Opted for Yuasa after reading hear and other on line comments.
Have always kept them on a trickle charger. Current Energizer shows 12.74 volts but under load drops to 12.2.
Typically, more than 5% voltage drop under moderate load tells that the lead is losing free electrons. This is normal wear, as opposed to 'sulphation' issues, which is when the lead gets oxidized by other elements like impurities from the lead alloy used, itself. The purer the lead, the less there is to attack it. Keeping a steady trickle charge on the battery tends to break the lead down on the (+) side of the plates, which is where the electrons exit to circulate thru the charger (electrical current) as the 'new' electrons (from that charger) attach to the other face of that lead plate. The new arrivals are not chemically identical to the original lead, so some inefficiency results from being left on chargers constantly, shortening life overall. We learned this back in the 1960s and 1970s.
This led to the spiral-wound 'minichamber' technology where the chemistry is actually captured in hundreds (or thousands in car batteries) of little cells, rectangular chambers that were punched into lead sheet, making them look perforated with little rectangles. Then the conductive metal layers (+ pole and - pole) were laid onto the perf'ed lead, filled with acid, and rolled up into a shape like a soda (or beer) can. These became known as the '6-pack' batteries in the 12 volt versions, as each wrapped can was 2.2 volts after charging. These versions last decades, in my experience (heck, the one in my motorhome is 30+ years old and works fine, still) and if they hadn't been "knocked off" into something cheaper (using worn, recycled lead) in Mexico when the bike versions appeared around 2005 or so, they would still be great today. The Japanese picked up on the closed-cell construction, though, and used fiberglass mat in little rectangle shapes to hold the acid in between two lead sheets (sort of an inside-out version of the wound cell) and the AGM version was born. For bikes, this is about the most efficient battery we can get right now.
