AGM batteries, PSOC and sulphation

[ranger58sb]

I'm expecting to replace our 10 year old (initially) 300-Ah bank of 3x Odyssey PC2150s (G31s) probably next year. I can instead fit 3x Lifeline GPL-31XTs, for an initial capacity increase to 375-Ah.

Doing that would be more expensive than just buying new batteries, because our existing charger for that bank won't let me set voltages properly for Lifelines... whereas the single Flooded/AGM setting on our older charger is well suited to the Odysseys. Just yesterday I began a process to install a new charger...

I hadn't before seen reports that Lifelines may sulfate more than Odysseys....

OTOH, we are almost always able to recharge to 100% after most cycles.

Hmmmm...

-Chris

[Glasshopper]

Could those who've observed lower AGM lifespan being a peculiarity of cruising use, could you please confirm if you'd modified your engine alternator charging circuits such that the AGMs are not subjected to 14.4 (ish) volts FULL TIME whenever the engine is running?
My AGMs are labelled as requiring 13.6-13.8V in standby duty and 14.5-14.8V in cyclic duty -i.e. when becalmed and motoring for 24 hours, we're supposed to reduce the charging voltage to 13.6-13.8V after the capacity is restored (a few hours max, if your alternator is correcly sized) otherwise we are electrolizing thwe water content into hydrogen & oxygen, thereby drying out the electrolyte.
Are you certain that sulfation is the faulure mode?
-Regards, Rob Taylor.

[john61ct]

Of course there are multiple factors involved in early end of life, including failing to correctly drop to Float.

PSOC just happens to be the one being discussed here.

Many cruisers do not use their motor so many hours at a time,

some don't even feed House bank from alternators,

and it can take more than a few hours to even get to Absorb stage anyway.

But yes, whenever alternators are discussed here as a charge source, converting to a three-stage VR like Balmar MC-614 is always recommended.

But the fact remains, even where plentiful energy inputs are readily available, chronic PSOC is **very** common, simply from charge sources not being adjusted to hold Absorb time long enough.

Absorb holding too long, and thus overcharging is indeed a problem, but much less frequently.

Some owners will suffer from both,

all depends on the context.

[Exile]

Originally Posted by Glasshopper

Could those who've observed lower AGM lifespan being a peculiarity of cruising use, could you please confirm if you'd modified your engine alternator charging circuits such that the AGMs are not subjected to 14.4 (ish) volts FULL TIME whenever the engine is running?
My AGMs are labelled as requiring 13.6-13.8V in standby duty and 14.5-14.8V in cyclic duty -i.e. when becalmed and motoring for 24 hours, we're supposed to reduce the charging voltage to 13.6-13.8V after the capacity is restored (a few hours max, if your alternator is correcly sized) otherwise we are electrolizing thwe water content into hydrogen & oxygen, thereby drying out the electrolyte.
Are you certain that sulfation is the faulure mode?
-Regards, Rob Taylor.

It's a good question and one that's been debated at length. The consensus seems to be that it's the better practice to have external 3-stage regulators on your alternators, maybe especially so with deep cycle AGM house banks. But this installation comes at a pretty high cost, so others decide the potential harm is offset by the fact that internally regulated alternators often don't run as high as ~14.4V, and when you're motoring you generally have a draw on your house bank, whether it be lights, radios, instruments, etc.

Purely anecdotal, but in my case I have had some lengthy motoring runs (24 hrs.-plus) when there's been no wind and I wanted to get somewhere, and can't say whether this has shortened my battery life or not. My last set of Lifeline's lasted 8 years, but they also spent a lot of time plugged into shore power and were conditioned/equalized periodically. I guess it's another one of these vagaries about battery life that's hard to quantify.

Edit: I've had the same, internally regulated "dumb" alternators on my boat since purchasing it 12 years ago.

[roland stockham]

Originally Posted by Glasshopper

Could those who've observed lower AGM lifespan being a peculiarity of cruising use, could you please confirm if you'd modified your engine alternator charging circuits such that the AGMs are not subjected to 14.4 (ish) volts FULL TIME whenever the engine is running?
My AGMs are labelled as requiring 13.6-13.8V in standby duty and 14.5-14.8V in cyclic duty -i.e. when becalmed and motoring for 24 hours, we're supposed to reduce the charging voltage to 13.6-13.8V after the capacity is restored (a few hours max, if your alternator is correcly sized) otherwise we are electrolizing thwe water content into hydrogen & oxygen, thereby drying out the electrolyte.
Are you certain that sulfation is the faulure mode?
-Regards, Rob Taylor.

