I just installed a lition battery in my '09 XC500. A little more expensive, however, warranty is for 5 years instead of 1. Or 6 months. Manual says as long as it's charged once a month, no need to keep a battery tender plugged in during winter months.
One quirk about it is cold weather starting. Instructions say 1st startup in morning, even normal warm one, turn on for 30 seconds before engaging starter to wake the battery up.
On cold morning, turn on for up to 5 minutes, depending on how cold, to warm the battery before engaging starter.
On a recent s'camping (scooter camping) trip, I neglected to allow it to warm up and scooter almost failed to start. Morning was around 44 degrees at Mission Tejas park in East Texas. Lots of tall pine trees in the Davey Crockett National Forest.
I haven't had the batter installed long enough to give a thorough opinion. Yet. I just put nearly 900 miles on the scooter over a 4 day period. It was loaded with tent, food, stove, bedroll and clothes.