hope 21700 package coming soon as 40% more power than 18650 so great option for solar powerwall or eBike battery!
Have 60V lead acid Motorino which supplement with under seat 16Ah 18650 lithium into charge port using ON/OFF switch,
last test started ride with 64V lead and 68V lithium turn on thus adding lithium to battery pool drawing 14A from lithium
so goes up hill better and on return both lead and lithium 63V!
Then turn off and unplug lithium charging with solar panel and big advantage other than range of this config is
lead acid useful life extended as need less charges since likely never fall below 62V