I am on my second Northstar AGM battery, the first was a group 27. When new it read 12.84v off the shelf, and northstar's rather limited spec sheet said full charge resting voltage should be above 13.0v. I kept trying top charges withut a deeper discharge, and it would never rest above 13.0v, until I deep cycled it and then applied 25 amps until the so called smart charger shut off, and then let another charging source hold it at 14.4 a bit longer. From that point it was 13.06v full charge rested
back then Northstar Spec'd 14.44v Absorption at 77f. Their documentation never impressed me. I started following Odyssey's recommendations as to charge specs, as well as those by some highly experienced marine electricians with gobs of experience using 14.7v absorption on TPPl AGMS in deep cycle duty.
I got over 1200 deep cycles over 6 years out of that northstar. 6 years is no benchmark, but 1200 truly deep cycles, about 100 of those to 30% charged and perhaps even a bit less, over 6 years is. There is of course many thousand engine starts and likely a thousand shallow cycles to 80 or 85% as well. the amount of KWH this battery delivered over those 6 years was downright impressive.
I replaced it with a group 31 Northstar agm and the highest voltage one on the shelf out of 6, was only a disappointing 12.74. I did not really stress this and immediately drained it to about 50% State of charge, and promptly applied 40 amps to reach 14.7v held it until amps tapered to close to 0.5, and then and 5 hours off the charger, unloaded, it was still reading 13.17v. I did not wait to see what it would have dropped to. Its been in continuous service ever since and I am not sure what its true full charge resting voltage is, but I expect it too is over 13 volts
In 2015 I got a Lifeline GPL 31XT, fresh from the factory in West covina for a friend's portable powerpack I was hired to make. it read 13.12v, and I brought it to 14.4v, and amps never tapered to 0.62 which is 0.5% of 125 amp hours. I knew new batteries, at this point, to behave oddly, and cycled it, then again, 40 amps at 14.4v and this time amps did taper to 0.62 @ 14.4v, and I removed charger and battery sat for a few days. When I checked voltage at was 13.23v. I wound up using the battery, drawing 2.3 amp hours from it, and did not immediately recharge it, but two days later it still read 13.16v.
More recently I got 8 lifeline GPL-4ct's for a boat. They were about a month old on delivery, each 6v battery measured 6.56v +/- 0.02v when I opened their boxes. That would be 13.12v when wired in series as a 12v battery. I've read Lifeline's PDF many times but I've no recall saying they should rest fully charged over 13.0v.
The point being, that 13v+ resting voltaeg on AGM batteries At least TPPL and Lifeline/Concorde AGM thick positive plate deep cycle batteries, is common.
I've no personal experience with Full river's TPPL offering, just became aware of them, but higher full charge resting voltage can be manipulated with higher electrolyte density and most AGMS are said to be 1.300 or higher whereas most flooded batteries are in the 1.275 range unless intended for tropical locations where 1.265 is more likely.
Pretty sure Odyssey claims 12.8 is full charge resting voltage. I've little experience with Odyssey AGMs, but do respect them greatly.
The other two batteries I own and have been the sole cycler thereof, since they arrived, are just small Asian made AGMS, UPG or UB batteries, commonly installed in lead acid jump starters. one is 18Ah the other is 22AH. both werer 12.84ish on arrival and a few months old. Ther Ub12180 holds 13.16 several days off the charger, but then seems to lose 0.02v per week disconnected from everything. The newer UB12220 holds 13.14v+ several days off the charger, and there after has the same apparent self discharge as the Ub12180.
Either of these batteries, and the Ub12180 is now 2.5 years old, can start my 5.2 liter 2 week cold v8, by themselves, showing just how little CCA is actually required to start an engine, even a relatively large one, and just how degraded a 500CCA( when new) battery can be before it can't do its job.
The UB12180 does take much longer to actually drop to 13.16 than the Ub12220 does to drop to 13.14v after removal from charging source. The newer 12220 drops to 13.14 in ~15 minutes, the older Ub12180 takes hours.
So there is two more batteries which have resting full charge voltages over 2.2 volts per cell.
I often use these batteries to power lights or fans in remote locations, sometimes briefly, but will use my wattmeters to see just how many amp hours I pull from them. I can pull almost 2 amp hours from either battery, and voltage will have dropped to as low as 12.5 when powering the loads, but still rebound, without a charger applied, to over 13 volts.
The spec sheet for either battery says nothing about an resting full charge voltages over 13. it specs your 2.2 volt per cell as maximum, or 12.8v, yet I see well over this, on multiple different voltmeters, even when discharged slightly and voltage allowed to rebound, and this is NOT in hot ambient temperatures and a battery hot off the charger.
Heck i just went out and checked them, and neither have seen a charging source for more than 2 weeks and one was 13.06 the other is 13.12v, but now both are connecte to my power supply and are 13.6v, though i did not bother seeing how much amperage they are consuming at that voltage..
Many times over the years we have butted heads regarding lead acid batteries JHzr2. You seem to be the defender of smart chargers, after I call them out for their chronic undercharging behavior.
This is Bitog, there are hundreds of thread titles starting 'what is the best...whatever, not what is good enough..... whatever.
Ideal battery longevity is achieved by keeping the battery cool, not overdischarging it, and promptly returning it to the highest possible state of charge after any level of discharge, not 92% not 97%, but a true 100% state of charge. Undisputable fact.
You seem to say that 98% charged is good enough, as if that is fact, and imply what you consider is good enough, is indeed fact and good enough for everybody, but that is only your opinion.
For those of you who want to establish 'good enough' for themselves, regarding battery charging, you need to know what is ideal, and how to achieve this. This is the info I try to relate, from many years of experience with many different batteries and close observation of them as they age, on many different chrging sources, using tools and interest to measure and refine.
