Gel/agm batteries

[marcot]

I need to change the 6 years old wet cell batteries (14x6volt) + starter battery.
Agm or gel? I have a mastervolt battery monitor. Engine is volvo d3 110hp.
Boat is Hallberg rassy 48.

I wonder if there is any issue concerning the 2 alternators.

 

[Cappen Boidseye]

I have just bought two domestic battieries, calcium type. I found that they behaved differently on my intelligent Ring battery charger. When investigating why I read that to fully charge them they should ideally be taken to a higher voltage than ordinary batteries, to 'equalise' the cells I think. Hence I am looking at buying a new intelligent charger with a calcium cell setting.
I think to equalise the cells they need to be charged to 15.2 V and held there for a period, don't know if an alternator circuit will do that.
(This is from memory, I will now try to refresh my memory...

 

[nathanlee]

I need to change the 6 years old wet cell batteries (14x6volt) + starter battery.
Agm or gel? I have a mastervolt battery monitor. Engine is volvo d3 110hp.
Boat is Hallberg rassy 48.

I wonder if there is any issue concerning the 2 alternators.

Gel batteries can, apparently, die/explode if charged or discharged too quickly (prolonged starter cranking?). I don't like the e word, so I opted for AGM - which also has better charging characteristics due to it's lower internal resistance, and is more suited to cranking.

I'm no expert, but I did a LOT of reading on the subject before my purchase. I trust not everything I read was incorrect.

 

[Cappen Boidseye]

I have just bought two domestic battieries, calcium type. I found that they behaved differently on my intelligent Ring battery charger. When investigating why I read that to fully charge them they should ideally be taken to a higher voltage than ordinary batteries, to 'equalise' the cells I think. Hence I am looking at buying a new intelligent charger with a calcium cell setting.
I think to equalise the cells they need to be charged to 15.2 V and held there for a period, don't know if an alternator circuit will do that.
(This is from memory, I will now try to refresh my memory...

My memory is refreshed, calcium type batteries have evolved because they gas less in use and are more tolerant of overcharging. Because of the reduced gassing they can stratify during use, the bubbles in a normal battery help to mix the electrolyte which reduces stratification (stronger electrolyte at the top (or bottom!) of the cell). As the bubbling is reduced in a calcium cell stratification is more of a problem. To fully charge a calcium battery the charger should charge the battery up to 15.8 volts, this will get the battery gassing off and reduce any stratification.
I don't think the old fashioned charging circuit on my boat will be able to fully charge the batteries, so I will probably have to take them ashore or to shore power once every couple of months to give them a full conditioning charge to get the best out of them.
Hope that helped (a bit!)

 

[sailinglegend420]

Agm or gel? ...........I wonder if there is any issue concerning the 2 alternators.

Gels are old technology - 1956 - AGMs are so much better in every respect - BUT not all AGMs are the same so buy genuine DEEP CYCLE, not ones designed for standby Telecom or Solar use. Good ones like Lifeline will last a long time and prove more cost-effective in the end, but you may have to upgrade your Alternator/shorepower chargers to take full advantage of their high current/fast charge rates. My Lifeline AGMs have lasted 8 years so far and still going strong.

See Lifeline's 36 page user manual @ http://www.lifelinebatteries.com/manual.pdf

They used to make Gels also and they offer a fair appraisal of both technologies.

 

[prv]

Are AGMs better than good wet batteries in any way except the non-spilling aspect?

A couple of years ago I specced up a new battery system for KS which I ended up not going ahead with; I decided on a big traditional Rolls traction battery but I can no longer remember why I chose that over AGM. Possibly something to do with faster charging?

Pete

 

[David2452]

I need to change the 6 years old wet cell batteries (14x6volt) + starter battery.
Agm or gel? I have a mastervolt battery monitor. Engine is volvo d3 110hp.
Boat is Hallberg rassy 48.

I wonder if there is any issue concerning the 2 alternators.

Gel is generally better for deep cycle, Absorbed Glass Mat is generally better for high amp draw such as starters and big inverters and will take a higher charge, a bit simplistic I know but a good general rule. But its not just about the batteries, they should be matched to the charging regime, or rather the regime should be matched to the batteries.

