Equalising AGM batteries

Plevier said:
I think damaging sulphation is more due to being left discharged or undercharged than being over discharged (i.e. very deeply discharged) per se.
The discharged state of both the positive and negative plates is lead sulphate PbSO4, so in a sense sulphation occurs in every cycle, and any recharge process is desulphation.....
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"I think......," and "so in a sense......" are not really getting over your message. EVERY discharge cycle causes sulfation - as you say that is the conversion of parts of the Lead plates (and the H2SO4 electrolyte) into Lead Sulfate and water, PbSO4 and H2O. Charging reverses that process and the SO4 recombines with the H20 that has diluted the electrolyte which is why the SG values rise when charged. There are lots of + and - ions and H2 an O flying around as well!

So sulfation is ONLY a problem if the battery is not fully re-charged because the Lead Sulfate crystals harden, and the longer parts of the plates are not fully charged the harder these Lead Sulfate crystals become, which makes it harder to remove them. If the batteries haven't been fully charged every 2 or 3 weeks then a high Equalisation voltage once a month should remove the hardened Sulfation.

I Equalise my Lifeline AGMs about twice a year, but now ONLY because they are showing signs of a lack of capacity after 10 years as a fulltime liveaboard. I wouldn't do it every month as Morgans Cloud recommend!

When I EQ them they only start to gas VERY slightly after about 5 hours, nothing like an FLA that bubbles vigorously. Nearly 100% of the gas generated is recombined into water and kept inside by the valve regulator cap that keeps the internal pressure at about 6 PSI.

I believe Red River AGMs also recommend equalisation. I think Nigel Calder also uses EQ voltages on his Odyssey TPPL batteries which seem to be giving him some capacity problems. If you have AGMs that have lost capacity then maybe there is little to lose if you EQ them. My Lifelines certainly come back up and maintain there voltage longer between recharges.


MikeBz's comment about US and UK different charging voltage I think refers to GELs NOT AGMs. They are very different types of battery and shouldn't be confused.
 
MikeBz said:
Apologies if I've got that wrong. I did a lot of reading up on various 'smart' battery chargers and AGM battery products and formed that view bolstered by the fact that my A2B (and I thought some other chargers I looked at) has different settings for 'US' and 'Euro' spec AGM batteries. Maybe it's a marketing gimmick, or is a misrepresentation of differences between spiral wound and non-spiral wound battery requirements? There is a lot of variation on manufacturer advice hence the need for caution before anyone jumps in and has a go at desulphating their batteries.

Optima claim that "Sealed AGM batteries do not sulfate or degrade like flooded batteries do, since they are not vented to the atmosphere" (http://www.optimabatteries.com/en-us/technology/agm-batteries). It seems like a strange claim to make (other types of sealed battery are available which do sulphate) and contradicts the advice that Morganscloud has had from Lifeline.
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Spiral wound is different again, originated by Gates (Cyclon cells) but Optima seem to have become more prominent at least in the end user market, I think Gates are probably still bigger in OEM industrial stuff.
Cyclons are made from spirally wound pure lead foil, with higher specific gravity acid and much higher operating pressures. They were the pioneering recombination cells from which current AGM technology has been developed. They are now out of patent and I think Optima are very similar to them.
They both seem to have very long lives albeit at very high initial cost - but they do sulphate and degrade in other ways eventually.
Cyclon and Optima are not representative of all US AGMs, they are oddballs! There are other US AGMs which are flat plate pure lead and others which are flat plate lead calcium (plus other alloying elements such as tin and silver), just as there are in Europe and from Far East producers too.
The US was actually slow in developing flat plate AGMs, lagging behind UK and Japan.

Charger manufacturers do love to group different batteries together, sometimes rather inappropriately. "Euro spec AGM" and "US spec AGM" are definitely not valid groupings. If in doubt, take the battery manufacturer's recommendation in preference to the charger manufacturer's!
 
RobbieW said:
I was guilty of believing that 3 conditions - sulphation, cell inequality & stratification - had but one remedy called equalisation.
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Well I can't really argue with that, taking equalisation to mean charging at a higher than normal voltage! However of the 3, sulphation is the hard one to deal with.
 
sailinglegend420 said:
"I think......," and "so in a sense......" are not really getting over your message. EVERY discharge cycle causes sulfation - as you say that is the conversion of parts of the Lead plates (and the H2SO4 electrolyte) into Lead Sulfate and water, PbSO4 and H2O. Charging reverses that process and the SO4 recombines with the H20 that has diluted the electrolyte which is why the SG values rise when charged. There are lots of + and - ions and H2 an O flying around as well!

So sulfation is ONLY a problem if the battery is not fully re-charged because the Lead Sulfate crystals harden, and the longer parts of the plates are not fully charged the harder these Lead Sulfate crystals become, which makes it harder to remove them. If the batteries haven't been fully charged every 2 or 3 weeks then a high Equalisation voltage once a month should remove the hardened Sulfation.

I Equalise my Lifeline AGMs about twice a year, but now ONLY because they are showing signs of a lack of capacity after 10 years as a fulltime liveaboard. I wouldn't do it every month as Morgans Cloud recommend!

When I EQ them they only start to gas VERY slightly after about 5 hours, nothing like an FLA that bubbles vigorously. Nearly 100% of the gas generated is recombined into water and kept inside by the valve regulator cap that keeps the internal pressure at about 6 PSI.

