AGM vs deep cycle

[PaulRainbow]

I'm pretty sure that's true for a heavily used boat or live-aboard, not sure it's true for a typical yacht which gets used for a couple of dozen day sails, a few long weekends and a three-week cruise each year. Or those which seem to be either in the marina or running the engine 80% of the time that people are aboard.
There are a lot of variables.

I agree. It's also not true for a lot of boats that have lots of solar power, where the panels keep up with loads and the batteries never get below 80-90%.

AGM prices keep falling and i'm now regularly fitting AGM starter batteries. I predict that in a very short space of time i'll be routinely fitting AGMs instead of SLAs. There are still installations where T105s make sense though.

 

[JumbleDuck]

I have been doing a lot of research on lithium. From what I can see lithium as a drop in replacement isnt there yet. Victron and Mastervolt can do it but at great expense. The technology is way different to lead acid and far more complicated than you can imagine. If there is a cheap lithium option then from what I have researched, you are very likely wasting your money. There are safety features necessary to operate lithium on a boat. Charging regimes need to be totally different to lead acid.

I think the good Lithium batteries include charging control circuitry in them, so you can connect to a standard set-up without worrying. That would include the 68Ah-for-£600 ones I saw. That's down a fair bit but still not exactly bargain basement.

 

[JumbleDuck]

If these batteries are one-fifth of the weight then perhaps boat stability becomes a factor. I have nearly 200kg of AGM batteries in the lowest part of the bilge, almost in the keel; presumably replacing them with much lighter batteries would necessitate adding some other form of ballast.

In your case that could be an issue. In mine the weight saving would be welcome. In fact, I reckon I could fit 5 x 120Ah lead-acid-equivalent in the space which currently holds 2 x 60Ah actual-lead-acid, and have a significant weight saving. The only (sic) downside would be the £3,000 bill ...

 

[Mistroma]

I agree. It's also not true for a lot of boats that have lots of solar power, where the panels keep up with loads and the batteries never get below 80-90%.

AGM prices keep falling and i'm now regularly fitting AGM starter batteries. I predict that in a very short space of time i'll be routinely fitting AGMs instead of SLAs. There are still installations where T105s make sense though.

Same here. I bought T105s in UK and paid about £1.09/Ah at the time. They made sense as "leisure" batteries weren't that much cheaper, I lived on board 7 months each year and had little or no solar.

Much less clear cut in Greece when price is higher, I have a fair amount of solar and don't really deep cycle very often. I only decided to stick with replacement T105s as they were readily available, price wasn't too eye-watering and they are a perfect fit for my battery box. I could easily have gone for much cheaper batteries.

It is 22:30, I've just watched F1 for 2 hours and batteries are sitting at 98%. I expect they'll be around 90-92% in the morning, not exactly deep cycling. I wouldn't exactly be surprised if a weekend sailor with shore power and solar had a strong preference for cheap batteries.

 

[Momac]

Note it's possible to buy from battery megastore using Ebay or Amazon where the delivery charges are clearly stated.

 

[dom]

I'm pretty sure that's true for a heavily used boat or live-aboard, not sure it's true for a typical yacht which gets used for a couple of dozen day sails, a few long weekends and a three-week cruise each year. Or those which seem to be either in the marina or running the engine 80% of the time that people are aboard.
There are a lot of variables.

True, though I think it also depends a bit on the season. For example, in summer I rarely go below 20% DoD, but during the occasional long mid-winter w/es to Normandy, Brittany, or wherever, I often see the batts repeatedly run deep, especially when not calling at marinas to top-up. In my case, a combination of low solar availability, AP’s working hard, and a slightly dated air heating system — which is less efficient than modern hydronic or Wallas type systems — makes for a fairly heavy demand.

That said, I agree that people should specify/cost to their own requirements and charging capabilities.

 

[lw395]

True, though I think it also depends a bit on the season. For example, in summer I rarely go below 20% DoD, but during the occasional long mid-winter w/es to Normandy, Brittany, or wherever, I often see the batts repeatedly run deep, especially when not calling at marinas to top-up. In my case, a combination of low solar availability, AP’s working hard, and a slightly dated air heating system — which is less efficient than modern hydronic or Wallas type systems — makes for a fairly heavy demand.

That said, I agree that people should specify/cost to their own requirements and charging capabilities.

There also comes a point where spec'ing your batteries around infrequent winter requirements costs more than running the engine more often to charge them. But the most cost effective choice is not always what we want!

 

[Stemar]

There also comes a point where spec'ing your batteries around infrequent winter requirements costs more than running the engine more often to charge them. But the most cost effective choice is not always what we want!

Yet another advantage of solar panels. Even a relatively small solar system will keep your batteries topped up between infrequent uses in winter. My 40W panels mean my 100AH domestic and 80AH starting batteries are almost always fully charged the following week after a winter weekend catching up on jobs, with no mains power.

 

[GTom]

I am also in the process of changing my batteries but have opted for low tech approach.

Current battery set up is 3 x 100 amp wet lead acid car batteries combined house and starter pack. They have been in the boat for nine years and still appear to be fine.