 

[Plevier]

My memory is refreshed, calcium type batteries have evolved because they gas less in use and are more tolerant of overcharging. Because of the reduced gassing they can stratify during use, the bubbles in a normal battery help to mix the electrolyte which reduces stratification (stronger electrolyte at the top (or bottom!) of the cell). As the bubbling is reduced in a calcium cell stratification is more of a problem. To fully charge a calcium battery the charger should charge the battery up to 15.8 volts, this will get the battery gassing off and reduce any stratification.
I don't think the old fashioned charging circuit on my boat will be able to fully charge the batteries, so I will probably have to take them ashore or to shore power once every couple of months to give them a full conditioning charge to get the best out of them.
Hope that helped (a bit!)

Stratification is really only a problem in batteries of significant height, on standby (float) rather than cycling duty, and which are not subject to any mechanical agitation (such as gently rocking from side to side).
On a boat, none of those 3 conditions is likely to be met.
Have you ever seen a 2,000Ah 2V cell in a telephone exchange? About 1 metre tall and holding many gallons of acid. That's where you get stratification.
Any wet lead calcium I know of is going to be perfectly happy charged at the typical 14.4-14.8V.

 

[Plevier]

Gels are old technology - 1956 - AGMs are so much better in every respect - BUT not all AGMs are the same so buy genuine DEEP CYCLE, not ones designed for standby Telecom or Solar use. Good ones like Lifeline will last a long time and prove more cost-effective in the end, but you may have to upgrade your Alternator/shorepower chargers to take full advantage of their high current/fast charge rates. My Lifeline AGMs have lasted 8 years so far and still going strong.

See Lifeline's 36 page user manual @ http://www.lifelinebatteries.com/manual.pdf

They used to make Gels also and they offer a fair appraisal of both technologies.

Agree most of that BUT their (Lifeline's) comparisons with flooded batteries are based on very old technology and are not very fair. Flooded batteries have also improved a lot.

 

[Plevier]

Are AGMs better than good wet batteries in any way except the non-spilling aspect?

A couple of years ago I specced up a new battery system for KS which I ended up not going ahead with; I decided on a big traditional Rolls traction battery but I can no longer remember why I chose that over AGM. Possibly something to do with faster charging?

Pete

Actually you could probably get quicker charging with AGMs provided you have adequate charging current available.
I would suspect your choice was based more on likely cycle life.

sailinglegend420 speaks convincingly of his excellent experience with Lifeline batteries but that doesn't seem to be common. He looks after them very carefully and in accordance with their rather atypical instructions for equalisation at a high voltage.

I still feel (as a former manufacturer of both types) that wet cells are more appropriate for most people.

I wouldn't use gel for anything.

 

[prv]

I would suspect your choice was based more on likely cycle life.

Oh - do AGMs die earlier than wet batteries?

Might be re-battery-ing a different boat in a year or two, so back to considering the question again. This time for a boat with a 115amp alternator, probably no regular shore power, but perhaps a small amount of solar. Usual sort of loads for a 34 footer (including radar) and wanting to be independent of marinas. Plenty of space in the battery bay this time, unlike the current boat.

I still feel (as a former manufacturer of both types) that wet cells are more appropriate for most people.

Trying to educate myself on the subject, I'd be grateful to know why that is.

I wouldn't use gel for anything.

I have picked up that impression. In the confusing array of choices, it's nice to be able to eliminate a swathe of possibilities

Pete

 

[sailinglegend420]

Oh - do AGMs die earlier than wet batteries?.....

Batteries don't die - they get murdered!

This is why flooded batteries that can be topped up are better for the majority of people who continually abuse their batteries.

Discharging below 50% DoD is the primary killer - so we need a Battery Monitor, or Digital voltmeter, to tells us before we get to 50%. Difficult to know precisely, when we are continually charging with solar or discharging at night with fridge/lights/computer, etc.. 12.2 volts with no charge or discharge is about 50% DoD, but to measure this we need to disconnect batteries for about 8 hours to let them rest before measuring the voltage. Impractical on a regular basis.