I believe Red River AGMs also recommend equalisation. I think Nigel Calder also uses EQ voltages on his Odyssey TPPL batteries which seem to be giving him some capacity problems. If you have AGMs that have lost capacity then maybe there is little to lose if you EQ them. My Lifelines certainly come back up and maintain there voltage longer between recharges.


MikeBz's comment about US and UK different charging voltage I think refers to GELs NOT AGMs. They are very different types of battery and shouldn't be confused.
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Can't argue with any of that, I would just adjust your 2nd para to say "... may help to remove some of the hardened sulphation." (Sorry I can't put an "f" in it! :))
Never heard of Red River AGMs, no luck on Google. I found "Full River" - never heard of them before but they offer some large capacities.
I've always said that Odyssey were inappropriate for Calder's electric propulsion project, very strange choice.
You could be right about gels, that didn't occur to me. Gels are not AGMs but are often confused. I regard gels as completely unsuitable for boat use.
 
Plevier said:
I think damaging sulphation is more due to being left discharged or undercharged than being over discharged (i.e. very deeply discharged) per se.
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The original was based on discharging to flat and recharging to 50% recharge level. It seams odd but this is common, people would discharge the battery in the marina at night, then motor for half an hour till open water sail for the day, motor back up to the marina, Over a period of time of using more than charging, the average capacity got lower and lower, result heavy discharge, limited recharge and sulphation.

Brian
 
sailinglegend420 said:
I Equalise my Lifeline AGMs about twice a year, but now ONLY because they are showing signs of a lack of capacity after 10 years as a fulltime liveaboard. I wouldn't do it every month as Morgans Cloud recommend!.
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It's worth noting that the once a month equalising regime came from lifeline as the batteries are worked so hard...


--
Justin Godber at Lifeline, who provided us with new batteries, defined what expected battery life should be, depending on charge regime, assuming daily discharge to 50% and full time voyaging.

Fully recharged at least once a week and equalized once a month. Estimated life: 4-6 Years.

--
What works on one boat might not be suitable on another.
 
halcyon said:
The original was based on discharging to flat and recharging to 50% recharge level. It seams odd but this is common, people would discharge the battery in the marina at night, then motor for half an hour till open water sail for the day, motor back up to the marina, Over a period of time of using more than charging, the average capacity got lower and lower, result heavy discharge, limited recharge and sulphation.

Brian
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That is a terrible working regime, very damaging. I'm sure it is quite common, people don't realise the effects.
I suggest the more damaging aspect of it is the prolonged periods of never being fully charged - in fact that is the permanent situation in your scenario - rather than the fact of discharging to flat.
Rather an academic point really. What matters is that this is an excellent way of ruining batteries!
People are often frightened of overcharging but in reality far more batteries are damaged by undercharging.
 
GHA said:
Couple of links...

http://www.researchgate.net/publica...eadacid_batteries/file/d912f50fb37c2249fc.pdf

Pity most of this is behind a Paywall ..
http://www.sciencedirect.com/science/article/pii/S0378775303009340

Edit. And another..
http://journal.esrgroups.org/jes/pa...l0wMOK_cCB_uQpSfA&sig2=qDyQf2SAFXhG6CqAIH_HrQ
Click to expand...


That first paper is very interesting and thorough (bit sad being a battery geek I suppose :redface-new: , but it paid my mortgage for years!)

The abstract of the 2nd one looks interesting too and worth reading by itself. Unfortunately 2 years after I retired, my university library credentials have finally been cancelled and I can't access the full paper.

The 3rd link won't work for me.
 
Plevier said:
That first paper is very interesting and thorough (bit sad being a battery geek I suppose :redface-new: , but it paid my mortgage for years!)

The abstract of the 2nd one looks interesting too and worth reading by itself. Unfortunately 2 years after I retired, my university library credentials have finally been cancelled and I can't access the full paper.

The 3rd link won't work for me.
Click to expand...
Link didn't work for me either :) try this one..
journal.esrgroups.org/jes/papers/4_2_2.pdf

And another one popped up if anyone is still feeling hungry...


http://orbit.dtu.dk/fedora/objects/orbit:88309/datastreams/file_7710966/content

One thing did come up here which I haven't come a cross before, possible benefits from equalising as stratification can promote hardening of sulfation, so a blast once a month may well help but not for the reasons we might think, any thoughts?

Also, equalisation getting rid of hardened Sulphation doesn't seem to be quite as likely as we might like to think.
 
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GHA said:
Link didn't work for me either :) try this one..
journal.esrgroups.org/jes/papers/4_2_2.pdf

And another one popped up if anyone is still feeling hungry...


http://orbit.dtu.dk/fedora/objects/orbit:88309/datastreams/file_7710966/content

One thing did come up here which I haven't come a cross before, possible benefits from equalising as stratification can promote hardening of sulfation, so a blast once a month may well help but not for the reasons we might think, any thoughts?

Also, equalisation getting rid of hardened Sulphation doesn't seem to be quite as likely as we might like to think.
Click to expand...

Yes that link (journal) worked but i don't think it was worth the bother!
The last link (orbit) looks very interesting - but not to the average owner I think!

I am surprised some of these papers place so much stress on stratification. In my experience it's rarely a problem, possibly after prolonged float charge, not on a battery that is being recharged with any vigour after discharge. Also the motion of a boat will soon stir it up.

You're right about sulphation. No magic cures. However with a good operating regime it doesn't become a specific problem, just part of ageing.

Off on hol very soon, unlikely to respond any further to this.
 
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