AGM or flooded?

[prv]

Ariam's current domestic batteries are a pair of bog-standard Halfords 80Ah "leisure" batteries, at the end of a hard life in the charter trade. On the crossing back from Cherbourg last month they were sagging by the end of the day despite having spent the previous 36 hours gorging on tasty French 240 while we waited for another gale to blow through. It was lucky that the wind died with the sun and we started the engine, otherwise I think the autopilot may have tripped out before we got home. So, they're getting replaced this winter along with most of the core wiring.

I've always leaned towards traditional flooded batteries on the grounds that I don't need anything fancy, just a big bucket of amps, and good-quality lead-acid is the most efficient way of providing a big bucket. I was thinking of two of these, if I can squeeze them into the locker: http://www.trojanbatteryre.com/PDF/datasheets/L16H_TrojanRE_Data_Sheets.pdf

However, the other week someone posted a link to the offshore racing construction and equipment rules, in reference to something else, and while leafing through I noted that they insist on AGM or gel. Presumably for reasons of spill-resistance in a knockdown. Well, I discount gel based on comments by knowledgeable people in the past (nothing sinister, just that they have been superseded by AGM), but this did make me think that perhaps I should reconsider AGM. Not that I'm planning to get knocked down, but perhaps two big pots of liquid acid isn't the smartest thing to carry on board. Though can you get non-leaking caps for the Trojans? Also less of a requirement for venting, perhaps? I have a vent hose installed, but it's not all that convincing, about four or five metres of 1" pipe leading to a skin fitting. The end splits into three small PVC tubes, obviously designed to push onto a vent fitting on each battery. Maybe I could achieve similar on the Trojans, though I don't think they come with a vent.

Anyway, never having really looked at AGM before, I thought I'd solicit some thoughts from the forum.

Requirements:

• Above average quality/longevity, though not paying for top-of-the-range
• The locker is relatively tall and narrow (still haven't got round to measuring actual dimensions) which dictates choice of physical battery sizes. A horizontal row of the ubiquitous T105s doesn't really work. Unless I could stack them - but that doesn't seem wise.
• As many amp-hours as I can fit in the space, within reason (vs size/weight/cost).
• Able to be charged quickly by a short engine run. Another reason I leant towards flooded, as it's OK to boil off some water by charging fast, since you can then put it back. I have a modern 120amp alternator, no fancy regulator as yet though not averse to adding one if it will genuinely make a difference.
• Worth noting that the L16s have a worthwhile cycle life even with some quite deep discharge (see graph in the above data sheet). Comparisons of available amp-hours need to take this into account if the other system can only operate to 40% or 50% DoD.

All battery-related thoughts welcome.

Cheers,

Pete

 

[pvb]

Some thoughts...

Ordinary maintenance-free "sealed" batteries won't leak. If the boat's upside down, I don't think battery leaks would be the top of my priority list.

AGM batteries can accept high charging currents, so might be worth considering. They'll probably accept charge faster than flooded batteries.

You should ignore your existing battery box and build new box(es) to accommodate more batteries. 2 x 80Ah batteries are nowhere near enough capacity for modern boat requirements. Look to installing 300-500Ah.

 

[prv]

Ordinary maintenance-free "sealed" batteries won't leak.

I'm not going to fit pretend maintenance-free, though. These are just conventional lead-acid with the caps glued shut. They still gas if charged fast, but you can't put the water back, so they die.

If the boat's upside down, I don't think battery leaks would be the top of my priority list.

Upside down, sure - but how far do you have to heel before acid is swishing around the lid of a typical battery? Even 45º looks like plenty to achieve that.

You should ignore your existing battery box and build new box(es) to accommodate more batteries.

Only way to build a new box would be in the middle of the cabin sole. Nowt wrong with the existing one (well, I need to move some trunking around to make best use of the space) and it's in a good location, on the centreline and above the keel.

2 x 80Ah batteries are nowhere near enough capacity for modern boat requirements. Look to installing 300-500Ah.

S'what I'm doing, innit?

Pete

 

[pvb]

I'm not going to fit pretend maintenance-free, though. These are just conventional lead-acid with the caps glued shut. They still gas if charged fast, but you can't put the water back, so they die.

They use calcium in the plates to resist gassing, and have a greater reserve of electrolyte than ordinary batteries. I use "sealed" maintenance free batteries and they typically last 8-10 years. Can't see that's bad value.

 

[pvb]

Only way to build a new box would be in the middle of the cabin sole. Nowt wrong with the existing one (well, I need to move some trunking around to make best use of the space) and it's in a good location, on the centreline and above the keel.

The only way? Nowhere else? I added batteries under bunks.

 

[geem]

They use calcium in the plates to resist gassing, and have a greater reserve of electrolyte than ordinary batteries. I use "sealed" maintenance free batteries and they typically last 8-10 years. Can't see that's bad value.

Ditto. My experience exactly. My last boat had cheap caravan shop batteries that were still going strong at 7 years old when i sold the boat. I think the secret is not to over discharge them. the bigger the bank the less you discharge them. I would go for the largest bank of cheap batteries you can fit. I have this set up on my current boat

 

[vyv_cox]

Both of my boats have sealed batteries, which are now more readily available and in some cases cheaper. Neither set is really old enough yet to judge but the Greek ones (Bosch) are three years old now and appear perfect. I was advised by the chandlery before buying the second set in Milford Haven (Numax) that they have had very good results with them.

 

[prv]

The only way? Nowhere else? I added batteries under bunks.

That's where my existing box is. It's reasonably large.

