Danger Warning ACR's

[FlyingCloud1937]

Woops............

[Dockhead]

Originally Posted by FlyingCloud1937

Ok, good story.

Let me make THIS very Clear.

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.

No current can flow between the charge source, and the battery at - 3/10's. So no dissipated heat other then what the battery can produce by its self. The bat will self discharge before it can do much damage.

THE ACR, is a current source, based on the fact the house bank will be typically much larger, and is connected to a charge source of it's own needs.

ie Float Charge, the house charger will act as a power supply, increasing current to maintain the Float Voltage at the house bank. The current will rise to the amount needed to float the house bank.

It could mean as much as 100-200 amps depending on the ACR, and fuses.

Now mind you that the current will be determined by the current demand of the parasite battery...ie the starter bank in this case.

The ACR has no temp compensation, nor voltage regulation...it is a CC source, only regulated by the acceptance of parasitic battery bank. Up to the current limit of the fuse.

Lloyd

OK, but . . .

What difference does it make, that the exploding battery is connected through an ACR, or is just hard-wired into the bank?

None, because the ACR is just a relay. When it's closed, the circuit looks exactly as if the battery is hard-wired into the other bank. The ACR is no kind of current source -- it simply provides the path through which the battery charger makes a circuit with that battery. It's the battery charger, not the ACR, which is the current source.

And the presence of the ACR doesn't make any difference to the amount of current the battery charger puts out. The charger will put out its maximum current, whether it is connected to one battery or 20 batteries, if only the voltage of the system is in the bulk charge range -- correct? This is quite elementary, I think, to the way battery chargers work. So one battery wired into the bank, whether by ACR or by just being hard wired in, which has a shorted cell, is going to "trick" the battery charger into thinking that a bulk charge is still needed, and will trigger full output, which is where the trouble begins.

Temperature compensation would help only if the temperature sensor happens to be attached to the one battery which has the shorted cell. In that case the battery charger will get the data it needs to know not to be "tricked" by the system voltage. But temperture sensors attached to the good batteries won't help, because they will not be accepting any charge at the voltage the bad battery has brought the whole system down to, and hence will not be heating up. So all the charger's energy will be concentrated in the one bad battery, which is why it goes boom. And all this is the same with or without an ACR.

Just as it happend on my boat a couple of years ago -- with no ACR.

To put it another way -- the system voltage is brought down by the one bad battery, tricking the battery charger into putting out a bulk charge. But the good batteries won't accept any charge at that voltage. But the bad battery will accept the charge, because one cell is shorted out, which proportionately increases the voltage per working cell.

So if the system voltage is say 14 volts for a nominal 12 volt system, that is 2.33 volts per cell, well within the bulk phase voltage range and not enough to put any energy into a nearly-charged battery. But the battery with the shorted cell is actually a 10 volt battery with five cells. So for the bad battery, that same 14 volts is a whacking 2.8 volts per cell -- equivalent to 16.8 volts for a normal battery (33.6 volts for us 24-volters). At that voltage, the bad battery will accept any amount of current (and will melt down or blow up). So all the battery charger's energy is concentrated on that one bad battery and -- kaboom.


Again -- broken record warning! -- no difference whatsoever, whether that bad battery is hard-wired in or connected through an ACR. In fact the same thing would happen even if the bad battery is the only battery connected to the charger.

[FlyingCloud1937]

OK,

you win.

but guess what, if the start bat, had a Balmar, temp. compensated parasitic charger in between.

WE WOULD NOT BE HAVING THIS DISCUSSION!

and that's it

so much for unregulated parasitic chargers, ACR's, VSR's, or echo chargers.

POINT BLANK...

Lloyd

Originally Posted by Dockhead

OK, but . . .

What difference does it make, that the exploding battery is connected through an ACR, or is just hard-wired into the bank?

None, because the ACR is just a relay. When it's closed, the circuit looks exactly as if the battery is hard-wired into the other bank. The ACR is no kind of current source -- it simply provides the path through which the battery charger makes a circuit with that battery. It's the battery charger, not the ACR, which is the current source.

And the presence of the ACR doesn't make any difference to the amount of current the battery charger puts out. The charger will put out its maximum current, whether it is connected to one battery or 20 batteries, if only the voltage of the system is in the bulk charge range -- correct? This is quite elementary, I think, to the way battery chargers work. So one battery wired into the bank, whether by ACR or by just being hard wired in, which has a shorted cell, is going to "trick" the battery charger into thinking that a bulk charge is still needed, and will trigger full output, which is where the trouble begins.