The green light on a smart charger could very well be good enough, for perhaps a majority of readers here. They are only batteries, only rented, and doomed to failure no matter what, the only variable being time to failure. Most readers here can get a new battery at 20 different spots within a 15 mile drive, or delivered to their doorstep the next day. Even without a warranty to totally or partially cover the cost, it is not a budget breaker for most. Certainly not worth the effort acquiring an adjustable voltage powersupply, hooking up ammeters, voltmeters, amp hour counters dipping hydrometers, making graphs, doing experiments, taking notes, keeping records..its just a battery easily replaced, why bother?
I never meant to imply every person needs to do this, only that if they were to actually do it, they would find the smart charger falls well short of achieving a true 100% state of charge, as its marketing implies.
I ask myself this often, why I go through the effort, when replacement more often is less stressful and easier, even though my batteries provide much of the electricity I use and a significant percentage of their recharging is acheived largely by the sun or my alternators. Their lifespans are important to me, not only to get my money's worth, but to not add any more than I have to to our landfills and atmosphere. Our disposable society, where everything is just thrown away when convenient with little thought to the energy used to make it, or what happens to it after it is of no further use to them disgusts me on so many levels, and makes me ashamed to be a part of it.
So many years ago, tired of having to replace batteries, warranty or not, often, I was bothered by them failing prematurely, and decided that I would get as much possible life from them, and began the process of acquiring the knowledge and data and tools and experience in order to do so .
I got a 'smart charger' used it often, with little improvement in battery longevity in a deep cycle application and got irritated when I'd remove 35amp hours from a 115 Ah battery, and see only 12.15v under a 1 amp load. From that point watch the battery degrade faster and faster and become become more and more useless to the point it was a waste of time and electricity trying to charge it as so much was turned to heat and hydrogen and oxygen. I did blame the battery mostly, rather than my charger, as I was still a fool.
When I got a newer heavier more expensive marine battery from a respected manufacturer, within two weeks of cycling it, was very dismayed at the performance, which I measure by voltage retained with x amp hours removed under X amount of load, which I watch closely and have for many sets of batteries over many years.
While i had resisted previously, I got a good hydrometer, temperature compensating, and saw my so called smart charger, was only returning specific gravity to 1.225, which is still in the red, when it would switch from absorption voltage, to green light float, and 10 hours held at float would do absolutely nothing to further raise specific gravity, but that green light was shining away saying all was well.
I'd restart the charger. it would go upto 14.7v for a while, then drop back to float. 1.227, Again restart, 1.229, again 1.231, on and on.
i could not get the smart charger to stay on and maintain 14.4 or higher volts, and I could NOT fully charge it, and the performance during discharge was extremely disappointing. I was dismayed enough I was again blaming the battery, I took it back to the distributor who of course put it on their carbon pile load tester and their midtronics impedence tester, and it read good, stil lhad higher than the spec'd CCA and they were like, no warranty for you.
I had no way to actually hold voltage higher for longer, other than to set my solar controller absorption and float voltages to 16, and make sure the battery was 'fully charged' by 10Am when the sun got strong enough to push the battery upto 15.5+ volts.
The thing was fizzing up a storm when I did so, but the specific gravity was rising, and late afternoon the specific gravity was 1.280 on almost all the cells.
That night the voltage held during discharge was respectable, but the next night was not as good, nor the next, and it kept walking down. My solar was inadequate and often I would plug in and use the smart charger. same results as before, it would simply quit when specific gravity was in the red, and multiple restarts would do little to nothing to further raise specific gravity, as it would keep reverting to float voltage i less than 10 minutes, over and over.
I tried my different smart chargers, the BM 12248 being one of them, with teh same results, and returned it to my friend as 8 amps was just too slow for my purposes and SG was reading even poorer when it switched to float.
I then got a cheapo LEd power supply, adjustable voltage and wattmeters/ammeters, and was able to hold the battery as high as 15.43 volts with it, and I was able, using this power supply, to max out the specific gravity, but it took many many disappointing hours to do so. Dipping the hydrometer often.
That cheapo power supply did not have current limiting on overload and a depleted battery would easily overload it. It would be able to feed as high as 38 amps into the depleted battery, but over 36 amps it made this weird clicking sound, so I limited voltage to keep amperage just under 36, and kept raising it as the battery charged.
Obviously this baby sitting of the adjustable voltage power supply through bulk stage, until absorption voltage was reached, became inconvenient, so i would use my smart charger first, and when I noticed it had quit absorption and reverted to float, I would put the adjustable voltage power supply on it set to 14.8v, with its amp hour counting ability and let it go. Never, not once, did it not require at least 1:45 more time at 14.8v before specific gravity maxed out, and often it was 4 to 5 hours more at 14.8, after removing it from smart charger and putting it on adjustable voltage power supply.
this 130 amp hour US group 31 marine battery, would require the power supply return no less than 15 amp hours into teh battery, in order for specific gravity, adjusted for electrolyte temperature, to reach previously established maximums. The Smart charger was consistently shutting off with teh battery only ~90 to 92% charged, and it was pointless to try and get specific gravity any higher using the smart charger.
I borrowed other so called smart chargers, and they did the same thing, stopping holding absorption voltage well before the battery was fully charged, and switching to float where specific gravity never rose any more. The adjustable voltage power supply was required to hold them at 14.8v for several hours after the smart charger gave up, to even get the cells to 1.265, and as the battery aged it took longer and longer to reach 1.265, and 1.280 was only achievable by holding 14.8 for several hours, then bumping voltage to near 15.5v for no less than 45 minutes.
to be continued...