The charging voltage vs current is puzzling.
The charging recommendations I have found are usually max 1/10 of the battery capacity which is 14Ah/10=1.4A.
My CTEK MXS 5.0 charger has AGM mode, but not current limit as its motorcycle mode of 0.8A (14.7V)
Specified current for batteries of 14Ah and up is 5A (14.8V), AGM mode same.
Speaking as one who had to design such chargers in the past, it is a bit of tomfoolery to get the various types to charge correctly, especially if they are dead - or if they were just built in the factory.
The old lead-acid type will charge with anything of a higher voltage that is attached to it, even another battery. This can reach dangerously high currents in certain situations, too, if the charged-up battery is a high-capacity (big amp-hours) and the dead one is not - like a car battery vs. motorcycle battery, with the car running: I'm sure you've heard what happened with those! If this design has enormous utility and forgiveness of abusive use, it also has the short-life issue unless the lead is pure as the driven snow.
The Ni-Cd types are the most finnicky: they can only be charged with a limited amount of current of a narrow voltage range, which must start low, end at the desired voltage, and stop charging when the battery is 'full'. If the charger is left on, the battery then begins to degrade: this was part of Apollo 13's problems. In that situation, their 2 main Ni-Cd 'backup' batteries were left on chargers at Cape Kennedy by technicians who didn't read the (48-page) User Manual that the kids at CU Boulder (Colorado) wrote when they built the batteries: it said, on page 20-something, to 'never leave the charger connected when battery voltage rises above full charge'. (This Boulder group also built the fuel cell that blew up, with similar instructions that got ignored, causing the whole mishap.)
The AGM type is a flat-plate, cheaper-to-make version of the best type of battery (IMHO, which I'll get to in a minute...) that is the result of trying to retain some of the absolutely stellar performance of the closed-cell, permanently-wetted, controlled-chemistry encapsulated-chamber lead-acid recombinational battery invented by Gates Energy in the 1980s. To that end, the AGM contains thousands of tiny cells in the glass mat that do not heat up much when charged or discharged, simply because there are so many and they are all at relatively low energy. Lately this tech has been bastardized by the Chinese and we are seeing AGM batteries that can heat up enough to pop ("explode") and scatter their chemistry everywhere simply because the natural limitations on charge rate have been removed and a solid-state 'brain' has been implemented to control charge rates inside the battery. BAd choice: Chinese semiconductors are made from the garbage left over by places like Malaysia and our own Silicon Valley, so they frequently don't work as planned - almost 30% of the time, in fact. (End of rant...
) The better- quality AGM batteries are good performers: some who have not worked with the all-time best (and my favorite) call these the best battery for their applications.
BUT...once you have worked with the famous "6-pack" wound-cell, closed-chemistry, permanently-semi-wetted, recombinant-technology Gates Energy cell (now made in Kansas by Enersys, invented here in Denver at Gates, circa 1986) you get to see what a battery can REALLY do, and then you wonder why anyone would ever want to use anything else. I have one that powers the living area of my motorhome, since 1996, that was a 'factory second' at the old Gates plant where I helped modify their old semi-manual control system into a PLC-controlled one in those days. During the startup of the new line, one battery was left in the heat-sealer too long when someone didn't remove it following an Emergency-stop test, and the top of it got a little bit melted - cosmetic damage - so they had to reject it. They let me take it! I went home and modified my motorhome's battery box a bit larger to fit it, and it's been in there ever since. It works perfectly despite not being used much out on the road in the last 10 years: sometimes I use the motorhome as a 'dry storage' space for some of the bikes I work on - like their tanks and side covers when their engines come out. You can use any type of battery charger on it, and it will self-limit on charge and discharge rates to 300 amps, but will accept as little as the 150mA solar charger that I plug into the motorhome's cigarette lighter to keep it from dying of neglect. That is a charge-turndown-ratio of [300,000/150]=2000:1, which means it would be nearly impossible for someone to overcharge one to catch it on fire, nor undercharge it so it sulphates. Instead, if it goes 'dead' it simply becomes inert until a new charge is applied, when each of its tens of thousands of tiny cell battery chemistry cells re-enjoin the trapped ions in the lead and recreate the acid chemistry. They cannot sulphate because the trapped-cell liquid instead turns to a [dirty] water of dissociated ions for lack of oxygen, awaiting some excess electrons to reform the cell. A VERY cool bit of tech.
