IF lithium batteries take a special charger for when its off the bike, how can the charging system in the bike, made for a lead acid battery, be OK ?
Just doesnt make sense to me.
Point of information. The lithium batteries used in marine and automotive applications use a different chemistry (LiFePO4) from the ones in our phones, laptops, power tools, etc. Never try to charge a "12V" lithium battery from a laptop with an automotive charger.
Here is info from Battle Born Batteries - they supply 100AH 12V LiFePO4 batteries for marine use. ($800 each!)
Note they are talking about a charger that can be set for different battery chemistries, including AGM type lead acid batteries. Many modern bikes, including ours, use AGM batteries. AGM has slightly different charging specs and are more costly than the old wet cell lead acid batteries.
In another place they mention that a dedicated Lithium charger will charge the battery much faster (a big issue in some marine usage) but I don't see that as a problem for motorcycles.
Battle Born batteries FAQ
How can I charge a LiFePO4 battery?
There are some chargers and controllers that are programmable to ensure full usage out of your battery, but most will have an AGM setting which normally bulk charges about 14.4 volts and float at 13.6 volts. These levels are great for your Battle Born battery.
Cold temperature charging
A YouTube Tesla Model 3 owner did a test where he left his car outdoors for 48 hours of bitter cold, parked near a Tesla SuperCharger. He found it took 45 minutes after he connected the charging cable before the charging rate rose from a very low level. He (and I) assume the car used this time to warm the battery up (to perhaps 32F degrees).
Our bikes do not have this charging protection built in so beware if you want to ride a bike with a Lithium battery colder than 32F. I have no idea how to measure the internal temperature of our battery