Undercharging is the second killer - using an engine or generator only gets to about 80% - it may take up to 24 hours to get to 100%. If not charged to 100% at least once a month will cause sulfation and reduce their life. Equalization periodically will remove some of this sulfation and extend life. This can only be done with Flooded batteries or Lifeline AGMs. Undercharging also happens because regulators drop down to float voltage before the batteries have reached 100%, and so charging to 100% at these much lower voltage will take a very long time.

Overcharging is the next killer - too high a voltage for too long which causes gassing, or charging at the recommended voltage but not reducing that voltage as the temperature rises. Battery temperature sensors on the regulator will do this automatically. Many boats come with batteries installed in the engine compartment - this will kill sealed batteries very quickly. Every 10 Deg C rise in temperature reduces the batteries life by half.

So it's no wonder that many of us buy the cheapest battery we can find and replace them every 2-3 years. If you are a permanent liveaboard or cruising the Oceans that can be very inconvenient. Good batteries can last 10 years or more and will in the end be more cost effective, but we have to look after them.

 

[Piers]

I need to change the 6 years old wet cell batteries (14x6volt) + starter battery.
Agm or gel? I have a mastervolt battery monitor. Engine is volvo d3 110hp.
Boat is Hallberg rassy 48.

I wonder if there is any issue concerning the 2 alternators.

AGM should (IMHO) be the choice, but whatever you change to, ensure your battery charger is designed to charge that type of battery or you can damage the new batteries.

An important point, but one easily overlooked.

 

[oldfatgit]

My understanding it that good quality deep cycle AGMs should last as long, charge easier/faster, be able to be discharged to a greater extent than wet lead-acid batteries and go through a greater number of discharge-charge cycles. However, being maintenance free it is impossible to er... maintain them beyond keeping them charged and keeping the terminal posts clean and so once they fail there is little one can do.

I believe Gel are very practical but more vulnerable to damage from high discharge currents and being excessively discharged; again being sealed they are impossible to maintain. Sealed for life batteries maybe wet lead acid but with more electolyte included so that they don't need topping up. These are practical but again cannot be proactively maintained and, of necessity have a lower capacity for a given volume as some is taken up with the extra electrolyte.

Wet lead acid batteries of equivalent quality need topping up occasionally with distilled/de-ionised water but can be discharged further and more often than the equivalent other types save good quality AGM. Furthermore, if the plates have become sulphated during a period of discharge they can be de-sulphated with a suitable charger by carefully following the relevant rather brutal procedure.

On balance, when I replace my sealed for life gel leisure batteries, I will either buy lead acid deep cycle ones or, more likely, deep cycle AGM. I prefer the latter because Achates spends hours at 20 to 30 degrees of heel when going to windward and what ever the reality, psychologically I'd prefer a sealed battery bank. I will always keep a leisure battery for engine start as it can handle the loads required by my engine which might challenge/damage deep cycle.

Before I buy I will probably visit a couple of suppliers such as http://www.barden-uk.com/ and discuss my power requirements and charging capabilities in detail before making my choice. On another note I am restoring a narrow boat at the moment and will feed the very powerful charger inverter with a large bank of wet lead acid deep cycle batteries, but narrow boats do not experience rough seas or large degrees of heel.

 

[Piers]

AGM should (IMHO) be the choice, but whatever you change to, ensure your battery charger is designed to charge that type of battery or you can damage the new batteries.

An important point, but one easily overlooked.

I should have added that many chargers have internal switches for choosing the type of battery to be charged. If yours doesn't, you may have to upgrade the charger.

 

[Plevier]

Oh - do AGMs die earlier than wet batteries?

Might be re-battery-ing a different boat in a year or two, so back to considering the question again. This time for a boat with a 115amp alternator, probably no regular shore power, but perhaps a small amount of solar. Usual sort of loads for a 34 footer (including radar) and wanting to be independent of marinas. Plenty of space in the battery bay this time, unlike the current boat.

