. A nice side effect of this setup is that the house power is alway 12.5v, no matter how high or low the actual battery bank is.

Catalina 22
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Re: Electric Conversion log for Kahleesea

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My boat is very small compared to what youíre talking about, just 22í with a trolling motor for propulsion.

I use two group 31 batteries in series to make a 24v battery bank. For AC charging I have a ProMariner ProSport charger that charges each battery separately. I have a 24v Genasun solar controller that charges them together as a unit.

The rest of the boat is 12v, powered from a Victron 24-12 DC-to-DC converter. A nice side effect of this setup is that the house power is alway 12.5v, no matter how high or low the actual battery bank is.
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.)
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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.)

This charger connects to each battery separately (I attached the wiring diagram):
ProMariner ProSport 12

Multiple redundancy would be great, but I'm on a Catalina 22, it's not like I'm crossing the Gulf Stream on my way to Bermuda. If the DC-DC converter should go out it would just take a couple minutes to re-connect the house system directly to one of the batteries.

Voltage is high while charging and lower when under heavy load. That mostyly doesn't matter since things designed to run on 12v are designed to run over a range of voltages. But still, my house is always 12.5v. Not a big deal, but a nice side effect.


Again, I'm on a small weekender with much different needs than a larger cruising boat. I just thought I'd throw out what's working for me.
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