The % displays on Schumacher chargers, and most 'smart' chargers are to be taken with a huge grain of salt.
They are based entirely on battery voltage when the unit is first attached to a battery. Battery voltage is only accurate on a well rested battery, one that has not seen any charging nor discharging for quite some time. One battery might rest fully charged at 12.62 and an AGM might rest fully charged as high as 13.16v, and be only 70% charged at 12.62v. Battery Voltage is not like a fuel tank gauge, it is a general indicator at best and only accurate on a well rested battery when the full charge resting voltage has previously been determined when the battery was newish. There are alos several variables which make any instantaneous voltage reading highly inaccurate in guessing at state of charge.
There is no magical device which can be attached to a battery and give instantaneous state of charge percentages with any degree of accuracy. A true battery monitor/ columb counter counts amps into and out of the battery and needs a known full charge, as a starting point, and then somewhat regular calibration, as some batteries need 105% of the juice taken out to return to full and some others might need 130% or more and this will vary with temperature, average depth of discharge and time since the last true full charge and even the best of battery monitors are likely only 95% accurate and they will drift out of whack with time.
And smart chargers are not designed to truly fully charge each and every battery, they are design to never Overcharge any battery. They usually fall well short of a true full charge, Which usually is inconsequential to most driver's batteries, and more than good enough for most, especially when product pride and marketing are considered.
When one has the tools and the aptitude and the gumption to insure a true full charge of a hard working lead acid battery, in an attempt to insure maximum longevity, one can see just how short 'smart' chargers fall. Most can't, won't, never do, and remain proudly ignorant.
But most engine starting batteries have a relatively easy life and don't qualify as 'hard working' so the 'good enough' bar is quite low.
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I've had a relatively young inverter look like it was dipped in a salt bath, yet never having gotten wet, not even used much. Other electronics located in the same area have been fine for a decade or more.
My schumacher sc2500a 'intelli' charger is batcrud crazy. I can't trust it and leave it unattended, as it will significantly overvolt a battery sometimes, yet others give up and revert to float prematurely, well short of anything even remotely considered fully charged. Very rarely does it ever actually bring the battery to the 95% State of charge range without intervention. I don't trust it and rarely use it, and would go insane if I were trying to figure out what it was thinking/attempting by its Bizarre behavior.
I think it escaped a mental institution then started dropping acid and now thinks it is an orange in the corner and every battery is trying to peel it. So when i see someone put any faith in their Schumachers % display I get a chuckle and see an orange with red numbers followed by a %.
Some Caig Deoxit d5 can sometimes act like magic electrical juice. I've had it return items to function for no logical reason I could determine. I tend to spray the circuit boards of salt exposed items to Caig DeOxit S5 Shield spray, but do not get it on the soft silicone boots inside electrical connectors as they tend to swell and make refitting them quite difficult. Its pricey but great to have on hand for any electrical connection. Electrical connections need lube too. What looks pristine might make a d5 dipped cotton swab turn black from pink.
Good luck. I think the battery minders with the optional temperature sensor are where I would go for a maintainer. My buddy has the 12248 though i think it has failed now. I used it on some marine batteries that were chronically undercharged with no Improvement.
Now if I am asked to revive a battery I put it on an adjustable voltage power supply and watch amps respond to different voltages( electrical pressure) to get an idea where its at, then discharge it nearly fully, taking note of how much it had to give for how long, then charge it at a relatively high rate until amps taper to low levels or temperature gets above 105f. The next discharge almost always proves to have gained over that first one, and a second one might or might not be beneficial. Often i can see the battery is not going to respond as it has nothing to give and few amps take it to absorption voltage, and holding it at absorption voltage only heats it excessively.
In the manuals of top battery manufacturers, granted they are for deep cycle lead acid applications which is fairly different from starter battery usage, none of them say any pulse desulfation chargers are beneficial in any way.
http://lifelinebatteries.com/wp-content/uploads/2015/12/6-0101-Rev-E-Lifeline-Technical-Manual.pdf
https://rollsbattery.com/public/docs/user_manual/Rolls_Battery_Manual.pdf
If you read and digest even 1/4 the info in these two manuals you will understand more about lead acid battery care and feeding than 99.99% of the population.
if I had a fleet of batteries to maintain, I would have an adjustable voltage power supply set to 14.7v, and lots of 18AWG zip wire and anderson powerpole connectors, and have it on a timer for 10 minutes a day in winter and set to 14.2v in summer.
Long term float at an incorrect voltage is no good, and the ideal float/maintenance voltage is different at different temperatures and different for different batteries, and different for the same battery as it ages.
One size does not fit all. One size fits none perfectly, despite the marketing claims saying otherwise