Wets make more sense for most people because of price and abuse tolerance, in a nutshell.
See sailinglegend's excellent post no 12, he's said it all really!
If you won't have regular shore power, consider the consequences.

You can give other AGMs equalising charges with good effect, but Lifeline are the only people brave enough to put it in the manual for users to do it at their own discretion! Lifeline also call for a higher voltage than we (or any other manufacturer that I'm aware of) did.

Our AGMs were genuinely one of the top two brands and virtually identical to Lifeline in every published respect - plate thickness, grid alloy, separator material (except ours weren't enveloped but I suspect that's really for production convenience), acid saturation etc. and were rated for 10 years life but I would not have claimed the cycle life that Lifeline do.
Lots of people have moaned at getting short life from Lifelines but sailinglegend and some others report excellent results. The key has to be meticulous care of them.
They are only maintenance free in the sense of no topping up; they are not fit and forget.

 

[Plevier]

My understanding it that good quality deep cycle AGMs should be able to be discharged to a greater extent than wet lead-acid batteries and go through a greater number of discharge-charge cycles.

I believe Gel are very practical but more vulnerable to damage from high discharge currents and being excessively discharged; again being sealed they are impossible to maintain.

I will always keep a leisure battery for engine start as it can handle the loads required by my engine which might challenge/damage deep cycle.

(Para nos as edited post above)

Re para 1 - I don't agree, at least not both statements at the same time. Even Lifeline say you shouldn't discharge below 50% SOC for a decent life.

Re para 2 - gels will not normally be damaged by high rate discharge, but will perform poorly on such duty. The big damage danger with gels is trying to recharge quickly, they definitely do not like it up 'em!

Re para 3 - AGMs are brilliant for engine start because it's high current shallow cycle. Don't use a deep cycle Lifeline for that job though - SBS (aka Red Flash), Odyssey, Optima or similar. An ordinary wet will do the job perfectly well - use a starter battery not a leisure - but it seems a shame if your service battery is AGM.

 

[Plevier]

I should have added that many chargers have internal switches for choosing the type of battery to be charged. If yours doesn't, you may have to upgrade the charger.

Be particularly careful if considering Lifeline batteries - very few chargers let you go to the very high equalising voltage that they specify. See the manual from sailinglegend's link.

 

[oldfatgit]

(Para nos as edited post above)

Re para 1 - I don't agree, at least not both statements at the same time. Even Lifeline say you shouldn't discharge below 50% SOC for a decent life.

Re para 2 - gels will not normally be damaged by high rate discharge, but will perform poorly on such duty. The big damage danger with gels is trying to recharge quickly, they definitely do not like it up 'em!

Re para 3 - AGMs are brilliant for engine start because it's high current shallow cycle. Don't use a deep cycle Lifeline for that job though - SBS (aka Red Flash), Odyssey, Optima or similar. An ordinary wet will do the job perfectly well - use a starter battery not a leisure - but it seems a shame if your service battery is AGM.

Thank you. Para 1 - will do more research, you may be right and the propaganda I have read may be wrong. Para 2 - Thanks for the correction, yep agree totally and will be more careful before hitting "Submit Reply" because, well, I knew that all along but typed discharge when thinking charge. Para 3 - ah ha. Does that mean that there are no AGM which are deep cycle?

 

[Plevier]

Para 3 - ah ha. Does that mean that there are no AGM which are deep cycle?

AGMs, just as wets, need to be designed for the application. There are many cheap ones for which the main market is alarms and emergency lighting. There are a few which are good for engine starting. There are a few which are good for long life standby - telephone, UPS etc. There are very few that will cycle.
Indications are that the best AGMs for a good cycle life are Lifelines. See sailinglegend's remarks.
Most wets won't give good life if you regularly go below 50% either.
The ultimate deep cycle batteries have what are called tubular positive plates. They are big, heavy, expensive and mainly used in fork lift trucks and in critical solar systems, sometimes in gel form for the latter.
I'd still tend to back a high quality flat plate wet such as Trojan or Rolls against any AGM for cycle life but that's based on general background experience.
I'm old fashioned and prejudiced and sailinglegend thinks I'm wrong!