Electric Conversion log for Kahleesea - Page 10 - SailNet Community
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post #91 of 268 Old 01-10-2019 Thread Starter
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Re: Electric Conversion log for Kahleesea

Update, 1/10/2019

I've been researching ABYC standards. Guess what? I can't find any pertaining to Lithium batteries. Not even a mention.

I also looked into ABYC wiring standards. None of the charts I can find go any higher than 32VDC. I even downloaded the wire sizing app and it also only goes to 32V. I guess I'll have to rely on IEEE to size my wiring.

If anyone has information to the contrary, I'd love to see it.

Not the result I was expecting when I started researching this part of it.

All the online calcs and charts I see tell me that as long as I stay under 195A, 00 cable is fine. This means staying under ~9kW of current. This is probably fine. I don't expect to run that hot normally anyway.

I also discovered that thunderstruck has a kit that integrates the ME1115 motor. While I could build the exact same system for less, it will save me a lot of time to just buy their kit, so I'll probably just do that. But that's later. Right now, I'm focused on figuring out how to fit the batteries into the available space.

Some other stuff I discovered about Lithium batteries -

Charging when below 0C is not recommended. (not an issue, as I won't be sailing in freezing weather)
The thermal runaway temperature is about 250C. It would take a cascade of failures for this to ever happen. Both the BMS and charger would both have to fail very specifically for the batteries to ever get to this point. However, I can see someone trying to use a lithium battery as a drop-in replacement for a lead acid having this problem. The chargers are NOT compatible.
Overcharging the batteries will kill them quickly. I'll be monitoring the smart charger to make sure it stops at the appropriate voltage. I won't have a BMS system until I build it. Another fun project! Wohoo!
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post #92 of 268 Old 01-11-2019
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Re: Electric Conversion log for Kahleesea

Quote:
Originally Posted by Captain Canuck View Post
Update, 1/10/2019

I've been researching ABYC standards. Guess what? I can't find any pertaining to Lithium batteries. Not even a mention.

I also looked into ABYC wiring standards. None of the charts I can find go any higher than 32VDC. I even downloaded the wire sizing app and it also only goes to 32V. I guess I'll have to rely on IEEE to size my wiring.

If anyone has information to the contrary, I'd love to see it.
ABYC E10 - Storage Batteries - defines that Lithium Ion batteries must be installed in accordance with manufacturers instructions.

ABYC E11 - AC & DC Electrical Systems on boats, applies to DC circuits up to 50 Vdc, and defines minimum cable ampacity (Tables 6A and 6B) and defines that for motor loads, cables need to meet or exceed device manufacturer recommendations. (Most marine motor manufacturers will specify the maximum voltage drop acceptable.)

ABYC E11 also references a number of other standards and codes that may be applicable to your design.

- Title 33, CFR 183 Subpart I
- E-30, Electric Propulsion Systems, (60Vdc + nominal)
- NFPA -70 The National Electrical Code
- SAE J1127, Battery Cable
- UL 1426, Cables for Boats
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Re: Electric Conversion log for Kahleesea

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Originally Posted by boatsurgeon View Post
ABYC E10 - Storage Batteries - defines that Lithium Ion batteries must be installed in accordance with manufacturers instructions.

ABYC E11 - AC & DC Electrical Systems on boats, applies to DC circuits up to 50 Vdc, and defines minimum cable ampacity (Tables 6A and 6B) and defines that for motor loads, cables need to meet or exceed device manufacturer recommendations. (Most marine motor manufacturers will specify the maximum voltage drop acceptable.)

ABYC E11 also references a number of other standards and codes that may be applicable to your design.

- Title 33, CFR 183 Subpart I
- E-30, Electric Propulsion Systems, (60Vdc + nominal)
- NFPA -70 The National Electrical Code
- SAE J1127, Battery Cable
- UL 1426, Cables for Boats
So ABYC has no idea how to deal with lithium batteries, so they're letting manufacturers make those decisions for them. What could possibly go wrong? Maybe I should write and submit a white paper for ABYC once I'm done, giving specific recommendations.

The E30 standard is 10 years old. Technology has advanced tremendously in this area in that time. I don't even think EV-sized lithium batteries were even available at that point, or if they were, they were insanely expensive. With the people starting to use lithium for house batteries, an update is desperately needed.

I found the 6a and 6b ampacity charts. There was no mention of voltage, so I looked elsewhere, assuming they were for 12v systems. If they're good up to 50v, then I'm fine. Nominal charge on the batteries is a bit more than that, but not enough to make any difference. Thanks for that.

This is my first time building something that was so far ahead of the curve that the regulations haven't yet caught up. Fun times!
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Re: Electric Conversion log for Kahleesea

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I haven't reviewed your installation in a while but I believe you are running 4 12v batteries in series. Each 12v battery consists of 6 2v nominal cells that when charged are a touch over 2.1v.

