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Old 04-02-2014, 10:37   #61
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Re: Danger Warning ACR's

Quote:
Originally Posted by FlyingCloud1937 View Post
...A properly temp compensated charge source will reduces the charge voltage, to 3/tenths a volt, less then that of the battery's current acceptance.....
Not quite sure I understand this - do you mean reduce the charge voltage BY 3/10ths of a volt? There is a lot I haven't understood in your postings, and I am an electrical engineer with 45 years experience.

You talk about the need for "Smart Chargers" with temperature compensation. But temperature compensation on a charger is a linear function - reducing the voltage at the rate of about 30mV per cell per 10°C rise in temperature. So at 50C the absorption voltage will be about 13.8v, even in float mode it could be 12.5 volt - both well above the battery voltage of 10 volts where one cell is shorted. So temperature compensation is not going to limit the thermal runaway on a faulty battery, even if the temperature sensor is on the faulty battery.

I asked the question way back in this thread - is there any charger (apart from the Balmar battery to battery Duo Charger) that will
cut its charging voltage completely with very high temperatures. If not there is no way to limit say a house battery exploding if directly connected to a high current charger.
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Old 04-02-2014, 13:44   #62
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Danger Warning ACR's

My shore power charger is a Iota 60 amp (no temp compensation) attached to a 4 x 6V house bank, with start battery connected via an ACR. This discussion has me wondering if I should disconnect the Iota in the off season, in lieu of a small (1.5 amp) Battery Tender.
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Old 04-02-2014, 13:46   #63
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Re: Danger Warning ACR's

Ok Guys,

What I reported is an actual case. The situation was one distant battery micro shorting which finally cascaded into full failure.

Here are more facts.

The house bank located under the wheelhouse forward is 6 L-16's connected to an Magnum 2812 Inverter Charger. The install is about 2 years old.

The start batteries are 4yo 8-D Dynos cranking bats. One for each engine, and are isolted from each other. These are located in the engine room, which is aft under the under the cockpit. The engines are then run through v-drives. The distance between the start and house bank is about 25 feet.

Each engine has an alternator feeding the house bank. There are no shore power chargers or alternators on the start batteries.

The ACR's are Blue Seas BatteryLink™ Automatic Charging Relay PN 7611. Located at the main bus at the house bank.

The fault in the battery caused the incident, as I original wrote. The ACR allowed the fault to cascade. It had no way to stop it until the battery finally exploded. Due to the fact the the fault started as micro shorting of the start battery, causing undue current to flow.

My point is that had the start battery been connected by the Balmar Duo-Charge with temp sensor instead. We would have ended with a failed battery as opposed to a catastrophic failure of the said battery.

IT'S THAT SIMPLE.

I will not install a battery charge system that is not temp compensated. especially in this situation. In this case the engine room while under way is likely approaching 100F plus, the house bats are going to be at least 40F lower temp.

I have the luxury of turning down work. So if an owner won't accept my design then I happily invite them to find another Marine Electrician.

And yes Main Sail, I am against using ACR's, and or any other of the distant bank charging regimes, that lack temp compensation.

Lloyd
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Old 04-02-2014, 14:16   #64
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Re: Danger Warning ACR's

What do you recommend or like to use for a house charger then? Any specific brand or model that protects all the batteries in the house bank? Or do you accomplish this another way? Thanks for any input.
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Old 04-02-2014, 18:06   #65
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Re: Danger Warning ACR's

I don't often install just a charger to the house bank, in fact it's been years. My first choice of charger only is the Newmar Phase Three Charger.

I did install a Pro Mariner on a 30 foot Thompson day cruiser. It not really a house bank, just provides lights, and stereo.

Lloyd



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Originally Posted by ontherocks83 View Post
What do you recommend or like to use for a house charger then? Any specific brand or model that protects all the batteries in the house bank? Or do you accomplish this another way? Thanks for any input.
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Old 04-02-2014, 19:15   #66
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Re: Danger Warning ACR's

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Originally Posted by FlyingCloud1937 View Post
My point is that had the start battery been connected by the Balmar Duo-Charge with temp sensor instead. We would have ended with a failed battery as opposed to a catastrophic failure of the said battery.
Ok, I'll give you that one: there's one battery, with a dedicated Duo-Charge, with temp sensor. I assume the other start battery would have it's own Dual-Charge.

