Electric Conversion log for Kahleesea - Page 9 - SailNet Community
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post #81 of 282 Old 01-09-2019
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Re: Electric Conversion log for Kahleesea

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Originally Posted by boatsurgeon View Post
While I personally have no skin in the gain, I find in many cases, DIYers over-estimate their capabilities.
Yes you do have "skin in the game".

Many people who work in the marine industries, as you do, belittle those that own boats.

This appears to be just that.

Yes you do have skin in the game, and, trying to scare boat owners to pay you and other marine businesses to only allow you to work on boats is deceitful.





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post #82 of 282 Old 01-09-2019
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Re: Electric Conversion log for Kahleesea

BS leaves the price tag on supposed 'public service' gift, then adds/informs them about his loss of time and biz...when presenting.
What a.......jeez.....
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post #83 of 282 Old 01-09-2019 Thread Starter
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Re: Electric Conversion log for Kahleesea

Boatsurgeon,

I see what you're saying re: how I've set up temporary boat charging. However, the odds of a healthy AGM battery gassing in sub 50 degree weather while on a 800mA smart charger are pretty much zero, so I'm OK with it.

wsmac,

Cool! Diving is awesome. I didn't even know you could remove a prop while the boat was still in the water. Unfortunately, the Chesapeake Bay is 49 degrees right now, and typically about as clear as tomato soup. Also, diving in a marina is not a safe practice. There are reasons that there are "no swimming" signs around every marina. Sadly, I'll have to wait until they haul me out.
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post #84 of 282 Old 01-09-2019
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Re: Electric Conversion log for Kahleesea

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Originally Posted by boatsurgeon View Post
I apologise if you found my response offensive. It was not intended to be so.

Based on your prior post, it sounded like you were questioning if the first battery in a series string could suffer the same "over-worked" condition as an improperly wired first battery in a parallel string.
My answer was in response to that.
Understood. What I was trying to figure out what was happening internally to the failing battery. Voltage at it's terminals was dropping yet the other batteries in the string were equal. The current from the string was flowing through each battery (as you mentioned) and had to flow through the most positive battery with the dropping voltage. So my questions are:

Was the resistance internally changing dropping the voltage?

What would the end result be if I had not fired up the generator and starting electro sailing?
Would the voltage ultimately drop to zero but, current from the other batteries still be flowing through it?

Or would the failing battery eventually become an open circuit i.e. like a blown fuse. With the pack now providing 0 Volts to the controller?

Hopefully I won't face this situation again once I replace the defective battery. Would like to know your opinion.

Mike
Currently: Enjoying Summer's sailing season

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post #85 of 282 Old 01-09-2019
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Re: Electric Conversion log for Kahleesea

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BS leaves the price tag on supposed 'public service' gift, then adds/informs them about his loss of time and biz...when presenting.
What a.......jeez.....
I'm trying to help people here stay safe.

What are you trying to do?
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Re: Electric Conversion log for Kahleesea

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Was the resistance internally changing dropping the voltage?
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.

Quote:
What would the end result be if I had not fired up the generator and starting electro sailing?
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.

Quote:
Would the voltage ultimately drop to zero but, current from the other batteries still be flowing through it?
Could have, leading to thermal runaway, exacerbated by turning the charger on (increasing current flow).
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Re: Electric Conversion log for Kahleesea

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Originally Posted by Captain Canuck View Post
Boatsurgeon,

I see what you're saying re: how I've set up temporary boat charging. However, the odds of a healthy AGM battery gassing in sub 50 degree weather while on a 800mA smart charger are pretty much zero, so I'm OK with it.
If truly limited to 800 mA, that is a "maintainer", not a "charger".

If it has spring clamps, it is not ABYC compliant.

Even an 800 mA maintainer with spring clamps, can create a spark in a battery compartment.

Any combustible, such as hydrogen gas from a charging battery, gasoline from an improperly stored jerry, stove alcohol from a leaking jug, propane from a canister, tank, or chafed hose, can cause a "kaboom" or fire.

I have had 3 kabooms occur near my personal vessel, at 3 different marinas, caused by people mucking with electrical systems near combustibles.

On one occasion, had I accepted my wife's offer to get hamburgers before leaving the fuel dock, we would have had the guys burning engine compartment lids land on our foredeck. Thankfully, I had minor indigestion, and said, "Nah lets just head out". I over heard the guy say to the dockhand, "Put a hundred in each, no just the port, something is going on." (The idjut new dang well he had a gas leak; what he didn't know is that automotive starters and alternators are not ignition proof.)

On another occasion, leaking DIY propane system install and faulty bilge pump wiring. Had to clean the soot off my decks, 9 others had some real damage, and 3 others including the guy lost their boats completely. The guy had no money and no insurance. His life was ruined that day.

The third occasion, yet another marina, when an unqualified staffer was trying to replace a battery. "Kaboom". Runabout burned to the waterline.

These experiences are in part why I became a "sparky", and try to help boaters keep safe.

If a boater mucks with stuff they don't really know, it isn't just them they are putting at risk, it is everyone who comes aboard, or whose boat is near theirs.

Be safe.
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Re: Electric Conversion log for Kahleesea

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Originally Posted by boatsurgeon View Post
If truly limited to 800 mA, that is a "maintainer", not a "charger".

If it has spring clamps, it is not ABYC compliant.

Even an 800 mA maintainer with spring clamps, can create a spark in a battery compartment.

Any combustible, such as hydrogen gas from a charging battery, gasoline from an improperly stored jerry, stove alcohol from a leaking jug, propane from a canister, tank, or chafed hose, can cause a "kaboom" or fire.
The spark isn't the problem if there's nothing to ignite. This holds true in automotive diagnostics as well.

Unless the battery gasses, which a healthy AGM, charged slowly, won't do. My only other combustion source is the propane tank, which is in it's own isolated compartment, with the valve closed for the winter.

As I said, I'm not concerned. The batteries and charger are coming in soon, So once I figure out how I'm going to place and mount the batteries and bus bars, I can get the 48v-12v converter and install that part of the system in the boat. Then I'll trade all the lead-acid peccadilloes for lithium peccadilloes. Which, to my mind, are much more manageable.
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Re: Electric Conversion log for Kahleesea

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Originally Posted by mbianka View Post
Understood. What I was trying to figure out what was happening internally to the failing battery. Voltage at it's terminals was dropping yet the other batteries in the string were equal. The current from the string was flowing through each battery (as you mentioned) and had to flow through the most positive battery with the dropping voltage. So my questions are:

Was the resistance internally changing dropping the voltage?

What would the end result be if I had not fired up the generator and starting electro sailing?
Would the voltage ultimately drop to zero but, current from the other batteries still be flowing through it?

Or would the failing battery eventually become an open circuit i.e. like a blown fuse. With the pack now providing 0 Volts to the controller?
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
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Re: Electric Conversion log for Kahleesea

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Originally Posted by texlan View Post

<-- 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
Lucky to get away with it, could have gone differently, real bad, real fast.

Not worth the risk to vessel, family, and one's own skin.

My recommendation, get that battery out of the circuit ASAP.

If this series string of batteries had another series string in parallel, it could have been really, really bad.

Last edited by boatsurgeon; 01-10-2019 at 10:20 AM.
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