Battery Chargers Misbehaving

[Dockhead]

I came home last night from a rare and splendid dinner in a restaurant to a nasty smell in the boat. I at first thought it was gas, then realized it was boiling batteries (unfortunately, I know that smell from experience).

I am in one of those Swedish harbors where the electricity is metered with a smart card, and after you've consumed your allotment, your shore power is cut off. This happened earlier in the day, just as I had washing machine and other high load consumers going. My system continued to supply these loads from the inverter, so for a few minutes the batteries were supplying this big load, probably around 3000 watts. When I restored shore power, the charger started recharging the batteries again.

I have a 24 volt system, and I have 8 Trojan 24TMX 12 volt batts arranged in 4 pairs. The aft most pair was the hottest, and a couple of the cells had plates exposed from the boiling. I thought -- these are toast -- there's a shorted cell in one of these. I filled all the cells and left it all to cool until the morning.

This morning I got up and tested the batts with my Argus tester. I was surprised to find no shorted cells anywhere, and all batts testing out quite well, down about 25% from their peak capacity, but approximately the same as when the batts were new.

Do Trojan batteries have nine lives? This is the third or fourth really bad incident I've had with them, including two run down dead flat and left for weeks incidents. They are going on four years old and are deep cycled nearly every day since I live aboard, without shore power most of the time. They've done at least 1000 cycles, which is more than their rated life. So I'm charging them and watching to see what will happen.


But the big question is why did they boil, if there's no shorted cell? I can't figure this out. Is it a malfunction of the battery charger? Was the charger spoofed by the short hard discharge, to think that the batteries were flat, when they weren't? It's a Victron Multiplus charger/inverter. Grateful for any insight.

[Dockhead]

I have been charging them now for a few hours, and the charge voltage is now 29.7, the top of the absorption phase.

The batts are bubbling, but there is no heat.

Now why in the world would they have boiled last night?

[a64pilot]

I've had this happen before, I theorize the hard charge cleaned off some sulfation, but that is only theory, however the once or twice it has happened to me, the batteries did not last long, this was their death song. But they were cheaper "Deep cycle" trolling motor batteries used on a fishing boat, not a house bank.
Yes "GOOD" batteries will take more abuse than cheaper batteries. I've stupidly left the master switch on my little airplane, to kill the battery down to the point that it didn't have enough current left to close the relay and it has recovered. It's a Concorde RGVRSLAB, a flooded Gill battery would not have recovered.

It was only one or two cells per battery that boiled out, not the whole battery, right?

[Dockhead]

Originally Posted by a64pilot

I've had this happen before, I theorize the hard charge cleaned off some sulfation, but that is only theory, however the once or twice it has happened to me, the batteries did not last long, this was their death song. But they were cheaper "Deep cycle" trolling motor batteries used on a fishing boat, not a house bank.
Yes "GOOD" batteries will take more abuse than cheaper batteries. I've stupidly left the master switch on my little airplane, to kill the battery down to the point that it didn't have enough current left to close the relay and it has recovered. It's a Concorde RGVRSLAB, a flooded Gill battery would not have recovered.

It was only one or two cells per battery that boiled out, not the whole battery, right?

Yes, it was just a cell or two per battery in a couple of batts which boiled out.

All batteries were warm, which is unusual. The aft four were hot, and the aftmost two were very hot and smoking.

I'm trying to figure out how this would happen. What would make the charger try to pump all this current through? Could low electrolyte in a couple of cells have done it? I had not checked them in a while, so it's possible there were some low cells.

Was it a battery problem or a charger problem? Really puzzled by this one.

[svlamorocha]

Originally Posted by Dockhead

Was the charger spoofed by the short hard discharge, to think that the batteries were flat, when they weren't? It's a Victron Multiplus charger/inverter. Grateful for any insight.

That is where my money is. I suggest you find out what is the algorithm that determines absorption time in your Victron device with the firmware version that it has installed. They can be based on bulk time (probably not a problem this item), voltage before charge starts (which could be a big problem in the scenario you described).

This is the sort of algorithm that could have been spoofed (taken from "Manual - MultiPlus 3k 120V - rev 05 - EN"):

The right amount of charge: variable absorption time
In the event of slight battery discharge, absorption is kept short to prevent overcharging and excessive gas formation. After deep
discharging, the absorption time is automatically extended in order to fully charge the battery.

Note that the same document says that absorption time "depends on bulk time". Do not assume both statements are correct.

If you compound this with a basic algorithm that determines that there is a deep discharge just because voltaeg is low when you turn the charger on, bingo!

Note that the big voltage sag of the flooded batts (as opposed to AGMs) will magnify the issue.

