AGM Battery Failure - Two Sets in Two Years

[mcon12000]

Originally Posted by Bycrick

Another little gotcha on tight terminal nuts. While the bus bar is tinned copper, I think the studs/nuts are stainless. The Blue Sea eBay site didn’t say. But I had one fellow who’d very carefully cleaned the bus bar studs and nuts with solvent. So clean, in fact, that two of the nuts galled on tightening. The nut wouldn’t come off and he broke the studs. But the terminal itself would move.

Here's a fun fact and useful if anyone is debating a dirty stud...

The stud doesn't effect the current carrying capacity of the circuit it's the cable terminals and buss bar itself. So yeah that guy would have been better off leaving it alone.

I edited my original post bc it sounded rude. It wasn't my intention sorry...

[sailjumanji]

Originally Posted by mcon12000

Reading threads like this one from start to finish makes me really happy I'm taking the ABYC certification course right now. I'm far from an expert but I'm reading as much good information here as bad albeit all of it with good intentions.

I gather from the back and forth that you have confirmed that there are no negative wires on the battery side of the shunt? It seems like this has been beat to death but I have to ask because a small load you're unaware of will throw off all your calculations and leave the bank discharged beyond what might be ideal at 40% in this case shortening the service life dramatically.

The tin missing from the buss bar shouldn't be a factor in the short term but if you should replace it while you're pulling your hair out. It was likely an issue prior to you cleaning the area up and it could cause a problem right around the time you forget about it.

I'm not familiar with the charging system you have but it sounds like my victron setup and the comments about multiple charge sources being an issue are misplaced with the newer systems. The exception being the engine alternators so this has me thinking...

1. Your shore charger is intelligent and safe

2. Your MPPT chargers are intelligent and safe

So in theory the house bank is ideally serviced by the shore/generator and the MPPT but the alternators do not have comparable sensing available. Since I'm not sure you can easily add an externally regulated alternator to your outboards can I suggest adding two Victron 30amp DC to DC Chargers to your engine side of the system?

It would eliminate the last possible problem on the charging side and provide a perfect charge while motoring. They solve many problems associated with engine charging of start and house banks. So alternator would charge a start only battery and the DC to DC charger charges the house.

Mine is setup the opposite with an externally regulated alternator charging the house bank directly and the start battery (different chemistry) is charged via the DC charger.

You seem to be all over this so I'm just throwing things out there as I've found even useless suggestions spawn great ideas..

I'm following and if I have anything to offer I'll jump in again.

Yep, there are no connections direct to the battery negative or positive, other than the main cables. And the shunts are both within about 18 inches of the battery. All loads are measured via the shunts.

I'm not familiar with DC-DC charger. How does that limit voltage on the secondary battery?

[Wotname]

Originally Posted by mcon12000

Here's a fun fact and useful if anyone is debating a dirty stud...

The stud doesn't effect the current carrying capacity of the circuit it's the cable terminals and buss bar itself. So yeah that guy would have been better off leaving it alone.

I edited my original post bc it sounded rude. It wasn't my intention sorry...

I dunno if the rated current carrying capacity is predicated on current flowing through the stud or not but I do know that current does flow though the stud and any additional resistance due to a 'dirty' stud does limit the stud current and causes heat.

[sailjumanji]

Originally Posted by MarcoPoloMark

Alaite,
How much distilled water did you add? Could you tell if you over- or under- hydrated (which would weaken the sulfuric acid concentration- or continue starving the electolytic volume- and respectively still diminish performance)? Was there sufficient time for the water to re-hydrate the glass mats and re-energize the sulfuric acid, or did the sulfur leach out with some lead and crystallize into lead sulfites. Did you charge the re-hydrated battery to full using a conventional AGM charger prior to re-testing the Ah capacity? Did the amp/hour capacity improve with added water, or was there another mechanism that was principally responsible for diminished capacity?

Mastervolt AGM's are sealed. There is no way to add water, absent putting a hole in the battery.

[sailjumanji]

Originally Posted by Bycrick

Maybe the nut was tight, but the terminal wasn’t "tight" against the bus bar. If it were, you wouldn’t have gotten enough moisture under ir to corrode the tinning. That’s why they don’t want you to use Nyloc nuts foe electrical connections: you can’t tell whether the torque I’d from the nut or because the joint is tight. A damaged lug, where the end isn’t flat can do this also.

I agree with this. The nut was tight, each had a lock nut, and it took some effort to loosen. That said, I think there was space on that stud due to there being three terminals stacked on it. And they were big wires. You know stacking two terminals and getting them each flat is easy. Three - coming from the same direction - is easier to have some space.

The buss bar is a BEP 300 amp heavy duty buss bar. https://www.bing.com/images/search?v...RST&ajaxhist=0 All of the electrical on the boat is either BEP or Mastervolt - which is the same company. Even the light switches are BEP. No Blue Sea.