Temperature compensation would help only if the temperature sensor happens to be attached to the one battery which has the shorted cell. In that case the battery charger will get the data it needs to know not to be "tricked" by the system voltage. But temperture sensors attached to the good batteries won't help, because they will not be accepting any charge at the voltage the bad battery has brought the whole system down to, and hence will not be heating up. So all the charger's energy will be concentrated in the one bad battery, which is why it goes boom. And all this is the same with or without an ACR.

Just as it happend on my boat a couple of years ago -- with no ACR.

To put it another way -- the system voltage is brought down by the one bad battery, tricking the battery charger into putting out a bulk charge. But the good batteries won't accept any charge at that voltage. But the bad battery will accept the charge, because one cell is shorted out, which proportionately increases the voltage per working cell.

So if the system voltage is say 14 volts for a nominal 12 volt system, that is 2.33 volts per cell, well within the bulk phase voltage range and not enough to put any energy into a nearly-charged battery. But the battery with the shorted cell is actually a 10 volt battery with five cells. So for the bad battery, that same 14 volts is a whacking 2.8 volts per cell -- equivalent to 16.8 volts for a normal battery (33.6 volts for us 24-volters). At that voltage, the bad battery will accept any amount of current (and will melt down or blow up). So all the battery charger's energy is concentrated on that one bad battery and -- kaboom.


Again -- broken record warning! -- no difference whatsoever, whether that bad battery is hard-wired in or connected through an ACR. In fact the same thing would happen even if the bad battery is the only battery connected to the charger.

[s/v Jedi]

Don't forget that temperature compensated chargers typically come with one temperature sensor... you must be lucky to connect it to the one battery with the internal short...

Also, don't forget that all healthy batteries that are connected in parallel, will dump all their charge into the shorted out battery. No charger needed to make this a violent event.

A question was asked about my remark that top installs only use series connected batteries. Imagine an internal short in a 2V cell that is in series with 5 other cells to form a 12V bank; nothing happens, the other cells don't discharge into the shorted cell. The bank voltage goes back to 10V so the charger shuts down.

[Dockhead]

Originally Posted by s/v Jedi

Don't forget that temperature compensated chargers typically come with one temperature sensor... you must be lucky to connect it to the one battery with the internal short...

Also, don't forget that all healthy batteries that are connected in parallel, will dump all their charge into the shorted out battery. No charger needed to make this a violent event.

A question was asked about my remark that top installs only use series connected batteries. Imagine an internal short in a 2V cell that is in series with 5 other cells to form a 12V bank; nothing happens, the other cells don't discharge into the shorted cell. The bank voltage goes back to 10V so the charger shuts down.

Thanks, I understand that now.

My setup is poor, from that point of view. As originally constructed, my boat had two 24v service banks, each made up out of 4 12v batteries. So already paralleled once. I combined these two banks into one, so paralleled twice -- ick. When I replaced my batteries two years ago, I tried hard to find 6v batteries, which would have reduced the paralleling, but couldn't find anything which would fit my battery boxes. I have really excellent, robustly bolted-down and fan-ventilated battery boxes which would have been unrealistic to replace. The 12v Trojans fit perfectly.

So I'll have to live with this through the lives of this set of Trojan batteries. After that, I am sincerely hoping to go to LiFePo batteries, hoping that by that time they will be really well developed, which will change everything anyway.

[FlyingCloud1937]

Jedi, and DOCKHEAD.

What you fail to consider is the distant bank, has a different temp. then the regulated bank.

And yes DOCKHEAD the ACR becomes a CC devise, because the charge regulation of the sensed bank, is the design voltage, if it is temp... compensated, and at design float voltage of 13.2.

The amperage/current required to bring the total bank voltage to 13.2, can result in a cooked distant bank, irrespective of the native bank.

WOW.

Now I am done.

Lloyd

Originally Posted by s/v Jedi

Don't forget that temperature compensated chargers typically come with one temperature sensor... you must be lucky to connect it to the one battery with the internal short...

Also, don't forget that all healthy batteries that are connected in parallel, will dump all their charge into the shorted out battery. No charger needed to make this a violent event.

A question was asked about my remark that top installs only use series connected batteries. Imagine an internal short in a 2V cell that is in series with 5 other cells to form a 12V bank; nothing happens, the other cells don't discharge into the shorted cell. The bank voltage goes back to 10V so the charger shuts down.