The Duo-Charge actually stops charging when the battery overheats

But what about the house batteries… no solution for that I'm afraid…
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Old 05-02-2014, 01:00   #67
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Re: Danger Warning ACR's

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Originally Posted by s/v Jedi View Post
Ok, I'll give you that one: there's one battery, with a dedicated Duo-Charge, with temp sensor. I assume the other start battery would have it's own Dual-Charge.

The Duo-Charge actually stops charging when the battery overheats

But what about the house batteries… no solution for that I'm afraid…
Maybe what Lloyd is really trying to say is that he's against he architecture of connecting in a remote bank in parallel for charging. Not the ACR per se, although this seems to be a pet peeve of his.

I think we can all agree with him there -- of course it's not good to have another bank, especially in a different place, at a different temperature, getting charged by the same source. That's not really the cause of the problem he described, but it's not good, and I agree with him at least to that extent.

All the banks on my boat (three of them) are completely separate, each with its own completely separate charging sources, and without any kind of interconnection whatsoever. I have two alternators on my main engine, one of which (110 amps * 24v school bus alternator) charges the house bank, and the other of which (ordinary Yanmar 12v) charges the engine start battery. The boat's main AC battery charger, a 24v Victron, serves only the house bank.

I have a completely separate Newmar 12v battery charger which maintains the engine start batt. The generator start batt is charged only by the generator's little alternator and has no AC charger, but that seems to work ok (I am rarely on shore power).

In case of some need of emergency starting of the main engine, I keep jumper cables close to hand so that I can jump the main engine off the generator start battery. But since absolutely zero nothing of any kind is connected to the main engine start battery except the main engine, there is almost nothing to go wrong there.

The flaw in my system, as pointed out by Nick, is paralleling of batteries in my house bank, which would melt down an internally shorted battery even if no charger is connected. Oh well.


Somebody really worried about an exploding lead-acid battery from an internal short might devise a simple system with a temperature sensor on every single battery on the boat, connected to some kind of simple controller which would shut down all charging in case of some abnormal temperatures in any one battery. Ordinary temperature control, as pointed out by Nick, will not prevent a battery explosion such as what Lloyd experienced, unless you happen to be lucky and the short happens to occur in the one battery you have the temperature sensor connected to.


Or, one could do as MaineSail suggests -- just don't leave a shore power charger on continuously when one is not on board. If you're on board, your nose is a good detector of this kind of problem. Solar gives a much safer and much better maintenance charge, than continuous shore power charging. And you eliminate stray current problems. This seems like a really good idea to me.


Useful thread!
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Old 06-02-2014, 11:59   #68
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Re: Danger Warning ACR's

As others have said - a very interesting thread - but has it posed more questions than it has answered?

Here's one more question - are there certain types/brands of battery that are more likely to develop cell shorts which will cause thermal runaway and explosion. I ask this because my AGM battery manual says that Lifeline have never seen thermal runaway in one of their AGM batteries (as of 2011).

Does these mean that Gel or AGM batteries are very much less likely to have a cell short because of their construction?

Please - no more one line answers - "AGMs should not be on a boat"!
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Old 06-02-2014, 12:45   #69
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Re: Danger Warning ACR's

I had a cell short once in 15 years of living aboard. It was an 8D gel, and of course it happened at 0300. The result was a failed battery and a fried isolator.
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Old 06-02-2014, 18:31   #70
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Re: Danger Warning ACR's

Most ACRs that I know of have about a 30-60 seconds delay before closing when sensing a higher set voltage point. From my experience, micro shorting occurs in short bursts.

Even if a burst would last longer , the Acr opens as soon as the voltage falls below the set point then resumes the 30-60 sec cycle even if the voltage is high enough.

So it seems really unusual that it is an ACR issue with the unit cutting off then closing every 1/2 minute or so....
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Old 06-02-2014, 20:42   #71
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Re: Danger Warning ACR's

That may be true into a load/no-load. But when a battery starts micro shorting the loads appears as normal, because the micro short into a battery shows up as only current demand.

It's not a fault, just current flowing.

It's not until the battery plates dead short will the voltage sag., or we actually have a fault that causes the fuse to pop.

Lloyd

Quote:
Originally Posted by silverp40 View Post
Most ACRs that I know of have about a 30-60 seconds delay before closing when sensing a higher set voltage point. From my experience, micro shorting occurs in short bursts.

Even if a burst would last longer , the Acr opens as soon as the voltage falls below the set point then resumes the 30-60 sec cycle even if the voltage is high enough.

