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AGM vs Traction


Robbo

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Just opening a discussion on AGM batteries.

 

AGM's seem to have a few advantages over Traction batteries, the main ones is that they can charge quicker and if not fully charged regularly don't suffer from sulfation as much (especially the TPPL versions).

 

I'm a off-grid liveaboard and charge the batteries via a inboard generator. Im debating with myself if these batteries at double the cost are worth the extra and long term if the extra cost will be deninisished from the quicker charging. I don't tend to look after the batteries as much as I should either!

 

What are your views?

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Can you quantify the "charges quicker" thing and in fact whether they charge quicker at lower SoCs but take the same time to go from say 90% SoC to 100% SoC, or whether the faster charging is across the board? This is not a rhetorical question, but an important one since for other factors I'd go for traction - cheaper, more robust (e.g. ability to equalise if allowed to sulphate, can tolerate deeper discharge). I suggest that AGMs are only a good idea for rock and roll boats (ie those on the ocean).

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Thin plate and traction are the opposite end of the battery spectrum.

 

Thick plates give long lasting performance, but take and give up power slowly, thin plates do the opposite, and usually fail early because of the increased mechanical stresses on the plates.

 

Pure lead plates are good, because they do not suffer plate or group bar corrosion.

 

When valve regulated sealed lead acid batteries (to give AGM's their proper name) appeared around 1980, the critical power industry adopted them almost overnight, because of the labour costs saved in not having to top up, or manually charge.

 

What followed was that most batteries failed well before their promised 10 year life, typically after 5 or 6, especially where ambient temperatures were elevated. The only VRSLA batteries which lasted 10 years were Rolls (later Hawker Energy), which were thick plate pure lead VRSLA's. Indeed the resultant warranty claims pretty much ended Chloride and Tungstone as battery manufacturer's. Yuasa now provide most VRSLA's to the critical power industry. They are pure lead, with medium thickness plates, but still struggle to last 10 years.

 

So it is horses for courses, tractions are large, heavy and expenaive, but are ideally suited to off grid liveaboard use.

 

Quality AGM's are just as expensive, but don't require much in the way of maintenance and are ideally suited to leisure use, or applications where space is at a premium to the extent it makes maintenance almost impossible.

 

Edited to add the bit about Yuasa.

Edited by cuthound
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The 50-80% charge amps can be up to 40% of the capacity ah, where on Traction batteries the limit tends to be around 25%. As I do this on the generator I could nearly half my daily charge time and have less wear on the generator, etc.

So that's roughly 45 mins vs 72 mins to go from 50 to 80%, a difference of 27 mins. But what about 80-100%, surely that is what takes the vast majority of the time and, I suspect, won't be significantly quicker with AGMs.

 

And I have a suspicion that very fast charging up to 80% actually results in a longer time to go from 80 to 100%

Edited by nicknorman
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IMO (and only that) Battery life is dependent on many things. Battery type is one, but how you care for them and charge them is seriously important. While any lead battery will take a 5C charge when at 5% SOC doing that charge rate at 95% SOC will kill it by gassing and shedding material from the plates.

 

Work out a good charge regime for your batteries using a generator and solar. Solar will do the charge from 90 - 100% SOC gently which is good for the battery and silently which is good for life and the neighbours.

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I can't comment on the faster charging topic as not really experienced to do so. However I can give my personal experience of AGM use and hope that is useful.

 

I am a liveaboard, off grid, running a 12v fridge, lights and pumps. 240v through 2.5kw inverter charger for TV, stereo, DVD player and washing machine. I have 4 x 130 ah AGM batteries that are now in their tenth year, and just beginning to show signs of tiredness. They are maintenance free, a boon for me as access a bit like doing yoga! They are charged via gennie, alternator and solar panels as needed. Charging is mainly solar spring to autumn, then daily evening charging through winter months. For me they are the way to go and I shall replace with more AGMS.

 

I suppose the advice is to weigh up what your use/punishment of batteries is going to be against what you can/want to pay.

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So that's roughly 45 mins vs 72 mins to go from 50 to 80%, a difference of 27 mins. But what about 80-100%, surely that is what takes the vast majority of the time and, I suspect, won't be significantly quicker with AGMs.

