When did you get that 14v reading? Right after starting. 5 minutes later?
12.2v is generally considered 50% charged, if the battery were 77f, and had not seen any discharging loads or charging sources for many hours. Resting voltage. Surface charge voltage retention can last many many hours after charging, and likewise it takes a while for voltage to rebound after a load is removed from a battery, but it does not take as long to rebound after loading as it does to dissipate after charging. How fast it rebounds can be an indicator of health, but temperature plays a huge part too, and comparisons on the same battery are really needed to make any declarations with any degree of certainty.
If this 12.2v morning battery were brought to me, I'd hook it up to my 40 amp adjustable voltage power supply set to 14.7v. I'd see how many amps it accepted while it rose towards 14.7v.
if it sucked up 40 amps for more than a few seconds it would be well less than fully charged.
if it rose nearly instantly to 14.7v, I'd see how quickly those amps tapered while held at 14.7v. If they tapered quickly I'd consider the battery nearly fully charged, but badly sulfated.
If they dropped relatively quickly to ~5 amps but leveled off and took another 2 hours to taper to less than 0.5 amps I'd say it was about 85 to 90% charged and partially sulfated and likely able to have a good portion of that capacity restored with a prolonged recharge at higher voltages while being relatively closely monitored for temperature rise.
Once i got it fully charged, determined when amps either stopped tapering for more than an hour, or started rising when held at the same voltage, I'd likely use my 16 to 19 amp 12v air compressor on it, see how much voltage it maintained, and how long it maintained it. If it maintained over 12.4v after a minute, I'd be pretty happy. If it fell below 11.8v I would not.
While the 16 to 19 amp air compressor is not a 'true' load test, it is a valid test when compared with itself after a discharge /recharge cycle. Seeing how low the voltage falls when cranking the same temperature engine is a better test for comparison, but the temperature variable is less easy to control. Here is where a digital voltmeter rigght with sense leads right on the battery and watched closely every engine start is quite revealing as to battery performance/
But of course I do not know the size of your battery, I am assuming it is a group 24 size or around there.
If it was obviously weak, I'd discharge it to about 10.5volts under a 15 to 20 amp load, then I'd promptly recharge it with about 20 amps until it reached 14.7v, unless started heating rapidly, then I'd lower the amperage and keep the battery from exceeding 95 to 100f. I'd bring it to 14.7v( 77f) and hold it there until amps stopped tapering and either got to 0.0x, or started rising again.
It is highly likely, once removed from the charger, and let to cool down, it will perform better, hold more voltage than it did that first time powering my air compressor and it will likely also recharge to full faster from the same level of depletion the next time too. A hot battery will perform better, so allowing it to cool is necessary for a valid comparison.
If it did not perform any better, I'd be surprised, whether another discharge/ recharge cycle would be performed would be decided on how it performed, how old it was, and its temperature, and the intended use of the battery, Climate, size of the engine it is being asked to start, and the main driver's ability to safely jumpstart it and thier financial ability to either replace now or if 2 months from now would really be better.
AGMs like high amp recharges, Disregard the 'trickle charge it overnight' mentality on reads so often on automotive forums, especially when they are deeply discharged. Go as high as 30 amps for 100Ah capacity of battery( group 27/29/31). Your alternator would exceed this amount greatly , even if relatively briefly, after a jumpstart, but most lesser $$ AGM manufacturers say to not exceed a 30% charge rate when using a plug in charger.
Some top quality$ AGMS like Odyssey and Lifeline AGM say more amperage is better, always, Odyssey spec'ing no less than 40 amps per 100Ah of capacity and Lifeline no less than 20 when deeply cycled. the deeper the discharge the more important achieving the proper recharge becomes..
I have two smaller Chinese made AGMs, the UB12180 and the UB12220, 18 and 22 amp hours respectively. These batteries often come inside lead acid jumper packs. Though of course Lithium jumper packs are shinier these days. These batteries say 5.4 and 6.6 charging amps maximum, respectively. I have greatly exceeded these amperages without issue, or excessive heating. But the latter is the concern and why they recommend a maximum charge rate, and I do not quadruple this 'recommended' rate every time, only double it.
Every new AGM or flooded battery I have acquired for myself or clients or friends whether starting/dual purpose, marine/ deep cycle, has performed better after discharging them a fair amount, and then recharging them fully at a initially high rate. Every one. Both my Northstar AGMS have failed to achieve their manufacturer spec'd full charge resting voltage(13.0v+), until I cycled them deeply and high amp recharged them the first one refused for 7 shallow cycles over 2 weeks to exceed 12.84v resting, until I discharged it to 50% and then fed it 25 amps until 14.7v then held it there until amps tapered to 0.4.