[Dockhead]

Originally Posted by FlyingCloud1937

Jedi, and DOCKHEAD.

What you fail to consider is the distant bank, has a different temp. then the regulated bank.

And yes DOCKHEAD the ACR becomes a CC devise, because the charge regulation of the sensed bank, is the design voltage, if it is temp... compensated, and at design float voltage of 13.2.

The amperage/current required to bring the total bank voltage to 13.2, can result in a cooked distant bank, irrespective of the native bank.

WOW.

Now I am done.

Lloyd

Sure, but the difference in temperature between normal batteries is not going to change the charge voltage enough to cook the distant bank. The charger's temperature compensation is a matter of a few tenths of a volt.

In fact, the distant bank is more likely to be undercharged, not cooked, because of the voltage drop over the cables.

And this is not what happened in the scenario in your original post anyway -- you had a shorted cell, just like what happened to me a couple of years ago. Without an ACR.

On top of all of that, what you are describing is anyway not the result of an ACR device -- it's the result of having part of a bank at some distance from the other part of the bank which has the voltage and temperature sensors connected.


By the way, I don't have any temperature sensors connected at all on my boat. 70 amps is only 16% of C for me, so full charger output does not produce any significant temperature rise in my batteries.

[Juniper]

I've had a battery blow up sitting unconnected just in storage before, no charge going in, no wires on it,

[ontherocks83]

Flying,

I find this thread very interesting and informative so as frustrated as you may feel thank you for posting it. I am learning something here from everybody. I do have a question for you and everyone else.

What is your recommended set up? For example I have a 2 battery house bank and one start battery. As of now they are connected to a 2 bank charger and when that is off they are regulated by a 1/2/combo switch. I was very much looking at putting a ECHO charger in and disconnecting the leads to the start battery from the main charger.

Obviously after reading this I am having some concerns/doubts. What would you and all others recommend? I really like the thought of an echo charger so if there is a good way to use one or something similar that would be awesome.

Is there such a thing as a temp sensor you can wire into a electro mechanical switch that would disconnect the echo charger if something like this happens or am I just dreaming?

Thank you all for any and all info

[s/v Jedi]

Originally Posted by FlyingCloud1937

Jedi, and DOCKHEAD.

What you fail to consider is the distant bank, has a different temp. then the regulated bank.

To the contrary. I wrote that the only battery that gets a temperature corrected charging regime, is the one with the temperature sensor connected.

Only during normal operation, one can ASSUME that the temperature of all batteries in one bank is equal. This is what you take as your example I quoted above. But it isn't what we were discussing, you're changing the facts again: there was one battery with an internal short, and that battery will run hot into a thermal shutdown even when you have your temperature corrected charger with it's sensor on a DIFFERENT battery.

How hard is that to understand and acknowledge?

[Maine Sail]

I suspect the title could have read:

Multi-Output Battery Charger Warning

Non-Temp Compensated Battery Charger Warning

Lack Of Battery Temp Sensing Warning

1/2/BOTH Switch Warning

Parallel Battery Bank Warning

Parallel Charging of Batteries Warning

Diode Isolator Warning

Alternator Charging Warning

Solar Charging Warning

Improper Battery Maintenance Warning

Improper Battery Installation & Maintenance Warning

Unattended Charging Warning

Large Current Source Unattended Charging Warning

However we know from previous posts by Lloyd that he is not a fan of ACR/VSR/combiners thus I suspect his wording was just from his gut feelings on the concept of ACR's? I don't think it was intentional, though maybe it was....

Perhaps the real issue here is that MOST battery chargers, even ones with built in temp compensation, allow for just ONE temp sensor. How do you know which battery will be the one to internally short..?? How does a multi-output charger protect all the outputs with only one sensor? Why don't more charger manufactures provide temp sensors for each output? Why don't most allow for more than one sensor? This can be a topic unto its own.

If that charger had multiple temp sensors, as it really should IMHO, it could have stopped charging when the AUX battery got to hot or dialed back voltage dramatically. The ACR would have done its job, isolated the banks, and no issues. Keep in mind that temp sensing only works when the battery is hot, once it cools down you get your current back and the process repeats......

Consider these points too:

** The vast majority of boats in the US use paralleled batteries thus creating the SAME issue even without an ACR.

** The vast majority of battery chargers used on boats have NO temp compensation hooked up, even when the charger has a port for it and this can create the SAME issue.

** Almost every charger I know of has only ONE temp sensor, especially reasonably priced models.. Every manufacturer I have spoken with says NOT to combine them or add more temp sensors. This can create the SAME issue.

