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Practical Sailor AGM battery report

6K views 13 replies 10 participants last post by  Argyle38 
#1 ·
The latest issue of PS has a report on how real world usage affects AGM batteries.

The bottom line, (correct me if you got a different takeaway) was that standard cruising battery usage of discharging 50 to 60 percent then running the engine for an hour every day has the cumulative effect of diminishing the capacity of the battery significantly maybe 15% to 25%.

Bringing them up to full charge and equalizing seemed to restore the battery's capacity to some degree.

PS is sometimes accused of being too technical and missing real world effects.

I'm interested in what our experience members thing of this article.

Mainsail?

Also what is the deal with pulse chargers? They were not mentioned in the article.
 
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#5 · (Edited)
The latest issue of PS has a report on how real world usage affects AGM batteries.

The bottom line, (correct me if you got a different takeaway) was that standard cruising battery usage of discharging 50 to 60 percent then running the engine for an hour every day has the cumulative effect of diminishing the capacity of the battery significantly maybe 15% to 25%.
Absolutely but this is not anything new. The average sailor has NEVER achieved lab cycle numbers in the real world under PSOC cycling practice.

In a recent battery use survey on Sailboatowners.com with 1151 sailors answering the survey the average overnights spent on-board, where a deep discharge was likely to occur, shows that 89% of the respondents reported 35 nights or less per year with the vast majority 64% being 15 cycles or less.. It was also reported that 59% of all respondents got less than 5 years life from their batteries. This means 175 cycles on the high side and 75 cycles on the low side. This is a FAR CRY from the 1000-1200 cycles many battery makers claim in the LAB.....

Bringing them up to full charge and equalizing seemed to restore the battery's capacity to some degree.
Only the Lifelines could be equalized but in the end it still lost more capacity than the Odyssey TPPL AGM. Why? Hard to say without years more testing. It could however be because the Odyssey was allowed to achieve a higher charging voltage (14.7V vs. 14.4V). The Firefly was also charged at 14.4V but uses patented carbon foam on the grids to limit sulfation. Of course the Deka fell flat on its face and was charged to 14.6V so there are clearly quality differences between batteries but I suspect that the charging voltage does matter in PSOC.

PS is sometimes accused of being too technical and missing real world effects.
This test was specifically designed to MIMIC real world yet be repeatable and comparable between brands. The sad reality is that the battery industry refuses to give us a BCI test for PSOC tolerance. Sad and insulting really..

My gut suspicion is that a deep cycle AGM battery (Odyssey, Northstar & Lifeline) really need to get back to 100% SOC every 2nd or 3rd cycle for the best performance and longest cycle life. Ideally every cycle but that is simply not realistic.

It should be noted that the effects of sulfation happen to all lead acid batteries, not just AGM. AGM batteries are just much easier to test and to show how we are murdering our banks by how we use and abuse them. Flooded batteries can be charged at higher voltages on a regular basis and this can help limit sulfation and they can also be equalized.

The Firefly we know can go 30 deep cycles, with a full 100% recovery, but I suspect a full recharge ever 15-20 days is more reasonable for that battery.

I'm interested in what our experience members thing of this article.

Mainsail?
Seeing as I did the testing and wrote the article (though PS edited much of it and it was a lot of work in back & forth edits to make it accurate) I think you'll not find a more knowledgeable response on that testing...;)

Also what is the deal with pulse chargers? They were not mentioned in the article.
If you are talking about "battery desulfators" (I have also tested them) they are pure snake oil in regards to actually "desulfating" a sulfated battery. They may (strong emphasis on may) be of some slight benefit if starting new but I have seen batteries using them since new do no better than standard chargers, on a regular basis.

More about the testing:

Fighting Sulfation In AGM's - Practical Sailor May 2015

  • All batteries were treated exactly the same using lab grade test equipment and a temp controlled water-bath.

  • They were discharged and charged as we often do on boats thus replicating real world use in a "lab like" environment for closer A to B comparisons.