 

And I have a suspicion that very fast charging up to 80% actually results in a longer time to go from 80 to 100%

30mins daily although sounds small is quite a lot over time. For what I gather is that tractions is cheaper per ah if you can look after them and charge them to 100% regularly. However when not charging fully regularly the AGM TPPL's will hold better and last longer, whether that is cheaper overall is a calculation nightmare!

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I can't comment on the faster charging topic as not really experienced to do so. However I can give my personal experience of AGM use and hope that is useful.

 

I am a liveaboard, off grid, running a 12v fridge, lights and pumps. 240v through 2.5kw inverter charger for TV, stereo, DVD player and washing machine. I have 4 x 130 ah AGM batteries that are now in their tenth year, and just beginning to show signs of tiredness. They are maintenance free, a boon for me as access a bit like doing yoga! They are charged via gennie, alternator and solar panels as needed. Charging is mainly solar spring to autumn, then daily evening charging through winter months. For me they are the way to go and I shall replace with more AGMS.

 

I suppose the advice is to weigh up what your use/punishment of batteries is going to be against what you can/want to pay.

What make did you go for, and what make would you replace with when the time comes?

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Some time ago I wrote the following which may or may not help and which may contain errors - I've not had it peer reviewed.

 

Battery Types

For inland waterways use we generally use deep-cycle Lead Acid batteries for powering leisure activities. There are 4 main types of this battery technology that you will come across. Here we discuss the pros and cons of each type. Please note that all voltages quoted are 'typical' for the type of battery being described. Battery manufacturers will supply voltage tables specific to their products.

 

 

Open Lead Acid - Leisure

This is similar to the type of battery that's been around in cars for over 100 years but has heavier plates and is therefore more suitable for leisure use. It has a liquid dilute Sulphuric Acid electrolyte. Be careful - many so-called Leisure Batteries are in reality nothing more than re-badged car batteries; they may be cheap but they will not last long. In general, you get what you pay for, and heavier batteries are usually of better quality than lighter ones (because they contain more lead).

 

Advantages:

Can withstand abuse quite well

Can be equalised at quite high voltages to recover capacity lost through sulphation

Better types can be more deeply discharged than cheaper models

Tend to have plates alloyed with Calcium which increases the gassing voltage making them use less water

 

Disadvantages:

Must have the electrolyte levels checked regularly and topped-up when required

Can release explosive hydrogen gas when being charged

Must be well ventilated in order to dissipate hydrogen gas

 

Open Lead Acid - Semi-Traction

These are similar to Open Lead Acid - Leisure batteries but with much thicker plates containing Lead-Antimony alloy. This makes them more robust and more tolerant of high depths of discharge and with a much longer cycle life. They are heavier due to having more lead within the plates. They typically come in 6 volt or 12 volt styles. The 6 volt ones are popular as golf cart batteries and therefore relatively cheap. The most popular makes are Trojan and Rolls. The Trojan T105 6v cell tends to give best value for money at the time of writing.

 

Advantages:

More tolerant of deep discharge

Much better longevity - provided they are charged correctly

 

Disadvantages:

As Open Lead Acid - Leisure but with increased water consumption.

Sizes and connections may be different from Leisure batteries so there may be a need to modify battery boxes and make up new interconnect leads.

Requires higher final charging voltage to ward off sulphation.

 

Sealed Wet Lead Acid

sometimes called Maintenance Free

This is basically the same battery as the Open Lead Acid above but has a larger quantity of electrolyte and is sealed - it has no removable tops to the cells.

 

Advantages:

No acid spillage

Virtually no maintenance required

 

Disadvantages:

Most manufacturers state that they must be charged at lower voltages than Open Lead Acid meaning slower recharging

Must be regularly fully charged to 100% as most manufacturers state that they may only be equalized (desulphated) more gently (at a lower voltage and hence less effectively) than Open Lead Acid

More prone to sulphation than Open Lead Acid because of the charging voltage limitations.

 

Gel or Valve Regulated Lead Acid

sometimes called Sealed

VRSLA (valve regulated sealed lead acid) batteries have no free electrolyte. The oxygen and hydrogen evolved from the plates during charging is recombined to produce water which is absorbed into fibreglass matting. They are also known as 'Recombination' batteries.

