Or, you could buy a better charger
Want to know more about why we're running an AGM battery and how to maintain it?
Battery University-201: How does the Lead Acid Battery Work?
BU-201a: Absorbent Glass Mat (AGM)
AGM has very low internal resistance and is able to deliver high currents on demand, offers a relatively long service life even when deep cycled, is maintenance free, provides good electrical reliability, and is lighter than the flooded lead acid type. While regular lead acid batteries need a topping charge every six months to prevent the buildup of sulfation
, AGM batteries are less prone to sulfation and can sit in storage for longer before a charge becomes necessary. The battery stands up well to low temperatures and has a low self-discharge
AGM charges up to five times faster than flooded and offers 80% depth-of-discharge (flooded is 50%). AGM is the preferred battery for upscale motorcycles because it's sealed reducing acid spilling in an accident, lowers the weight for the same performance, and allows installation at odd angles. AGM batteries are sensitive to overcharging. A charge to 2.40V/cell (and higher) is fine; however, the float charge should be reduced to between 2.25 and 2.30V/cell (summer temperatures may require lower voltages).