  • The Firefly was the only battery to survive the testing and recover all of its capacity. Other than the Lithium battery, which was used as a control or benchmark, the Firefly came out on top. PS's caution as "new technology" is certainly within reason, and I tend to agree with it, but the data still speaks rather strongly for the Firefly as a potential game changer for cycling applications on boats. No other AGM battery survived the 30 PSOC (partial state of charge) cycle testing without at least a 6-7% loss in capacity. The worst loss in capacity was approx 30% in just 30 PSOC cycles..

  • The way we use batteries on boats, partial state of charge operation, is murder to them so having a battery than can recover from the effects of sulfation could be a real game changer and far less complicated than LiFePO4.

  • In just 30 cycles some of the AGM batteries lost between 7% and 30% of their total baseline tested Ah capacity.. 7-30% capacity loss in just 30 cycles.. In the real world those 30 cycles would have likely been even more punishing, especially in a hot climate because the time between recharges would often be longer and allow the sulfate to harden more and risk less of it being re-convertible. In the test all batteries had to be treated equally and in the real world the time between discharge and partial recharge varies.

  • It also brings us to a question we did not delve into and that is; these batteries range in lab rated cycle life from 350 cycles to well in excess of 1000 cycles. What good are these lab numbers, and how realistic are they if we don't use our batteries in a lab like manner? The 350 cycle rated battery lost 30% or 1% for every PSOC cycle. Lab cycling tests are not PSOC which is how we use batteries in the real world. I can't talk about the second Deka battery we tested yet other than to say wait for the next issue......

My gut suspicion, after seeing this with my own eyes, is that a deep cycle AGM battery (Odyssey, Northstar & Lifeline) really need to get back to 100% SOC every 2nd or 3rd cycle for the best performance and longest cycle life, but we really already knew this. Ideally every cycle but that is simply not realistic on a boat..

It should be noted that the effects of sulfation happen to all lead acid batteries, not just AGM. The Firefly did form sulfate and lose capacity or "walk down" but it also fully recovered by the second deep cycle with full recharge.. AGM batteries are just much easier to test and to show how we are murdering our banks by how we use and abuse them. The effects of sulfation happen to ALL lead acid batteries, flooded AGM and GEL.

The Firefly we know can go 30 deep cycles, with full recovery, but I suspect a full recharge ever 15-20 days is more reasonable for that battery.

Interestingly the Firefly battery is sulfation recovered by discharging it to 10.5V - 11V then fully recharging it once or twice. This battery behaves entirely differently than other lead acid batteries when it comes to sulfation recovery and high voltages are not needed just deep discharges followed by a full recharge. I did not believe it myself until I saw and tested it. Two deep discharges with full recharges, back to back, results in the best recovery for the Firefly. This is due to the unique and patented carbon foam construction..

I thought you dont *EVER* equalize AGMs or other sealed batteries. No way to replace the fluid lost to boiling.
In general you don't equalize AGM batteries other than Lifeline brand AGM's.. Equalization can work on any lead acid battery but each AGM manufacturer has designed the battery for specific parameters and most have legitimate concerns about "drying" the battery out though equalization/gassing.

My own thoughts on the issue, after years of doing this, are that we destroy our batteries prematurely via sulfation, due to PSOC use, long before we'd ruin them with a periodic equalization.

I have cut open numerous dead AGM batteries only to find them still plenty "wet" but destroyed via sulfation. I suspect there is a fine line of absorption voltage vs. PSOC use but until the manufacturers study this, and tell us what that fine line is, for PSOC operation, we are only guessing at it to arrive at a suitable cycle life. I still default to the manufacturer's suggested guidance...

I can tell you that charging a certain manufacturers AGM 0.2V higher than recommended has resulted in longer cycle life in PSOC operation but I defer to the manufacturer for others doing the same.

The bottom line is that this is an answer best left to your battery maker. I do suggest using the highest allowable charging voltage you possibly can, as that tends to help fight off sulfation.