 

Others use a gel type electrolyte. Gel batteries tend to be very expensive. See AGMs below.

 

Absorbent Glass Matt

also sometimes called Sealed or Maintenance Free

AGM batteries have their sulphuric acid absorbed by a very fine fiberglass mat, making the battery both spill-proof and maintenance-free. They are also lighter than conventional lead-acid batteries and tend to be very reliable.

 

AGM batteries have a lower internal resistance than conventional batteries and are therefore better able to supply high currents. 
The internal structure of an AGM battery sometimes has the plates wound in a spiral although this has no effect on their operation. 
They will usually offer a relatively long service life even when deep cycled, partly because they are less prone to Sulphation, and also because they require no maintenance and have a very low self-discharge. Their performance has a gradual reduction over time - they don't 'fall off a cliff' as can happen with other types. They should be stored fully-charged as with flooded batteries.

 

Advantages



The main advantages of AGMs are that they can recharge up to five times faster than flooded batteries

They can be deep-cycled down to only 20% SoC.

 

Disadvantages

The main disadvantage of AGMs is their high cost-to-capacity when compared to conventional flooded batteries. This is somewhat offset though by their available capacity being greater due to their ability to be deeply discharged.

Low float voltage which may not be achievable with some charge sources.

 

AGM batteries perform well at low temperatures (good for boats) but do not tolerate heat well (bad for some engine rooms). 

As with other sealed units, AGM batteries should not be overcharged. A charging voltage of 2.4 volts per cell (14.4V for a 12V battery) is fine; however, the float charge should only be around 2.25 volts per cell (13.5 - 13.6V for a 12V battery), which is much less than for a conventional flooded battery. The battery manufacturer will publish specific voltages - the figures above are only a guide.

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Both AGM's and Tractions are equally susceptible to sulphation if not charged fully often enough. It is because of the chemistry.

 

The boat I bought came with Lifeline AGM's, which are 10 years old and still have about 65% of their original capacity left (proven by doing a discharge test to 50% SoC and calculating the capacity).

 

Lifeline AGM's are unusual, in that they can be equalised periodically, however they are NOT cheap.

 

https://www.tayna.co.uk/Lifeline-AGM-Batteries-S1186-1.html

 

When the time comes to replace them, I will consider changing them to Trojan T105's, but suspect that will require some surgery to the battery boxes.

 

If the surgery is too costly, then I will probably get Lifeline again and a mortgage to fund them (6 for the domestic, 1 for the starter and 2 for the bow thruster).

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I can't comment on the faster charging topic as not really experienced to do so. However I can give my personal experience of AGM use and hope that is useful.

 

I am a liveaboard, off grid, running a 12v fridge, lights and pumps. 240v through 2.5kw inverter charger for TV, stereo, DVD player and washing machine. I have 4 x 130 ah AGM batteries that are now in their tenth year, and just beginning to show signs of tiredness. They are maintenance free, a boon for me as access a bit like doing yoga! They are charged via gennie, alternator and solar panels as needed. Charging is mainly solar spring to autumn, then daily evening charging through winter months. For me they are the way to go and I shall replace with more AGMS.

 

I suppose the advice is to weigh up what your use/punishment of batteries is going to be against what you can/want to pay.

 

That's impressive, I doubt my Trojans will do 10 years. Maybe I need to rethink my opinion on this as I have no first hand experience of AGMs and have just assumed that they are not as good as claimed, looks like they are.

 

Do you have a Smartgage or Amp-hour counter? and if so how low do you typically take them in winter before you recharge?

And is it a full sized washing machine with heater, or a little boaty tin tub thingy?

 

Of course the real drawback with AGM's is that you can't take part in the extensive forum debates about equalisation and charging voltages. biggrin.png

 

.....................Dave

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What make did you go for, and what make would you replace with when the time comes?

They were supplied by the boat builder and are Energy AGMs which I think are no longer. I had an interesting chat with the Multicell rep at Crick about AGM a few years ago, so will pick their brains for replacements, so not sure yet. I will have to make sure the new ones are of equivalent quality and not cheapo copies.

 

That's impressive, I doubt my Trojans will do 10 years. Maybe I need to rethink my opinion on this as I have no first hand experience of AGMs and have just assumed that they are not as good as claimed, looks like they are.