Those "secret" algorithms tend to be less smart that they are said to be. In my experience you have to ask Victron and then test to make sure the device works the way they say it should work. Be prepared to find conflicting answers that arise from successive versions of the firmware

I run the risk of stating what is obvious to you but may not be obvious to everyone. Even in the most expensive systems, the charger typically determines absorption time based on a very rudimentary algorithm that does not take in to account the key variable, which is amps going into the battery as a % of battery capacity. IMHO it is a shame that many boat shave a shunt for the battery monitor but they do not use the info as "input" to the charger.

Please keep us posted.

[Dockhead]

Originally Posted by svlamorocha

That is where my money is. I suggest you find out what is the algorithm that determines absorption time in your Victron device with the firmware version that it has installed. They can be based on bulk time (probably not a problem this item), voltage before charge starts (which could be a big problem in the scenario you described).

This is the sort of algorithm that could have been spoofed (taken from "Manual - MultiPlus 3k 120V - rev 05 - EN"):

The right amount of charge: variable absorption time
In the event of slight battery discharge, absorption is kept short to prevent overcharging and excessive gas formation. After deep
discharging, the absorption time is automatically extended in order to fully charge the battery.

Note that the same document says that absorption time "depends on bulk time". Do not assume both statements are correct.

If you compound this with a basic algorithm that determines that there is a deep discharge just because voltaeg is low when you turn the charger on, bingo!

Note that the big voltage sag of the flooded batts (as opposed to AGMs) will magnify the issue.

Those "secret" algorithms tend to be less smart that they are said to be. In my experience you have to ask Victron and then test to make sure the device works the way they say it should work. Be prepared to find conflicting answers that arise from successive versions of the firmware

I run the risk of stating what is obvious to you but may not be obvious to everyone. Even in the most expensive systems, the charger typically determines absorption time based on a very rudimentary algorithm that does not take in to account the key variable, which is amps going into the battery as a % of battery capacity. IMHO it is a shame that many boat shave a shunt for the battery monitor but they do not use the info as "input" to the charger.

Please keep us posted.

Thanks for the very thoughtful and helpful answer.

But to cut to the chase -- could this problem be caused by too long time at absorption voltage? Will the batts start to actually boil?

If the answer to that is yes, then I have a good idea about how it happened.

Also, my Victron charger often seems to stay on absorption far longer than it is supposed to. Some of these parameters are programmable, and I wonder whether the programming didn't work the way it was supposed, or whether the unit simply malfunctions.

[Dockhead]

It looks like I may have answered my own question.

I had ANOTHER power interruption -- the money ran out on the electronic card thing. No hard discharge this time, and I soon put more money on it.

This seems to have reset the absorption time. Over the course of the afternoon, after some hours of normal-looking absorption charging at 29.7 volts, with normal temperature, the battery temperature started to rise, and the batts were already pretty hot when I overrode the Victron and forced it into float mode.

You do this by switching the digital multi control back and forth between "on" and "charger only" then waiting for the end of the sequences of lights.

It seems to me that the batts can't tolerate more than a certain amount of absorption charging before they start to heat up, and even boil. The Victron charger is not smart enough to understand that five minutes ago (before shore power was briefly interrupted), it was already 3 1/2 hours into a 4 hour absorption cycle, and started all over again. With the result that the batts eventually heat up and boil.

A new lesson for me in lead-acid battery care and feeding? Can anyone confirm this theory?

If this is what happened, then three takeaways:

1. Bloody battery chargers could sure be smarter.

2. Better keep an eye on the duration of absorption charges rather than blindly trusting the charger.

3. Better hook up that temperature sensor, which I never thought was necessary.

[St. Elsewhere]

Originally Posted by Dockhead

I have been charging them now for a few hours, and the charge voltage is now 29.7, the top of the absorption phase.

The batts are bubbling, but there is no heat.

Now why in the world would they have boiled last night?

Why is the charger doing 29.7 volts? I thought that 28.4 was the standard absorption setting for a 24 volt system. Maybe that is why they are gassing.

[jeepbluetj]

Originally Posted by Dockhead

...

1. Bloody battery chargers could sure be smarter.

...

I'll heartily agree with that. I've installed no less than 4 different 'smart' chargers on my dinky little boat. NOCO, ProMariner, etc... All sucked beyond belief - they all were battery boilers. Problem would be that I'd come back into the marina - possibly after motoring back (i.e. full batteries). The chargers would typically then go into bulk (for some amount of time) then 14.4v absorb for hours. And just like what dockhead said, boiled batteries. The promariner I tried NEVER came out of absorb. The only charger I've got that works right is the Midnight Solar Kid controller in my RV. (it has a current sensor to kick it out of absorb)

For the boat, I now do bulk by hand, and just have a little battery tender on there for float. The boat is on shore power most of the time.

