I'll measure the voltage when my Bettery Tender® (old one, not "plus") on my 400F traditional wet cell Yuasa YB12A-A battery gets to "storage".
I'm curious about the float voltage it reaches but I don't understand how the voltage on your charger leads can be higher than the battery voltage: the on-bike leads should connect (through the fuse) directly to the battery, and if you use the clips rather than the permanent connection cable those clip directly to the battery.
As far as batteries go I go with Yuasa Yumicron® wet cells. They outlast no-name or supplier branded batteries by a good margin in my experience, need only occasional (monthly) attention from the tender during winter storage and a top up with distilled water once - maybe twice - a year to keep electrolyte level between the lines.
That seems pretty good to me.
I have no desire to spend over $100.00 on a lithium battery that also needs a special reg/rect (another $100.00) and can be quickly destroyed by over discharging or charging. The Yuasa costs around $45.00 and mine have usually lasted 5 years.
Yes, wet cells will also be damaged by deep discharging but retain a decent percentage of their performance afterwards. Overcharging just reduces water in the electrolyte to hydrogen and oxygen, "boiling" down the fluid level - easily seen and fixed with a bit of water although it means a problem with the charging system that must be resolved. Lithium batteries can lose most of their capacity when abused even once. AGM batteries may be great, but I don't mind doing battery checks and maintenance and I install the drain tube properly so any drips fall on the ground and not on any bike parts the acid can damage.
The lithium weight saving is hardly significant: as many have said, a diet will help more. And many of the lithium evangelists I meet have installed way oversize tires that add more (and, worse, unsprung) weight than they saved in the battery - what was the point?