So it seems really unusual that it is an ACR issue with the unit cutting off then closing every 1/2 minute or so....
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Old 06-02-2014, 20:58   #72
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Re: Danger Warning ACR's

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Originally Posted by sailinglegend View Post
As others have said - a very interesting thread - but has it posed more questions than it has answered?
NO, under the circumstance that I reported. "the fault was one cell in the battery. The ACR allowed current to flow until the, battery finally dead shorted. By this time enough heat and gasses had formed to create the explosion, which breached the battery casing.

Quote:
Here's one more question - are there certain types/brands of battery that are more likely to develop cell shorts which will cause thermal runaway and explosion. I ask this because my AGM battery manual says that Lifeline have never seen thermal runaway in one of their AGM batteries (as of 2011).
True thermal runaway is more likely in GELL and or AGM, and TTPL, only because of the lower internal resitance of the battery design. For thermal melt down we need a fault in one cell of a multi-cell battery.

FLA's are most likely to create a fault.

Only because they are so forgiving. Meaning that an over charge or under charge, an FLA is more then likely to continue working, albeit at reduced capability. A GEL or AGM, most likely will demonstrate failure mode long before.

But FLA keeps on ticking until we have a catastrophic failure.



Quote:
Does these mean that Gel or AGM batteries are very much less likely to have a cell short because of their construction?

Please - no more one line answers - "AGMs should not be on a boat"!
No, it just means the GEL, and AGM are likely to work one day, and then not the next. Long before cell short mode.

Lloyd
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Old 06-02-2014, 21:35   #73
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Re: Danger Warning ACR's

Let me temper that with:

A lead acid is most likely to short with long term abuse.

And AGM, GEL, and TTPL, are more likely to runaway during a Charge Fault. "That is Un-Regulated charge Source".

This is do to the fact the a FLA is an open vent, and the rest are a Restricted Vent.

Lloyd


Quote:
Originally Posted by FlyingCloud1937 View Post
NO, under the circumstance that I reported. "the fault was one cell in the battery. The ACR allowed current to flow until the, battery finally dead shorted. By this time enough heat and gasses had formed to create the explosion, which breached the battery casing.



True thermal runaway is more likely in GELL and or AGM, and TTPL, only because of the lower internal resitance of the battery design. For thermal melt down we need a fault in one cell of a multi-cell battery.

FLA's are most likely to create a fault.

Only because they are so forgiving. Meaning that an over charge or under charge, an FLA is more then likely to continue working, albeit at reduced capability. A GEL or AGM, most likely will demonstrate failure mode long before.

But FLA keeps on ticking until we have a catastrophic failure.





No, it just means the GEL, and AGM are likely to work one day, and then not the next. Long before cell short mode.

Lloyd
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Old 06-02-2014, 23:08   #74
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Re: Danger Warning ACR's

There are a significant percentage of boats with batteries in parallel being charged from a single charger. Probably a significant majority of cruisers have this situation. In most of these installations the charger does not sense the temperature of each and every parallel battery. I don't think any safety agency is advocating this practice is inherently unsafe.

You seem to be saying that using the ACR to parallel batteries is somehow much worse than paralleling batteries with a wire. It would appear to be the same thing as it relates to this failure. The parallel battery would have exploded with a wire or switch just as easily as with the ACR. Therefore, the danger warning in the title is a bit misplaced in my view. If the ACR is a dangerous device then so must be the piece of wire or a switch used to parallel 2 or more batteries.

Asking the ACR to do temperature sensing is not reasonable in my view. Temperature sensing is used to control the charging voltage/current. An ACR can't do that. The charger is designed to fold back when it senses high temperature. It would certainly be a good idea to have a charger that allows multiple temperature sensors, one for each battery. That may have prevented this failure and any others similarly situated.

Maybe there is something the ACR could do that might help. Most (all?) ACR's remain closed even when the charger is at float voltage. The close/open voltage could be based on both charge and differential battery voltage such that once the charger drops back to float charge the ACR would open. It could reclose if the start battery drops a few tenths below the float voltage. In the case of a start battery (the most common usage) there is no great need to float.
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Old 06-02-2014, 23:44   #75
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Re: Danger Warning ACR's

Trans.....dan

You are missing my point.

Here is my original post:
Quote:
Originally Posted by FlyingCloud1937 View Post
Well as of today I have a new reason to continue not installing Automatic Charge Relays.

This morning I went to a call for dead starter battery, an 8-D Dyno 12volt. As soon as I opened the ER hatch, I new what I was going to find. Just by the the smell of Sulfuric Acid.

