AGM Battery - Very Hot and Sulfur Smell

[mbianka]

Originally Posted by goboatingnow

AGMs really have no place on a boat, see the many posts on them elsewhere IMHO

dave

I have a 10kw AGM bank that has been powering my electric propulsion system going on for six years now. I think most problems with AGM's are charging related and not the fault of the batteries themselves.

[goboatingnow]

Originally Posted by mbianka

I have a 10kw AGM bank that has been powering my electric propulsion system going on for six years now. I think most problems with AGM's are charging related and not the fault of the batteries themselves.

Ogh there's nothing wrong with the batteries per say , its just that they have good characteristics that generally can't be exploited on a typical boat , and bad characteristics that do affect the situation.

Nothing wrong with them , bad engineering fit. ( or more correctly poorly speced )

Dave

[colemj]

Originally Posted by Guy

Could you live with a vented battery inside the cabin?

We live with 6 of them right in the main saloon. There really is no significant or noticeable gassing, and absolutely no smell. If these are occurring, you have larger problems than your battery location.

Where did boats put their batteries before AGM's?

Mark

[skipmac]

Originally Posted by goboatingnow

They contain advantageous that can't be utilised and disadvantageous that unfortunately materialise

Dave

As I understand the technology, AGMs can take a much faster charge than FLA batteries so save much charging time on your engine or running a generator to power the charger. The downside is they need to be fully charged on a fairly regular basis and if they aren't will suffer loss of capacity and/or early death.

So in real world terms, if you keep your boat at the dock a lot of the time and can keep the AGMs topped off on a regular basis between trips off the grid then they could be great. If you are usually off the grid and try to live in the 50% to 80% charge range that is common with a lot of cruisers then your AGMs may die young which, considering the cost, would be annoying.\

For me, for now, I will stick with FLA batteries but I can see LiFePO in my future unless something better comes along in the meantime.

[HopCar]

My house batteries lay on their side. Wet batteries wouldn't be a good idea. I think I'll stick with AGM or Gel.

[skipmac]

Originally Posted by HopCar

My house batteries lay on their side. Wet batteries wouldn't be a good idea. I think I'll stick with AGM or Gel.

Why not lay them on their side? After all, what harm can a little acid leak do to a boat?

[colemj]

Originally Posted by skipmac

The downside is they need to be fully charged on a fairly regular basis and if they aren't will suffer loss of capacity and/or early death.

The key words there are "fully" and "regular". Fully means 100% and regular means every day. Very few cruising boats have this capability. The AGM marketing really oversold these into this market.

I am constantly amazed by EVERYONE we meet with AGM's having either only a portion of their capacity remaining on newish batteries or facing a mostly dead bank after 1-2 years. AND REPLACING THEM WITH AGM's AGAIN!!!

I can tell the boats with AGM's simply by how much they are running their diesel/gas generators in tandem with their solar and wind. They are always charging their batteries. When I talk to them, they claim that their batteries go down to 11.8-12.1V several times a day and need to be brought back up. On banks less than 3yr old - some almost brand new. All the while, these people are telling me how great their AGM's are and how they would never have any other type of battery!

So I agree that AGM's have almost no place on a cruising boat unless one is severely limited to mounting location and access. There, gels may be a better option.

Mark

[colemj]

Originally Posted by HopCar

My house batteries lay on their side. Wet batteries wouldn't be a good idea. I think I'll stick with AGM or Gel.

You have a good application for AGM's - a powerboat that produces charge whenever in operation and a dock to come back to regularly.

Mark

[CarlF]

Skipmac gives a good summary of AGM challenges. I recently had a 800AH set of AGMs batteries fail after four years despite a lot of time hooked to shore power and a lot of care (never below 50%, charged at 14.5v temperature compensated etc.). When they failed, it happened over a few weeks not the slow loss of capacity I've experienced with other batteries.

So I went back to gels which I'd used on my previous boat and were going strong after eight years. While the AGM's have a higher charge acceptance rate, they must be charged to 100% or their life is shortened. This takes much longer than charging the lower acceptance rate gels to 90%

AGM's (including the spiral type) are outstanding as engine start batteries where they are not deep cycled.

Carl

[colemj]

The charge acceptance rates are a marketing red herring for most cruising boats, as they cannot supply sufficient charge current to satisfy these rates. Many cannot even supply enough to hit flooded LA battery rates. For example, your 800Ah bank can take 400 or more amps during bulk. I'll go out on a limb and say that you probably do not have a 400A charging source on board...

Mark

[HopCar]

"So I agree that AGM's have almost no place on a cruising boat unless one is severely limited to mounting location and access. There, gels may be a better option."
"You have a good application for AGM's - a powerboat that produces charge whenever in operation and a dock to come back to regularly."

Mark I've actually been thinking of replacing my current AGMs with Gels when the AGMs go bad. My first set of batteries were German made gels and I was very happy with them.

Why do you think gels are better than AGM?

[cal40john]

Originally Posted by HopCar

"So I agree that AGM's have almost no place on a cruising boat unless one is severely limited to mounting location and access. There, gels may be a better option."
"You have a good application for AGM's - a powerboat that produces charge whenever in operation and a dock to come back to regularly."

Mark I've actually been thinking of replacing my current AGMs with Gels when the AGMs go bad. My first set of batteries were German made gels and I was very happy with them.

Why do you think gels are better than AGM?

Here's Deka's take. Gels have some advantages for some cruisers:

http://www.dekabatteries.com/assets/base/1081.pdf

[colemj]

Originally Posted by HopCar

Why do you think gels are better than AGM?

Gels are more tolerant of being discharged and used as cruising boats use them, but less tolerant in charging voltages.

Again, your application is perfect for AGM's, and you would not have to change your charging regime or worry about overcharging.

Mark

[VVD]

Thank you all for your replies and help. We have been quite busy with our electrical problems which have gotten worse. So here's an update. We appreciate any input.

The bad battery was taken out as soon as we noticed it was boiling. Its shaped has changed and unfortunately the other batteries' shape has also changed. At this point, it is clear that our batteries need to be changed and will be.

In addition to this, we measured the output voltage on the alternator and it indicates 15.5V, which is obviously too high. We assume it has an internal regulator and will have the alternator checked and repaired or changed if needed. The alternator is now disconnected and we have been charging our batteries with our generator only. We do not have any solar panel or wind vane.

We wonder about the following:
- We have an external regulator (Balmar max charge). Shouldn't it have picked up the high output of 15.5V?
- Does the regulator measure the output or only the batteries charge and adjust Amps when the batteries reach the set Voltage?
- Until yesterday our batteries were dying but holding in at around 12.05V. Last night, they went down all the way to 10.5V. What could have triggered this additional deterioration? Is it normal or does it indicate we could have an additional problem?
- We want to make sure that we rule out any other issues, especially since we will install new batteries. Our main two worries are
1) A ground leak and we will look for it. Any advice?
2) A short (but I assume we would then see Amps going out right?)

Thanks a lot for your help!
Vincent and Celine

[colemj]

Why do you assume a short or leak? It sounds like over-voltage from the regulator damaged the entire bank. AGM's are less tolerant of this, particularly if it was happening for a while.

You stated that you assumed the alternator is internally regulated then said you had an external regulator?

Did you measure the alternator output on the battery itself? The regulator measures the voltage at the sense wire. If that wire is connected back to the alternator output, then it measures there. If is connected at the battery terminal, then it measures there. That is why I asked the first question - if you are measuring at the alternator output terminal, it is possible that you have sufficient voltage drop in the battery cable to cause a 15.5V output.

If the regulator failed, then it will not have control over the alternator voltage output anymore.

Mark