Pete

 

[charles_reed]

They use calcium in the plates to resist gassing, and have a greater reserve of electrolyte than ordinary batteries. I use "sealed" maintenance free batteries and they typically last 8-10 years. Can't see that's bad value.

I'm stuck with the two original battery boxes in my boat and the only batteries to fit are all Ca-hardened sealed units. I can confirm that I get about 7 years out of them, but that's 7/12 liveaboard.
My understanding is that AGM batteries need a high charging current to ensure circulation of electrolyte (though not so much as gel batteries).
Some charger manufacturers recommend their highest current for charging open batteries (I believe on the hypothesis that you can top up the boiled off electrolyte). My experience has been that Ca hardened batteries (as opposed to antimony hardened plates) take longer to charge at similar voltages.
For these reasons and for capital efficiency I try and use conventional open batteries in my single domestic bank - these last between 10-12 years.

Based upon these unstructured findings, I'd always recommend open batteries and, where possible using traction batteries (which all 6v Trojans are). In pure economic terms I doubt if the cost of one set of Trojan 6v batteries would be less than 2 sets of cheap and cheerful aftermarket batteries.

However not everyone builds their own PC and runs it on a Linux distro, some may prefer the Apple version of Linux - only the incognescenti are fobbed off with Microsoft. ;-)

 

[prv]

However not everyone builds their own PC and runs it on a Linux distro, some may prefer the Apple version of Linux

Presumably that's a metaphor for something pre-packaged and easy to use? Ubuntu, maybe?

Pete

 

[Boo2]

However, the other week someone posted a link to the offshore racing construction and equipment rules, in reference to something else, and while leafing through I noted that they insist on AGM or gel. Presumably for reasons of spill-resistance in a knockdown. Well, I discount gel based on comments by knowledgeable people in the past (nothing sinister, just that they have been superseded by AGM), but this did make me think that perhaps I should reconsider AGM.

If you are governed by the offshore racing rules then that will obviously trump any personal preference but I personally was considering the Trojan range for the same reasons as you : they are reasonable value, have a good rep and will fit in my existing battery box with only minor changes to the wiring etc. I don't think inversion is such a huge thing as far as battery leakage goes, just make sure they are properly strapped down is all...

I say go for the Trojans,

Boo2

 

[Stemar]

Mr Sterling has some thoughts on the subject: http://www.sterling-power.com/support-faq-2.htm

I don't know enough to confirm or deny the accuracy of his opinions, but they do seem to make sense.

 

[RAI]

I follow Mr. Sterling's advice and just look for a form factor that maximises Ah in my battery box space (including room to pour in water or to use a hydrometer when needed).

 

[ianj99]

I use a Sterling digital regulator and until it blew up, their 30amp Procharge D mains charger but I would recommend sealed batteries unless your batteries are easily accessible and you don't mind topping them up every week.
I had 2 wet batteries and was forever topping them up, and quite often didn't do this often enough. I swapped one for an Optima Blue Top sealed and the other will be changed for another agm in the spring. There is no limit on charging current for the Optima but they are very pricey.

 

[geem]

Both of my boats have sealed batteries, which are now more readily available and in some cases cheaper. Neither set is really old enough yet to judge but the Greek ones (Bosch) are three years old now and appear perfect. I was advised by the chandlery before buying the second set in Milford Haven (Numax) that they have had very good results with them.

My caravan shop batteries were Numax. Couldn't fault them. They were also sealed. I paid £45 for 85 amp hr 7 years ago. Very good value

 

[charles_reed]

Presumably that's a metaphor for something pre-packaged and easy to use? Ubuntu, maybe?

Pete

Most of the OS - Android, Apple (from X on), Linux are based on Unix. Only Microsoft (since Win 98 in domestic versions) are based on the old Digital Research architecture seen in the various NT versions. None of the MS OS are stable enough to run mission-critical computers. Ubuntu is, perhaps a poor example of a Linux distro, better are Red Hat or Suse.
More a metaphor for something bloated, as rigid as blancmange, overpriced and prone to bullying its customers and competitors.

 

[prv]

Most of the OS - Android, Apple (from X on), Linux are based on Unix.

I was more gently pointing out that you had described Mac OS X as a kind of Linux. I'm sure the people who make Darwin, and fans of the other BSDs, wouldn't appreciate that

My last job was based mostly on Red Hat, with a fair bit of time also spent on Suse, AIX, Solaris, HP-UX, zOS (both the old MVS world and the newer Unix-like USS) - and occasionally Windows, though I mostly tried to let other people handle that as I'm not very familiar with it. There was also iSeries (or "IBM i" as I think it's officially called now) but I didn't really have much to do with that. My current job is exclusively on Linux.

Pete

 

[ghostlymoron]

Don't turn this into a Microsoft v Apple discussion please. If Windows is so much inferior to Apple OS, why do 90% of offices use MS Windows?

 

[prv]

Don't turn this into a Microsoft v Apple discussion please.

Certainly - I've no desire to do that. I've nothing against Windows, simply not familiar with it as I haven't used it to any great extent since 2002.

Just making clear that Charles's information about Unix may have been a little superfluous here

If Windows is so much inferior to Apple OS, why do 90% of offices use MS Windows?

Might I refer you to your previous sentence above?

Now, back to batteries?

Pete

 

[ghostlymoron]

Certainly - I've no desire to do that. I've nothing against Windows, simply not familiar with it as I haven't used it to any great extent since 2002.

Just making clear that Charles's information about Unix may have been a little superfluous here



Might I refer you to your previous sentence above?

Now, back to batteries?

Pete

Yes Pete, I realised shortly after typing that I had fallen into my own bear trap.