I bought a Battery Tender model
BTL14A240C from Amazon.com in spring 2015. I just used some wood cut up and painted to use as spacers in the battery box. Someday I'll fab up a custom battery box. I've used Lithium batteries for several years on my other motorcycle.
I believe this is just an 8 cell lithium iron phosphate battery (4s2p)
The thing to keep in mind about these lithium batteries being sold for motorcycles is that they are significantly smaller capacity batteries. The reason you can get away with this is the lithium packs are slightly higher voltage and can put out significantly higher current than lead-acid batteries. Short bursts of high current is what is needed for starting and what these lithium packs are ideal for.
Also if you do a lot of cold weather riding Lithium batteries are not for you. They can work but you have to "wake up" the battery. I'm not sure but I believe it's putting a load on a cold lithium battery heats up the battery by the resistance in the cell. Once warmed up the cell starts to work again.
Here is me trying to start my Vulcan 500 on a cold winter day with an 8 cell lithium iron phosphate pack (4s2p):
https://www.youtube.com/watch?v=oHSbL-cBUFMAnd a ridiculous extreme of trying to start it in -13F conditions:
https://www.youtube.com/watch?v=PPXG5_LQcYMI might have been able to eventually start it but I gave up when my bare fingers started to literally freeze.
Over the last almost year and a half I have not needed to do anything to the battery except for 2 weeks after I got it when I stoopidly turned the key to park (tail light on) instead of off and completely drained the battery. I figured the battery was toast but I jump started it from a car and drove 3 miles down the road to dinner. Much to my surprise that little distance was enough of a charge that I could start the bike after dinner. I rode home and charged it briefly with a standard lead acid charger to get some charge back into it. FYI you typically don't want to use a lead acid charger since it can easily over charge and ruin a lithium battery. I'm sure that little mistake shortened the battery's life but it's still cranking strong.
It's my understanding that the cells used in these batteries are the same used in power tools and tend to be much more tolerant of over charging/draining too low compared to other lithium batteries such as Lithium polymer (LiPO) often used in hobby RC applications. LiPO are very easy to destroy if over charged or drained too low.
I'm sure occasionally balancing cells will extend the batteries life but in my experience it isn't absolutely necessary.