Good idea to use a real charger instead of the single voltage wall wart that comes with most of these devices. Do note this same, or very similar battery is also the heart of many lead acid jumper packs, and these too will benefit from a 3 stage charger over the single voltage low amperage wall wart.
These AGMs typically recommend charging currents upto 30% of battery capacity which in the case of you 9.5AH AGM is 3 amps or so.
They usually also say upto 14.9 volts.
When deeply cycled time and again, the 3 amp charging rate until ~14.9v is reached at less than 77F, would make the battery happier than a single voltage 13.6v 0.75 amp maximum charger that it came with.
It is not just the recharging time that would be decreased, but the higher charge rate would better be able to return the AGM battery to maximum energy density, and allow it to run the device for somewhat longer during the next discharge.
I cycle a larger AGM battery deeply, and the low and slow recharge to full is not nearly as effective as a higher rate to full. This is evident in higher voltage held during the next discharge cycle, and also on how quickly it can spin my starter motor, and the voltage maintained during engine cranking.
It gives me obvious signs when the high amp recharge is required, and these signs start at about 6 low and slower recharge cycles, and by 10 deep cycles without the higher charge rate the battery almost seems like it is on its way out.
But 40 amps applied to a 50% depleted 90AH AGM battery until 14.5v is reached at 77f, then held for ~4 to 6 more hours, and performance is restored to that nearly as good as when new.