 

Do you have a Smartgage or Amp-hour counter? and if so how low do you typically take them in winter before you recharge?

And is it a full sized washing machine with heater, or a little boaty tin tub thingy?

 

Of course the real drawback with AGM's is that you can't take part in the extensive forum debates about equalisation and charging voltages. :D

 

.....................Dave

Full sized washing machine, but run off gennie on heating cycle.

 

The Stecca solar controller gives me a charge percentage reading and I can reference state of charge from voltage reading on Victron, so 12.2v = 50%, which I don't go below.

 

No equalisation discussions but I do keep an eye on charging voltages!

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This my present boat had 6 x AGMs on it when I bought it they were 2 years old. I only used them for a few months before fitting the full tractions from my previous boat my friend john used them for a year or so before they all failed at less than five years old. The full tractions are still going strong at 12 years old, why bother with AGMs when full tractions are £600 for 720 ah battery bank including a watering system

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This my present boat had 6 x AGMs on it when I bought it they were 2 years old. I only used them for a few months before fitting the full tractions from my previous boat my friend john used them for a year or so before they all failed at less than five years old. The full tractions are still going strong at 12 years old, why bother with AGMs when full tractions are £600 for 720 ah battery bank including a watering system

Space contstraints? Where did you get 720Ah of traction battery for only £600? That is cheaper per Ah than the cheapo leisure batteries.

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Space contstraints? Where did you get 720Ah of traction battery for only £600? That is cheaper per Ah than the cheapo leisure batteries.

I have posted this before we have a big commercial battery supplier at Hellerby in Rotherham John bought a bank from them last year and I bought my second bank from them a few years ago that includes watering system, tails, interconnects and bolts.

Everybody thinks batteries are expensive but thats only true if you buy them from boat suppliers.

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IBCS?

Yes I deal with Neil the sales manager he runs the place when the owner isnt there which is most of the time nice guy but hard to get hold of

I bought 4 x t105 for my broads cruiser last year they were from memory £320 they are lookalikes but are better than leisure batteries

Edited by peterboat
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Yes I deal with Neil the sales manager he runs the place when the owner isnt there which is most of the time nice guy but hard to get hold of

I bought 4 x t105 for my broads cruiser last year they were from memory £320 they are lookalikes but are better than leisure batteries

Hi Peter, do they supply AGMS as well, as my previous post said I think I will need replacements in the not too distant future?

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I'd prefer semi traction to AGM unless battery ventilation is a real problem, or a great deal on high quality AGMs comes up.

 

Global Battery Shop will do a reasonably low priced watering kit, or local supplier may be able to help as Peter says.

 

BUT do check your charging equipment can supply the required temperature compensated charge and EQ voltages or else you may end up SOL :(

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Similar to a previous post I can only comment from a personal experience point of view.

we liveaboard off grid and have 3 x 220 amp Victron AGM batteries which are monitored via smartgauge and Victron BMV 600. These are charged via a built in generator and engine alternator when cruising. No solar yet but that's on the cards.

I don't let the charge drop below 50% although there has been the odd occasion where it's dropped lower. The batteries are 9 years old and appear to be performing well.

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37 minutes ago, Cloudinspector said:

Similar to a previous post I can only comment from a personal experience point of view.

we liveaboard off grid and have 3 x 220 amp Victron AGM batteries which are monitored via smartgauge and Victron BMV 600. These are charged via a built in generator and engine alternator when cruising. No solar yet but that's on the cards.

I don't let the charge drop below 50% although there has been the odd occasion where it's dropped lower. The batteries are 9 years old and appear to be performing well.

Forgive me for saying so but 'appear o be performing well' is a bit arbitrary and woolly. Could you quantify that please?

Specifically, how many "AH used" does the BMV600 report when the Smartgauge is reporting 50% SoC? This will be very helpful as it allows readers to get a grip on how well your well-looked-after batteries are really doing after their nine satisfactory years.

Many thanks if you can do this.

Edit to add:

I'm especially curioous as my four month old Trojanoids are goosed now, having been looked after in exactly the same manner you describe, using much the same monitoring equipment. Do you always go down to 50% before your re-charge? How many days is that?

 

 

Edited by Mike the Boilerman
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