I don't understand batteries

[ranger58sb]

Originally Posted by goboatingnow

AGMs are not a good fit for boats and Gel is even worse , AGMs are regularly damaged by boat charging practices ...

I think I'd offer an edit of that to something like:

AGMs might not be a good for some boats, especially cruising boats which seldom visit a dock for shore power, don't have solar power, and/or don't want to use a generator.

I don't know all that to be true; it's just from reading, often here...

But I can also say from first-hand experience that we have routinely gotten 11-12 seasons from good AGMs, probably because we are easily able to recharge as often as necessary, using either shore power or the generator. And some years, we put a couple thousand miles on the boat...

Also, there are a bazillion boats of various configurations out there -- my guess is many more than "cruising boats" -- that do NOT stay away from the dock for overly long periods (relative to battery recharging), and/or that DO run a generator whenever useful, and/or maybe even have solar... and who are well served by AGMs if they suit the use case.

IOW, a blanket "they're unsuitable" just seems too dogmatic...

-Chris

[goboatingnow]

The reason I make the general comment is that undercharging is chronic on boats , and AGMs degrade faster the wet acid if subject to a lot of partial charge discharge cycles , they were designed for long periods fully charged.

Furthermore AGMs requires carefully set charging parameters temperature sensing etc. the use of older cruder equipment can cause damage. I’ve seen numerous expensive AGMs under deliver and leave the owners bewildered.

The fact is of you have regular shore power or high performances solar you need less sophisticated batteries.

Really dollar for dollar either very long life Li or cheap and cheerful replaceable sealed wet acid is probably the best. High end AGMs are now as dear as Li and Li is a far more robust technology especially LFP.

[rslifkin]

Yes, AGMs are more sulfation sensitive. So they don't work for all boats and usage patterns. But they do work well within their limitations.

I'm curious what the concern around gel batteries is. They generally hold up well and they're at least as PSOC tolerant as wet cells if not more.

[goboatingnow]

Originally Posted by rslifkin

Yes, AGMs are more sulfation sensitive. So they don't work for all boats and usage patterns. But they do work well within their limitations.

I'm curious what the concern around gel batteries is. They generally hold up well and they're at least as PSOC tolerant as wet cells if not more.

AGMs and GEL largely have beneficial characteristics that cannot be exploited on typical boats , whilst their disadvantages are,

AGMs were designed for high charge acceptance , typically well above what a typical boat would generate and high fast and deep discharges are not a common feature either , physical orientation is not an exploitable benefit in the main

GELs are designed like AGMs for long term storage at 100%SOC not a situation typical on a boat. They are very sensitive to excessive overcharging and require custom gel specific charge profiles. Again they have benefits that are not exploitable.

When you boil it all down , VRLA wet acid , offers good value for money , is tolerant of poor charging regimes ( to a point of course ) and is compatible with typical boat usage patterns. It’s certainly the predominant type around me here.

If you want better skip to LFP, even mediocre quality LFP is better then good AGM at comparable pricing

[Rumrace]

It’s Newfie Love perfectly normal. They were on wood and a complete stranger probably tended to them. It ain’t magic it’s newfoundland.

[ranger58sb]

Originally Posted by goboatingnow

AGMs and GEL largely have beneficial characteristics that cannot be exploited on typical boats , whilst their disadvantages are,

AGMs were designed for high charge acceptance , typically well above what a typical boat would generate and high fast and deep discharges are not a common feature either , physical orientation is not an exploitable benefit in the main

I suspect your idea of what a "typical" boat is... is very limited. I suspect there are many, many more boats NOT like yours than there are boats that seem to be "typical" in your view.

Thinks of all the bazillions of boats in dry stacks, all the trailer boats, all the day sailors (I'm surrounded by a couple hundred of those just now), all the boats originally envisioned by the builders as marina-hoppers.... where periods of time at anchor are generally infrequent and/or short...

And I suspect many boats can take advantage of high charge acceptance, etc.

No argument that wet batteries can be good value. I'm only saying AGM has it's place, and the option is not "inappropriate by definition."

-Chris

[PaulCrawhorn]

Only a CC load capacity test will accurately measure true State of Health.

Yes, that is unusual performance after long abuse, obviously isolated well from parasitic loads, and somehow very slow self-discharge rate.

I would replace regardless if heading out into primitive cruising grounds.

