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.
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"....