A shorted cell in the battery caused the battery to explode. The battery was contained in a home made plywood box, that wasn't liquid tight, nor did it have a cover. So acid is everywhere.

Now about my warning.
The battery was being charged by an Automatic Charge Relay. I surmise that one cell in the battery began micro shorting causing undue current to flow, which generated excess heat, and caused further degradation until we now had an 11 volt nominal battery, which caused more current to flow, until the battery blew.

That's exactly why I have always installed the Balmar Due-Charge with temp sensing.

Lloyd
This the ACR part of the fault:
Quote:
Evidently you do not fully read, or either didn't understand. I, faulted the ACR circuit, bc it cant distinguish between a micro-short and current draw.

That is not part of the design, it has no temp compensation, so it can't know when the battery is getting warm, there-fore it can't current limit.

Neither in a fault, nor when 2 batteries are located in two separate compartments, with differing temps.
Quote:
The failure is a result of the battery micro-shorting, and the lack of fault tolerance of an ACR circuit.

Every install of an ACR is subject to the same fault that happened in this instance.

The ACR didn't fail, it did what it was designed to do. =Pass current to the 2nd battery to maintain voltage.

When the second battery fails, current will pass up-to the limits of the ACR/Fusing.

The ACR lacks any knowledge of how hot the 2nd battery is, or the voltage. So it does it's job of passing current, to maintain voltage of the system design. Until there is an open circuit.
My solution:
Quote:
Originally Posted by FlyingCloud1937 View Post
Ok Guys,

What I reported is an actual case. The situation was one distant battery micro shorting which finally cascaded into full failure.

Here are more facts.

The house bank located under the wheelhouse forward is 6 L-16's connected to an Magnum 2812 Inverter Charger. The install is about 2 years old.

The start batteries are 4yo 8-D Dynos cranking bats. One for each engine, and are isolted from each other. These are located in the engine room, which is aft under the under the cockpit. The engines are then run through v-drives. The distance between the start and house bank is about 25 feet.

Each engine has an alternator feeding the house bank. There are no shore power chargers or alternators on the start batteries.

The ACR's are Blue Seas BatteryLink™ Automatic Charging Relay PN 7611. Located at the main bus at the house bank.

The fault in the battery caused the incident, as I original wrote. The ACR allowed the fault to cascade. It had no way to stop it until the battery finally exploded. Due to the fact the the fault started as micro shorting of the start battery, causing undue current to flow.

My point is that had the start battery been connected by the Balmar Duo-Charge with temp sensor instead. We would have ended with a failed battery as opposed to a catastrophic failure of the said battery.

IT'S THAT SIMPLE.

I will not install a battery charge system that is not temp compensated. especially in this situation. In this case the engine room while under way is likely approaching 100F plus, the house bats are going to be at least 40F lower temp.

I have the luxury of turning down work. So if an owner won't accept my design then I happily invite them to find another Marine Electrician.

And yes Main Sail, I am against using ACR's, and or any other of the distant bank charging regimes, that lack temp compensation.

Lloyd






Quote:
Originally Posted by transmitterdan View Post
There are a significant percentage of boats with batteries in parallel being charged from a single charger. Probably a significant majority of cruisers have this situation. In most of these installations the charger does not sense the temperature of each and every parallel battery. I don't think any safety agency is advocating this practice is inherently unsafe.

You seem to be saying that using the ACR to parallel batteries is somehow much worse than paralleling batteries with a wire. It would appear to be the same thing as it relates to this failure. The parallel battery would have exploded with a wire or switch just as easily as with the ACR. Therefore, the danger warning in the title is a bit misplaced in my view. If the ACR is a dangerous device then so must be the piece of wire or a switch used to parallel 2 or more batteries.

Asking the ACR to do temperature sensing is not reasonable in my view. Temperature sensing is used to control the charging voltage/current. An ACR can't do that. The charger is designed to fold back when it senses high temperature. It would certainly be a good idea to have a charger that allows multiple temperature sensors, one for each battery. That may have prevented this failure and any others similarly situated.

Maybe there is something the ACR could do that might help. Most (all?) ACR's remain closed even when the charger is at float voltage. The close/open voltage could be based on both charge and differential battery voltage such that once the charger drops back to float charge the ACR would open. It could reclose if the start battery drops a few tenths below the float voltage. In the case of a start battery (the most common usage) there is no great need to float.
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