With most AGM batteries full means 0.5% - 0.3% current acceptance at absorption voltage before they can be considered "full". This is .5A to .3A of charge current acceptance, at absorption voltage, on a 100Ah battery and this can take 6 - 10+ hours to get there AT ABSORPTION VOLTAGE. When you have a charger or solar controller that uses an egg timer approach and times out of absorption at 2 or 4 hours.......????

Yep the problem is deeper than just PSOC.....;)

As I have said many, many, many times AGM or GEL batteries should be installed as a "system"....
 
#6 ·
I've got two sets of batteries on board. Two Group 27 Gels making up the house bank and four 8A4D AGM in series making up a 48 volt propulsion bank. They were installed eight years ago and are still going strong. But, I charge them early and often using a Honda 2000 generator via well regulated battery charges and solar and a wind turbine (48 volt bank). Because I have electric propulsion for auxiliary power I have no alternator for charging. When motoring under electric propulsion when I see battery capacity has dropped to 70% from 100% that is when I fire up the Honda and start electro sailing. I usually stop drawing current from the battery at that point. At my destination I will use the generator to do a full charge on both banks. I use two chargers on the 48 volt bank. One for bulk series charging which get things up to around 94% charge capacity. I then switch to a Dual Pro 4 charger which charges each battery in the 48 volt string individually to full charge. After that solar and wind keep things topped up and no further charging via the Honda is usually needed. I'm aiming for ten years use out of the batteries and so far so good.
 
#8 ·
I just bought a small gel for my 25' racer. It won't be used often or for long periods, mostly just when a race lasts after dark. I chose it because it's maintenance free.

Would it be better for the battery's longevity to recharge it after every use, even though it has only been used for an hour or two, or should I use it a couple times before recharging it?

Also, does anyone have any idea what percentage of it's charge can be expected to be lost just by sitting unused?

I want to be sure I charge it often enough so it powers my lights when I need them.
 
#11 ·
I just bought a small gel for my 25' racer. It won't be used often or for long periods, mostly just when a race lasts after dark. I chose it because it's maintenance free.

Would it be better for the battery's longevity to recharge it after every use, even though it has only been used for an hour or two, or should I use it a couple times before recharging it?

Also, does anyone have any idea what percentage of it's charge can be expected to be lost just by sitting unused?

I want to be sure I charge it often enough so it powers my lights when I need them.
Better to charge it up ASAP after use rather than let it sit around discharged. Just make sure you have a charger that has a setting for charging Gel batteries. It also sounds like you might also do well with a solar panel or two but, again make sure the solar controller you use has a setting for Gel batteries. I have a Morningstar solar controller and it has settings for Gel, AGM and flooded batteries. Been working 24/7 for eight years with no problems.
 
#9 ·
Have 1020ah of lifeline house and separate lifeline start. Have solar and wind running 24/7. It's rare (once every several months) batteries drop to 80% and then run genset until they are back to float. In full cruising mode (radar,instruments, frig/freezer, AP all on) alt. energy keeps up. Boat is plugged in at a slip when not cruising for ~1wk/m. Boat is in operation except for bottom paint hauls.
After one year sensors (phillipi) tell me batteries at 980ah at float.
?Can I expect same annual decline in future years?
Would adding more alt. energy such as hydro generator prevent this?
 
#10 · (Edited)
The way you are treating your batteries should result in decent life. That said...

While the Phillipi is a very nice Ah counter it is still just an Ah counter. All the misinformation, programming errors, false resets etc. still apply. This device can not predict your Ah capacity or your Ah capacity loss. Anything it is showing you is 100% theoretical and usually not very accurate unless you've kept up with yearly Ah capacity tests etc., adjusted all the settings regularly and manually re-synced regularly.

The only way to know your true Ah capacity loss is to physically conduct a 20 hour capacity test. Of course if you did not start with a baseline Ah capacity then this % loss may not be precisely accurate but it will certainly give you the true Ah capacity at your batteries current life state..