[sailjumanji]

Originally Posted by Wotname

I dunno if the rated current carrying capacity is predicated on current flowing through the stud or not but I do know that current does flow though the stud and any additional resistance due to a 'dirty' stud does limit the stud current and causes heat.

Ok, so everyone talks about the corrosion, and it causing resistance, etc. I get that. But the three corroded terminals on that post were solar controller negative, and each of the two outboard motor negative cables. So why was there corrosion there? Why just this post and these three terminals, and none of the adjacent three posts and terminals. Oh, and this bus is located in the bottom of a breaker box, that is located under an upholstered settee in the saloon. Nothing else in there was corroded. Other than humidity, there is no source of moisture. And the saloon is normally closed and behind doors.

Is it just a bad connection? Or is the ground corroding telling of something else?

[sailjumanji]

Originally Posted by MarcoPoloMark

In other words, I'm guessing your loss of capacity is due to severely dehydrated AGMs caused by simultaneous charging from multiple uncoordinated sources. Or maybe just one source is using the wrong absorption charge profile.

An unrecommended proof is to inject a CC or four of distilled water into each damaged sealed battery cell, seal the injection site, charge singly with a proven AGM charger, then capacity test again. It would be easy to inadvertently unbalance the cells by hydrating them unequally, though the cells are likely already unbalanced from the destructive overcharging. Regardless, recovered capacity would definitively prove absorption phase overcharging.

Another proof would be to install new (or mostly healthy) AGMs and fully charge normally with the existing boat system(s), all-the-while listening to the AGMs burp valve(s). These valves are usually designed to release excess gas once the internal pressure is about 2psi higher than the external air pressure. If the AGMs are burping or brapping or farting or raspberrying, you are slowly killing them again.

Simultaneous charging doesnt appear to be happening. As I stated before, when the shore power is switched on, the solar charger immediately drops out. Always does it that way, regardless. When the outboard motors run the voltage up, the same thing happens with solar - drops out. We may be overcharging with the outboard alternators, but it's just a single source.

It would be a good idea to open up these batteries and see what they look like inside, especially regarding the electrolyte. I'm not sure that I'd know what I am looking for, but I can ask Mastervolt. I already have replacement batteries, so not worried about what happens to these. (Although it would be nice not to be spilling battery acid on stuff, on the way to the recycler.)

[Wotname]

Originally Posted by sailjumanji

Ok, so everyone talks about the corrosion, and it causing resistance, etc. I get that. But the three corroded terminals on that post were solar controller negative, and each of the two outboard motor negative cables. So why was there corrosion there? Why just this post and these three terminals, and none of the adjacent three posts and terminals. Oh, and this bus is located in the bottom of a breaker box, that is located under an upholstered settee in the saloon. Nothing else in there was corroded. Other than humidity, there is no source of moisture. And the saloon is normally closed and behind doors.

Is it just a bad connection? Or is the ground corroding telling of something else?

Wish I knew the answers to all these pertinent questions .

As an aside, do you use any low pressure grease like say Dow Corning #4 between the terminals and the buss bar to assist in sealing out moisture and even air?

IME, it significantly reduces long term minor corrosion without adding any appreciable voltage drop across the buss bar / terminal junction.

As a testing regimen these days I have taken to pushing say 10 or 20 amps through terminals and buss bars and measuring the voltage drop across the connections before putting the cable into use. Takes longer but I sleep better knowing I haven't made a error

[mcon12000]

Originally Posted by sailjumanji

Yep, there are no connections direct to the battery negative or positive, other than the main cables. And the shunts are both within about 18 inches of the battery. All loads are measured via the shunts.

I'm not familiar with DC-DC charger. How does that limit voltage on the secondary battery?

They Buck Boost so you can have as an example 14v on the input side of the unit and it delivers 13.1 on the output. You can also have 11v on the input side and get 14v on the output. The output side is programable for any popular battery type and associated charge profile.

What they do for your situation is take the unoptimized output of your alternators and convert it into a controlled charge profile. Since we can't program your alternators with a proper charge profile we'll leave them attached to a battery we can afford to abuse. Then we feed the input of the DC to DC charger with this (start) battery. Now we connect the output of the DC to DC charger to the house battery and program the appropriate charge profile. The really cool part is your outboard can deliver the correct charge profile for almost any battery type including LifePo4 which would normally kill an unregulated alternator. The Victron units will give you up to 30amps and Mastervolt makes them as well I'm just not up on the specs.

In my situation and likely many others the start battery is only asked to start the motor its not used for any loads other than the gauge panel and ignition. It's quickly recharged and never deeply discharged so my alternator is only attached directly to my much larger GEL house bank. My house bank feeds the DC to DC charger which spits out a SLA Profile for my start battery.