[Dockhead]

Originally Posted by jeepbluetj

I'll heartily agree with that. I've installed no less than 4 different 'smart' chargers on my dinky little boat. NOCO, ProMariner, etc... All sucked beyond belief - they all were battery boilers. Problem would be that I'd come back into the marina - possibly after motoring back (i.e. full batteries). The chargers would typically then go into bulk (for some amount of time) then 14.4v absorb for hours. And just like what dockhead said, boiled batteries. The promariner I tried NEVER came out of absorb. The only charger I've got that works right is the Midnight Solar Kid controller in my RV. (it has a current sensor to kick it out of absorb)

For the boat, I now do bulk by hand, and just have a little battery tender on there for float. The boat is on shore power most of the time.

You learn something every bloody day cruising, don't you? It's fun and enriching, but after a certain point you start to feel stupid and incompetent

I have been just trusting my Victron to take care of my batts all these years, and now finally I understand that you can't just do that.

Now finally I know how to find the "switch off absorption and go to float" switch. And I'm going to start using it, too.

[Dockhead]

Originally Posted by St. Elsewhere

Why is the charger doing 29.7 volts? I thought that 28.4 was the standard absorption setting for a 24 volt system. Maybe that is why they are gassing.

Trojan specify 29.6 absorption voltage for their flooded batts, which is what I have.

[svlamorocha]

Originally Posted by St. Elsewhere

Why is the charger doing 29.7 volts? I thought that 28.4 was the standard absorption setting for a 24 volt system. Maybe that is why they are gassing.

28.4V (or 14.2V in a 12V system) is a "safe" setting that will not boil the batteries much even if the thing gets stuck at that voltage for a week. It is one of those "dumb down" decisions made by manufacturers that prefer to kill batteries slowly by undercharging them rather than charging them properly, which required an owner who understands how stuff works. In fact most "standard" settings in pleasure boat charging systems are almost guaranteed to undercharge batteries.. MaineSail has good writeups on this.

Dockhead has stated how long his batteries have lasted with the proper (higher than "standard") settings and that is proof of what the theory says...

C

[GrowleyMonster]

You make a darn good case for MANUALLY charging the batteries, and using a float charger to maintain them when they are only under a small load or none at all. One of the projects on the table for Mr Wiggles is a fully manual 3kva charger using a Variac and a big rectifier on a bigger heat sink, an ammeter and a volt meter. I may add an isolation transformer, too. Manual gives you the capability of an equalizing charge. I am not aware of any "smart" charger that delivers a proper equalizing charge, and equalization demands careful monitoring, anyway. With my Variac based charger I will be able to individually equalize each of my 8 6v batteries and my two 12v house batteries. Or I can do a normal bulk and absorption cycle on either bank. Or a float charge, though I would rather use the isolated smart charger for float charging, for safety reasons. Smart chargers have their flaws and limitations, and are NOT the perfect answer for everyone. A smart charger takes better care of the batteries than some boaters would, yeah. But for those willing to educate themselves on proper charging regimens and willing to take the time to do it, boat owner + manual charger = SMARTER charger.

[Dockhead]

Originally Posted by GrowleyMonster

You make a darn good case for MANUALLY charging the batteries, and using a float charger to maintain them when they are only under a small load or none at all. One of the projects on the table for Mr Wiggles is a fully manual 3kva charger using a Variac and a big rectifier on a bigger heat sink, an ammeter and a volt meter. I may add an isolation transformer, too. Manual gives you the capability of an equalizing charge. I am not aware of any "smart" charger that delivers a proper equalizing charge, and equalization demands careful monitoring, anyway. With my Variac based charger I will be able to individually equalize each of my 8 6v batteries and my two 12v house batteries. Or I can do a normal bulk and absorption cycle on either bank. Or a float charge, though I would rather use the isolated smart charger for float charging, for safety reasons. Smart chargers have their flaws and limitations, and are NOT the perfect answer for everyone. A smart charger takes better care of the batteries than some boaters would, yeah. But for those willing to educate themselves on proper charging regimens and willing to take the time to do it, boat owner + manual charger = SMARTER charger.

I don't know about you, but I would kill my batts in no time with a manual charger No doubt about it. One more thing to remember to turn off before it causes a disaster? Bah! I can't even remember to turn the hose off when filling my water tanks.

I think 99% of us need smart chargers.

I think Victron is probably smart enough for government work (so to speak). It is I who should have been aware that disconnecting and reconnecting shore power would reset the absorption cycle. I didn't even know I could manually put the charger into float mode. Now I know!

[donradcliffe]

Most of the smart chargers and regulators I know of will reset the absorption time if you cycle the AC power or the engine 'ignition'. However, the Xantrex inverter-chargers will cut the absorption cycle based on current flow.

If you live aboard, why don't you cut the programmed absorption time down to say two hours, and manually cycle the charger if you know you need more?

I also agree that 29.7v is really pushing things.