I know this article is a LOT of information overload but do take the time to read it because it may give you a glimpse into how these magic boxes actually work..

Programming A Battery Monitor
 
#12 ·
Great article, Maine.

Those Firefly batteries seem almost too good to be true. (Have to deep discharge them to re-gain full capacity?! Hell yeah, I can do that! "Ice cold drinks tonight baby, the battery is getting low!") Right now, however, they are fairly pricy compared to even Lifline AGM's.

You said that you were already installing him for customers. How long have they been out? Do they seem to be holding up in real world usage?

Have you given any thought to their cost/amp hour over the expected lifetime of the batteries, i.e. is the extra cost potentially worth it over the long haul?

Thanks,

Argyle
 
#13 ·
Great article, Maine.

Those Firefly batteries seem almost too good to be true. (Have to deep discharge them to re-gain full capacity?! Hell yeah, I can do that! "Ice cold drinks tonight baby, the battery is getting low!") Right now, however, they are fairly pricy compared to even Lifline AGM's.

You said that you were already installing him for customers. How long have they been out? Do they seem to be holding up in real world usage?

Have you given any thought to their cost/amp hour over the expected lifetime of the batteries, i.e. is the extra cost potentially worth it over the long haul?

Thanks,

Argyle
The Firefly certainly was the stand out in terms of fending off the effects of sulfation. Based on those tests and seeing it for myself, I am extremely skeptical, I will likely be installing a lot of them.

Nigel is using the Firefly on his own boat and been quite impressed. He never went above 80% SOC all last year and at the end of the season they recovered 100% of their as new capacity.

Last August he discharged his Firefly bank to 38% SOC and came home to Maine. After 9 months at 38% SOC he arrived on the boat a about 9 days ago, charged the batts, cycled them a bit, and then capacity tested them at the C/20 rate. They were charged at 14.4V and this voltage simply held over night. Nothing really special, he just held them a bit longer at absorption voltage. They are 110 Ah rated batteries and after sitting at 38% SOC since last August (NINE MONTHS) May 20th 2015 they delivered 110Ah's of capacity! :eek

That is damn impressive stuff and makes the PS PSOC test look like child's play for the Firefly.. I am sure I don't need to explain that this type of abuse would have been guaranteed death for any other lead acid battery I know of....

I can't speak to long term projections but the PSOC test we set up should be a good predictor of future performance for boats where PSOC operation is the reality. The batteries are not inexpensive by any means, about $425.00 for a Group 31, and case sizes are limited, but for me they bridge a gap between AGM acceptance performance, GEL cycle life and still are a lead acid battery so a drop in replacement is easy. This is a small company and demand is currently slightly ahead of production so they can be a bit tough to get.

Like any batt only time will tell but I suspect these should easily outlast most current AGM's on a boat where PSOC use is a realty.

I will still obviously install Lifeline & Odyssey too depending upon boat owner budget....

Oh and the reserve bank on my own boat will be a Firefly...

As for cost these batteries are suggested to be cycled to 80% DOD and they support voltage very well doing so. This brings the cost per usable Ah down and with a lab cycle life of over 1000 cycles to 80% DOD this eclipses the Odyssey to 80% DOD by about 600 cycles...

The cost of batteries can not be judged on the box price alone. Ah's, projected cycle life, and lifetime watt hours or Ah's delivered are what determine actual battery cost.

Yest the box price is higher than other G31 AGM's but not by a huge margin. When you consider that the other batteries should only be cycled to 50% DOD, to maximize cycle life, and don't handle PSOC use as well, it certainly makes a strong case for these batteries not costing as much as they appear to when judged only on the "box price"......
 
#14 ·
Wow, thanks for the update. Calder's real world testing has to be considered legit. The guy knows a thing or two about on board electrical systems.

My Lifelines are getting a little long in the tooth, but very light usage should mean I can get a few more years out of them. Will be watching this technology very closely.
 
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