After a few deeper cycles and high amp recharges to full, not only do they rest above 13.0v, but their engine cranking ability is noticeably more powerful, well into the scary fast realm.
I think that AGM'S that do not get this initial 'break in', never live up to their potential cranking amp, or longevity.
Those who deep cycle AGMS in boats or Rv's, and rely ONLY on low and slow solar to recharge them, usually get very poor life from them and whine and complain even if they have enough solar to recharge them fully regularly. That high initial amperage rate when they are most deeply discharged is required to force the electrolyte through the glass matting. Often the manufacturer denies warranty coverage after the owner describes their charging source that is incapable of either achiving full charge regularly or achieving a minimum recharge rate regularly.
Those who deep cycle AGMs, and plug in undersized chargers, also report disappointing lifespans from them, and many go back to flooded batteries as they seem less finicky about low recharge currents..
Deep cycle flooded batteries manufacturers declare they will not develop their full potential capacity and performance( voltage maintained under load) until they have been cycled 20 to 50 times, assuming discharges no more than 50% and prompt recharges to a true full state of charge, 100%, not 95 or 98% but 100%.
It is hardly outside the realm of possibility that both CCA and long term performance/longevity of ALL lead acid starting batteries can be improved upon with at least one and perhaps a few discharge/recharge to full, cycles, before just dropping them in a vehicle and letting the vehicles charging system 'take care' of them.
Every time I have gotten a new AGM or flooded battery, and tried to charge it fully, amperage has not tapered to the full charge prescribed level on AGMs, and with flooded batteries specific gravity as measured by a turkey baster style temperature compensated hydrometer, did not rise to the expected levels. Amps would not taper there(AGMs), and specific gravity would not rise there (flooded) until the battery was discharged to the 12.2v range or less under a significantly sized load, then recharged.
This observation and experiment has been easily repeatable, and is now expected with many years of experience, and many dozens batteries I acquire and install for friends or clients. I wont let either friends or customers just install a new battery and drive off. Usually both come to me when their battery is questionable and I either stretch it back out to maximum remaining functioning capacity again, or start bugling taps, after performing experiments on them. I tell close friends to not have Ap stores install the new battery but buy it and bring it to me, and I'll install it gve them the core charge and return it for them, or perhaps try a few times to recover its capacity with extended charges and equalization overcharges gaining valueable experience in the process.
New batteries flooded or AGM get their initial voltage measured, then put on a charger for a period of time until it seems to stop taking amperage, then discharged well below 80%, then charged with no less than 20 amps per 100Ah of capacity. If they are lifeline Northstar or Odyssey, no less than 40 amps per 100Ah of capacity
My last Northstar group 27AGM battery lasted over 6 years, and accumulated more than 1200 deep cycles, as well as accruing many thousands of engine starts. When it became too weak to start my warm engine when very nearly fully charged, I removed it, moved it to workshop duty, and replaced it with a group 31 400$+ Northstar AGM with 103Ah of capacity and 1150 CCA. Its a Beast of a lead acid battery and you can bet your hairy hindquarters I recharge it properly, often, and use much of its capacity regularly too.
Since AGM's have developed a 'superior battery' reputation, mainly through marketing and their pricetag and uninformed consumer friends, manufacturers have been finding ways to make them ever cheaper, especially for intended use as starting batteries, which is a cakewalk compared to when they need to both deep cycle AND then start engines. As a result the AGMS one gets for perhaps only 50% more than their wet/flooded counterparts, are not very high quality. They have neither greatly higher CCA figures than their flooded brethern, nor lesser self discharge figures of higher$$ higher quality AGMS. Their main advantage is the lack of corrosive fumes. Don't think that AGM is therefore always superior, often they are just a bragging rights maintenance free battery, that lives a shorter lifespan than their wet/flooded counterpart that cost 1/2 to 2/3's as much, especially when they are recharged only by the vehicle.
A good AGM battery can be quite superior in performance and longevity, when recharged properly, but they are not immune to abuse and will last only a tiny percentage longer than their less quality brethern, when chronically undercharged.
How long they ultimately last is determined by how well they are recharged, their average state of charge and their average temperature, and vehicles do not care about achieving maximum battery longevity, and very very few vehicles will actually ever truly fully charge a battery.