The unit automatically turns on when it senses a user selected voltage level from shore, alternator or solar and turns off at a user selected low voltage. So you set the turn on threshold to 13.1v and the turn off voltage at 12.9 and it will do its job only when the alternator is spinning and turn off automatically without draining the start battery.

These devices allow the elimination of A/B/Both switches and unlike ACR's they allow mixing of chemistries.

One of my favorite upgrades!

[MarcoPoloMark]

It is talking, but what is it saying? Maybe something in Galvanic, since the motors are in the water? Maybe something in Static, since the solar panels are in the breeze? Maybe something in Cyclic, since there may be an excessive AC ripple voltage overlaying the DC charging voltage? Maybe something in Mechanic, since there may have been some errant grease or fingerprints or buggers or sweat that impacted that particular connection group. Or back to Galvanic, maybe one of those terminals was a dissimilar metal, an improper alloy from an irreputable source?
It's saying something though.

[MarcoPoloMark]

AGMs are sooooo starved of water, that when drilled, they don't drip. Of course, drilling could cause sparking, could cause exploding, so drilling not recommended.

[mcon12000]

Originally Posted by Wotname

I dunno if the rated current carrying capacity is predicated on current flowing through the stud or not but I do know that current does flow though the stud and any additional resistance due to a 'dirty' stud does limit the stud current and causes heat.

Its not part of the rating its excluded. For example you can purchase both 5/8" and 1/4" attachment holes in a 2/0 Cable Lug. Another example is terminal fuses where the stud is completely isolated or not part of the circuit only the busbar, fuse and cable lug conduct. I know it seems weird but the rating is determined by the current carrying capacity of the materials sandwiched together.

Please don't think I'm saying a rusty old stud is going to be fine that scares the crap out of me. I'm worried it will snap off!

[mitiempo]

Originally Posted by sailjumanji

Yeah, but the MassCombi has a different profile, whereby the bulk voltage is 14.40, and the absorption is 14.25 volts. It's tough to say that the solar controller should be limited to 14.25 to prevent battery damage, whereas the MassCombi shore power charger specifically allows 14.4 volts bulk. In real tests, the 14.4 volts is almost instantaneous, and then the charge drops to absorption voltage. It's not at 14.4 volts for hours, but just a minute or so. It ramps up so quickly, and then drops, you really have to watch it to catch it.

If the battery is at a lower SOC, say 60 % or even 70 %, it doesn't make sense that the charger brings it up to 14.4 immediately. During bulk the charger should take a while, maybe hours on a large bank, to raise the voltage of the battery to absorption level.

[mitiempo]

Here are the specs of the 270 AH super 8D AGM from Mastervolt:

Excellent starter function.
Perfect upgrade for flooded lead acid batteries.
Same initial power surge in an AGM 12/90 Ah as 180 Ah flooded lead-acid battery.
Glass-fibre technology ensures low internal resistance.
Use of thicker plates extends lifespan.
Can be combined with every standard battery terminal.
Also for medium cyclical use.
Two year warranty.

CCA to DIN
750 A
CCA to SAE
1200 A

Notice the line above the warranty information. They - like most 8D batteries made - are basically starter batteries.

Between that and the fact that you ended up with batteries that were sitting (not charging) for a long time their short life in a deep cycling situation isn't a great surprise. This is in addition to the fussiness of AGM batteries that they require being charged fully as often as possible for any kind of lifespan.

I would replace with a true deep cycle battery if possible or it will likely happen again. Mastervolt doesn't make (label) a true deep cycle AGM battery based on their web information.

I have always thought of 8D's as truck starting batteries. Not to mention their weight being hard to deal with.

I just finished removing 4 8D's from a powerboat. 2 were start and 2 were for house loads. We replaced with 8 GC batteries for a larger bank that can be cycled heavily on a regular basis. 460 AH @ 24 volts. I would expect many years of use from the GC batteries.

Sailboats most often have batteries that suffer from PSOC as it is not always easy to fully charge as often as possible. Powerboats, especially those not long term cruising often do better with AGM batteries as they are usually fully charged on arrival at least.

[alaite]

Adding water to the AGM battery was only an experiment because I knew that the battery was already damaged. So I watched some Youtube videos about reviving AGM batteries and I did not expect any miracles. And no miracle happened. The expensive AGMs were gone. We bought new gel batteries of different brand and we hope that they will work better. Many of discussions in this thread talk about decimal of voltages etc. I do not believe that that is relevant. The charger (60A) we are using is intelligent microprocessor controlled type and it is programmed to charge exactly this kind of batteries. Our both battery meters BlueSea and Victron show about the same reasonable values. The batteries just lose their capacity fast.