** Any multi-output battery charger can create the SAME issue.

** A diode isolator can create the SAME issue..

** The vast majority of boats in this country run internally regulated alternators and these, can again, create the SAME issue.

** The vast majority of boats in this country still use a 1/2/BOTH switch and owners charge using the BOTH setting. This can create the SAME issue.

** The vast majority of external regulators i see installed are installed without battery temp compensation. This can create the SAME issue. About 4 in 10 external regs I see are not wired for batt temp..

** The vast majority of solar controllers installed on boats have no temp compensation installed and could create the SAME issue too, with enough array. Even when they do have temp compensation it is wired to ONE battery in the bank.



The real issue here, as I see it, is lack of owner maintenance, proper upkeep & regular testing of his battery bank... It was also a horrendous installation.

Batteries being in an engine room is also unwise due to heat which goes back to the an increased need for temp compensation (the real issue). Even with temp compensation batteries in hot areas still lead abusive lives and die considerably sooner.

I am personally not a fan of unattended charging by any large current source and much prefer the low current of solar, even at a dock. Even with temp compensation I have seen far too many chargers and inverter/chargers go "tits up" and ruin batteries.

Yes, the Duo Charger is a great tool but unfortunately they represent about .2% (warning: made up stat based on my observations) of the way folks charge AUX batteries in this country... I see about 9:1 Echo's or ACR/VSR/Combiners to Duo Chargers..... Luckily diode idolaters are disappearing but the still represent a significantly larger chunk of the market than does the Duo..

Let's not miss the forest for the trees, Lloyd brings up a very good topic!!!

I just feel the way it was presented, singling out the ACR, can be seen or taken by some as a tad misleading, especially when there are dozens of other situations where you would have the same exact outcome..

IMHO the topic could have been better presented if come at based on lack of maintenance or lack of temp compensation because this applies to hundreds of thousands of boats out there including Lloyd's..

Unfortunately nothing is fool proof....

Perhaps someone can clear up for me how one bank, in parallel, can be at 11 volts, and a VSR, which cuts out at about 12.85V to 13.0V would remain connected...? That one has me stumped...

If the banks are in parallel, and one batt is at 11V, there is no ACR connection for very long, unless someone re-wrote Ohm's Law while I was sleeping.......

You could get relay cycling but not a constant parallel connection if one bank remains below the combine voltage.....

I suspect the large current source was able to hold the batts, even with the short, at combine levels and that one battery was not at 11V when the other bank was at combine levels. That can't happen when paralleled...

Most solar arrays would not have had the current to hold a parallel ARC connection into a shorted battery but a 100A+ inverter charger could......

Something to think about when running a 100A plus charge source, continually, to supply 0.4A of current to maintain a bank of batteries at the dock... Personally, from experience, I find that unwise but people love to do it..........

We should keep in mind that a temp sensor will ONLY limit voltage when it is hot.

Follow me here:

Large current source shuts down or drastically limits by temp sensing > shorted battery cools off > large current source kicks back on again > repeat process until battery explodes...

Great topic Lloyd!! I just think some feel you shot the wrong messenger and the topic is actually much wider in scope than just ACR's...

[s/v Jedi]

Originally Posted by Maine Sail

Great topic Lloyd!! I just think some feel you shot the wrong messenger and the topic is much wider in scope than just ACR's...

Exactly!

Once again I find Maine Sail on the same standpoint as myself but using much better wording to bring it over, chappeau!

[btrayfors]

Ontherocks83,

You could use a Balmar DuoCharge device (as mentioned by the OP) in lieu of the Echo Charge. Here's the manual for that device: www.balmar.net/PDF/Duo%20Charge%20Manual.pdf

The DuoCharge costs about twice what the EchoCharge goes for, but it is more sophisticated in that it can be programmed for any battery chemistry and it has a temp sensor option which when activated "cuts off charging current" to the start battery.

Bill

[colemj]

Originally Posted by FlyingCloud1937

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

Lloyd, on our ACR's, if one of the batteries was at 11V, the ACR would not connect and that battery would stay isolated from the charging source.

Mark

[colemj]

Oops, I didn't see that there was a second page to this thread and that Mainesail already mentioned this low voltage disconnect thing.

Also, he mentions something that I think is important - when we are leaving the boat on shore power with the charger always on, I dial back the maximum current on the charger to 10A. This is enough to keep the batteries in float, while minimizing the possibility that something could go very wrong very fast.

Mark