They are charged by alternator and solar panels and require only one charge from a charger at the start of the season after having been left all winter.

The reason for changing is that I have experienced how quickly a battery can die at the end of its life and I don't want to be caught out.

I'm in Holland and it seems that only batteries over 100 amps are now available as wet cell, so I have bought 2 x 190 amp wet cell batteries. They cost the equivalent of £370.

The reason for sticking with wet cell batteries is that, if they have been overcharged, the electrolyte can be topped up. With Sealed and AGM batteries, overcharging results in death of the battery. I also do not need sophisticated ( expensive ) charging systems to ensure longevity which means less electronics to go wrong.

I am a firm believer in the KISS principle!

How much tilt angle do the trojans/hankook/etc SLA-s tolerate? Sailing often involves 15-20° heeling, sometimes much deeper knockdowns...

 

[Graham376]

How much tilt angle do the trojans/hankook/etc SLA-s tolerate? Sailing often involves 15-20° heeling, sometimes much deeper knockdowns...

I've had open lead acid on 4 boats over 26 years, only one broach, and never had a spill.

 

[lw395]

I've had open lead acid on 4 boats over 26 years, only one broach, and never had a spill.

However, ISTR they are frowned on for racing boats?

 

[geem]

However, ISTR they are frowned on for racing boats?

Then it sounds like AGM for on a racing boat for you where none spill is an issue. Certainly never seen any battery acid spills on my boat with open batteries. I think for me we will stay with open wet cell batteries and in a few years time when Lithium becomes cheap and commonplace we will make the jump. We will completely bypass the Whole AGM saga

 

[RichardS]

Open cell batteries are a non-starter for me because of the total inaccessibility of anything other than the first of the three house batteries. I did wonder whether the boat had actually been built around the battery compartment and that we would not be able to replace the 60kg batteries at all but we did manage to do it with some lateral thinking.

I could have used maintenance-free conventional batteries rather than AGMs but open cells would not work.

Richard

 

[JohnGC]

How much tilt angle do the trojans/hankook/etc SLA-s tolerate? Sailing often involves 15-20° heeling, sometimes much deeper knockdowns...

When I asked Trojan this question with regard to T105s they replied, "20 degrees". I think that is a conservative number. Mine have been fitted (monohull) since 2013 and have never spilt a drop. I'm not adverse to a bit of strong wind or bouncy conditions. They are still working well.

This is an interesting read;
https://www.pbase.com/mainecruising/flooded_battery_orientation

John

 

[Mistroma]

When I asked Trojan this question with regard to T105s they replied, "20 degrees". I think that is a conservative number. Mine have been fitted (monohull) since 2013 and have never spilt a drop. I'm not adverse to a bit of strong wind or bouncy conditions. They are still working well.

This is an interesting read;
https://www.pbase.com/mainecruising/flooded_battery_orientation

John

I haven't looked at the article yet but can comment from experience. As soon as my first set of T105s were delivered, they were fully charged, topped up to exactly the correct level and tilt tested.

I would need to look up the results to confirm but seem to remember I slowly tilted them to 45 degrees with the cap off before the electrolyte came close to spilling. I think that I tried sloshing a bit around that angle them around with the caps firmly down. No spillage seen at that time and I've never seen signs of leakage in use even after sailing for hours at a serious angle of heel.

N.B.
I mainly tested the T105s by tilting in line with the plates as that's how I installed them. It would be better to have installed them with the plates lined up fore and aft. However, I couldn't install them in that configuration.

I did try tilting them to 45 degrees in the other direction once and no spillage with the caps on.


EDIT: Just had a quick look at the article and see that it covers orientation. I would have preferred to alter mine but don't worry unduly. Most usage is at anchor when level and total hours sailed very well heeled isn't that high in relation. I also imagine that the electrolyte will slosh around quite a bit and keep the plate moist for a short time.

 

[ANDY_W]

How much tilt angle do the trojans/hankook/etc SLA-s tolerate? Sailing often involves 15-20° heeling, sometimes much deeper knockdowns...

With wet cell lead acid batteries I've yet to suffer from loss of electrolyte up to 30 degrees of heel. However, if I had, all that I would need to do is mop up and top up in order to have a working battery again.

Being an old fogey, I have become concerned about modern electrical systems and the need for evermore electronics to ensure they keep operating in ever decreasing range limits.

Such systems are fine for road transport where the worst consequence is that a vehicle stops at the side of the road or, at the other extreme, air transport which has an intensive preventative maintenance regime.

On a boat, operating in a potentially hostile environment, you need systems which are robust and, above all, easily repairable.

Imagine on a dark and stormy night, with electrical failure, trying to determine if the battery internal electronics or the smart charging system was at fault. If you could find the problem, could you fix it?

I note the point about battery weight when comparing different types but unless you are such such a skilled sailor that a miniscule increase in relative weight would noticeably affect boat performance, I don't think it matters.

 

[Keel]

If any interest, Tayna via ebay are selling with free delivery and 20% off witht the code PLENTIFUL - a useful saving compared to their main website for my new AGM battery.