Likelyhood is that one cell has had crumbling lead antimony plates that may or may not have shorted together in the bottom of the battery, resulting in low charge capacity or effectively no capacity.

The other cells (not just in the one battery but in the entire string) are driving current through the bad cell. When the bad cell's limited capacity is exhausted, the rest of the battery will drive the cell into reverse (Think of it as charging the cell backwards. at 46 volts). This further damages the plates in the cell, causes electrolysis and offgassing and generates heat. The cell, instead of being a producer in the circuit, has now become a consumer/resistor. Further more, once the cell is in full short, when you charge your whole bank you wind up OVER charging the rest of the cells to make up the bad cell's lack. You're in a better position than most LA/SLA users with individual battery voltage monitoring, Mike, so at least you can catch this.

Will it catch on fire and burn your boat down? EHHhhhh... depends on the exact nature (impedance of the short), the current being driven through it and time, probably not in the very short term. But at the high currents used in electric propulsion it would scare the crap out of me. <-- disclaimer, BS is going to say that i'm giving you bad advice and am trying to kill you with that statement. I'm just saying what you saw; you were able to continue under gen assisted motoring and get back to harbor without a fire. But I'd be as uncomfortable with the situation as you clearly are so, all good.

Sean
Thanks for explaining in the detail of what may be happening. The boat is on land for the winter back on Long Island and I'm in the Maldives on an eight day charter. Briefly currently there is no load on the battery bank . My 48 volt solar panels are keeping things charged and I usually head to the boat every few weeks and use the Dual Pro 4 charger as you mentioned to charge the batteries up. Since they charge each individual battery in the string I'm not to concerned about over charging the bank.. But, the suspect battery will be replaced in the spring once things warm up. Ironically the suspect battery charges up the same as the others but, it's capacity is short lived as your analysis appears spot on.

Mike
Currently: Enjoying Summer's sailing season

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Re: Electric Conversion log for Kahleesea

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The battery was either not charging as rapidly as others, or discharging more rapidly than others, or both.

Though rare under normal circumstances, because all bats were same age, and we suspect this battery was subject to physical abuse, I would suspect a shorted cell.

This is very frightening. (Could lead to thermal runaway which can cause a whole lot of hurt.)

My recommendation would be to not turn on any charging source, and get that battery out of the circuit ASAP.

The battery should be inspected for bulging sides.

If so, scrap.

If not, take it to a battery shop, or try to charge on it's own, fully, with a relatively low capacity charger.

If it gases like crazy, at a relatively low charge voltage / current, without accepting charge, this confirms a shorted cell and it's toast.



Well, the bank voltage would have continued to decrease.

If the voltage of the remaining bank became too low, some voltage sensitive devices could likely start dropping out.

By turning on the charger, the bank voltage was increased, masking the problem. Again, disconnecting the battery would have been my recommendation.



Could have, leading to thermal runaway, exacerbated by turning the charger on (increasing current flow).
Thanks for the response! The battery will be replaced soon as things warm up. Its under no load for the winter storage but, oddly charges up the same as the other batteries in the string using a Dual Pro 4 charger where each individual battery in the string has it's own charger with the proper AGM profile. But, before I pull the battery I'll do a load test and check the internal resistance to see how it compares with the others in the string out of curiosity. I expect there will be a big discrepancy between it and the other batteries in the string.

Mike
Currently: Enjoying Summer's sailing season

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Re: Electric Conversion log for Kahleesea

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I'm in the Maldives on an eight day charter.
You lucky bastard. Have a great time.
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Re: Electric Conversion log for Kahleesea

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You lucky bastard. Have a great time.
Thanks! But, luck had nothing to do with it. I do however have a special plastic card in my wallet that allows me to do magical things. But, the magic only lasts about a month.

Mike
Currently: Enjoying Summer's sailing season

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Re: Electric Conversion log for Kahleesea

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Thanks! But, luck had nothing to do with it. I do however have a special plastic card in my wallet that allows me to do magical things. But, the magic only lasts about a month.
Indeed, Master Card, Lady Visa and Sir Amex are magical, alas, their magic is limited.

What kind of boat are you chartering?
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Re: Electric Conversion log for Kahleesea

Mike, the Fiance, myself, and the (power boat) couple from the neighboring slip at the local lake are doing 2 weeks in the BVIs in May on a SO 41 DS -- where we intend on finding the right beach and getting married.

I love the magic plastic... hope you're having a blast!

Sean
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Re: Electric Conversion log for Kahleesea

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Mike, the Fiance, myself, and the (power boat) couple from the neighboring slip at the local lake are doing 2 weeks in the BVIs in May on a SO 41 DS -- where we intend on finding the right beach and getting married.

I love the magic plastic... hope you're having a blast!

Sean
Congratulations!! I hope all goes well!
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