[Tetepare]

Mike,

A couple anecdotal experiences:

Our previous boat had two lead acid G27 deep cycles. Used six months, the charged and disconnected, but left on boat, for six months. They lasted 12 and 11 years, respectively.

Our current boat came with one G27 AGM. It is not sealed; some sources say it's not really AGM, and/or not really deep cycle (despite what the manufacturer says). I added an identical battery.

The old G27 puts out 12.5+ volts. A hydrometer test this spring indicated it was good in all cells except one, which was OK. However, it can't run a light load (fridge, instruments) for four hours and then start the motor. So despite what it appears, the battery is toast.

[Mike OReilly]

Thanks folks. Like I said, I haven't tried a load tester, mainly because I don't have easy access to one. But I have run both banks (house and starter) through their paces. The house in particular has gone through multiple cycles running house loads over the full 24hr cycle. Fridge, lights, pumps, fans, instruments (although not auto helm).

Worst overnight drop was 12.5v. Solar/wind brought it back up before 11am. This is consistent with the way they've always performed. So while I have no doubt they've degraded over their long hibernation, the decline does not appear to be large.

I remain surprised by this, but it does appear to be true.

[kayakerChuck]

I don't think anybody understands batteries.

I think they are just storage containers for high pressure magic smoke.

[Island Time O25]

This spring had 2 deep cycle 27s get below 12v after not charging them during last few months of winter storage.

But the punch line is that one was purchased in 2010 at HD, the other in 2014 at Walmart. Each for under $100, more like $80-90. Go figure.

[rslifkin]

Originally Posted by Tetepare

Mike,

A couple anecdotal experiences:

Our previous boat had two lead acid G27 deep cycles. Used six months, the charged and disconnected, but left on boat, for six months. They lasted 12 and 11 years, respectively.

Our current boat came with one G27 AGM. It is not sealed; some sources say it's not really AGM, and/or not really deep cycle (despite what the manufacturer says). I added an identical battery.

The old G27 puts out 12.5+ volts. A hydrometer test this spring indicated it was good in all cells except one, which was OK. However, it can't run a light load (fridge, instruments) for four hours and then start the motor. So despite what it appears, the battery is toast.

If it's got openable caps and you can get electrolyte out of it to use a hydrometer then it's definitely not an AGM. Just a plain old wet cell.

[Mike OReilly]

Originally Posted by kayakerChuck

I don't think anybody understands batteries.

I think they are just storage containers for high pressure magic smoke.

I'm beginning to suspect you may be close to the truth.

[StuM]

Originally Posted by Tetepare

Our current boat came with one G27 AGM. It is not sealed; some sources say it's not really AGM, and/or not really deep cycle (despite what the manufacturer says).

The old G27 puts out 12.5+ volts. A hydrometer test this spring indicated it was good in all cells except one, which was OK

If it's not sealed and you can suck up battery acid wih a hygrometer, it is DEFINITELY not AGM


"An AGM (absorbed glass mat) battery contains a special glass mat separator that wicks the electrolyte solution between the battery plates. This material’s design enables the fiberglass to be saturated with electrolyte – and to store the electrolyte in a “dry” or suspended state rather than in free liquid form"

[goboatingnow]

Originally Posted by ranger58sb

I suspect your idea of what a "typical" boat is... is very limited. I suspect there are many, many more boats NOT like yours than there are boats that seem to be "typical" in your view.

Thinks of all the bazillions of boats in dry stacks, all the trailer boats, all the day sailors (I'm surrounded by a couple hundred of those just now), all the boats originally envisioned by the builders as marina-hoppers.... where periods of time at anchor are generally infrequent and/or short...

And I suspect many boats can take advantage of high charge acceptance, etc.

No argument that wet batteries can be good value. I'm only saying AGM has it's place, and the option is not "inappropriate by definition."

-Chris

I stand by my opinion based on years of sorting out boat electrics, and my professional expertise, the categories of boats you mention gain nothing by deploying AGMs , if you have access to regular 100% recharging , you have little need for batteries at all.

AGMs have several advantages , nearly all are not exploitable by boats. I often see people buying AGMs conflating them with getting a superior wet cell, when in fact if they want good quality cells they should simply buy good quality wet cells. To many times I’ve seen retailers oversell AGMS to largely unsuspecting and unaware boaters.