This suggests a straight voltage regulator controlling the alternator output to a single fixed value. Such a system will be very ineffective as a charging system an probably give short battery life. For any systen whether it uses LA or Lithium batteries you must have a 3 step regulator that converts the alternator into a smart battery charger if you want to use engine charging. Any fixed voltage system (such as on a commercial motor boat) has a fixed voltage at float level but batteries are not cycled.

[john61ct]

Or alternatively put a DCDC charger in front of the bank input

and then any old charge source including stock alt output will do.

[Exile]

Originally Posted by john61ct

Or alternatively put a DCDC charger in front of the bank input

and then any old charge source including stock alt output will do.

Which battery-to-battery charger did you have in mind that can use an alternator as a charge source?

[john61ct]

Every one on the market, that is their primary use.

Some of the newer / cheaper ones also bundle a small solar unit, IMO better to purchase a dedicated one.

Some require a manual or IGN switch or VSR/ACR, others include the latter functionality.

Some the output setpoint is user-custom adjustable, perhaps requiring a remote to do so. Others just have a selection of canned profiles to choose from.

They vary in amps output, on some that can be adjusted as well, and some can stack multiple units if you need more.

All are successful at preventing alt overload with LFP chemistry if the stock VR does not handle overcurrent / overtemp protection well.

In order of preference, but of course features required depends on the use case

Sterling
Victron
Mastervolt
Optimate
Kisae
CTEK
Renogy
Votronic
Enerdrive
Intervolt
Projecta
Redarc
Powerstream
Ironman

[Pete7]

Originally Posted by john61ct

But yes, whenever alternators are discussed here as a charge source, converting to a three-stage VR like Balmar MC-614 is always recommended.

Oh, by whom? the purveyors of Balmar alternators perhaps? Not cheap though are they?

Originally Posted by john61ct

Or alternatively put a DCDC charger in front of the bank input

That might be a better alternative, for a small to medium sized boat. Or of course the even cheaper AR could be used, £140 from the manufacturer:

https://sterling-power.com/collectio...-bw-waterproof

Which would you fit if there were budget constraints which most cruisers have?

Originally Posted by john61ct

But the fact remains, even where plentiful energy inputs are readily available, chronic PSOC is **very** common, simply from charge sources not being adjusted to hold Absorb time long enough. Absorb holding too long, and thus overcharging is indeed a problem, but much less frequently. Some owners will suffer from both, all depends on the context.

Perhaps all owners suffer from one or both eventually. Guess we just have to accept that eventually batteries die.

Pete

[john61ct]

Originally Posted by Pete7

Which would you fit if there were budget constraints which most cruisers have?

I agree that a quality alt refit can be overly expensive. I personally prefer the B2B approach.

As for the AR units, they're in between, solve that one issue but not as flexible as the B2B,, for my personal use cases.

But every boat and owner are different, I think getting it right to fit the use case is worth spending the extra money.

For a lead bank that cost under a couple grand, owner without much capital, maybe putting up with reduced lifetime from suboptimal care is the way to go.

[sailorboy1]

So I skimmed through the thread.

Was there any proof of the belief that agm battery suffer more from partial recharging? I’m talking proof based on testing and science and not rumor?

[john61ct]

No studies have specifically addressed the question, that anyone's found anyway.

To me, the fact that

FLA lasts much longer on average than AGM, combined with the fact that

PSOC conditions are nearly universal for those away from shore power, likely by far the leading cause of shortened life

makes it very likely.

And given the fact that (in NA markets) quality AGM costs a lot more than FLA, it seems obvious to me that's the way to go there

unless one of the advantages of AGM is compelling for a given owner / use case.

Down under or in Europe, quality FLA is not as common / inexpensive, so the scales may tip in the other direction.

[sailorboy1]

That’s all code for

No, we just have an unproven group think that has been repeated over and over

It seems a simple and cheap thing to do a test on. Maybe we could get Practical Sailor to do it.

[a64pilot]

Originally Posted by sailorboy1

So I skimmed through the thread.

Was there any proof of the belief that agm battery suffer more from partial recharging? I’m talking proof based on testing and science and not rumor?

Not that I’m aware of, but I’d bet lunch it’s been tested, surely sulphation rates of at least Gel, flooded and AGM has been tested?
I don’t believe it’s common for batteries to “wear” out, wear meaning the lead becomes mud so much that there is not enough lead left.

Some will short put from the mud build up, but most I think just lose so much capacity from sulphation that they are replaced.
I believe that very often these excessive lives we hear of, the batteries actually were technically dead for years but just were continued to be used.

[sailorboy1]

Btw I’m using fla golf cart batteries and have no skin in this battle. But I like facts that are based on testing and science over the rumor of “everyone knows that ......”