As said earlier in this thread if you want to run a rechargeable lithium batteries you need a lipo battery alarm plugged in to tell you when the voltage is getting too low as this hurts the batteries, you also need an expensive balance charger. Not really a cheap endeavor just to have a faster train.
Lithium rechargeable batteries are also a fire risk, just look at how many hoverboards have gone up in smoke due to incorrect charging and cheap lipo batteries
Lithium rechargeable batteries are also a fire risk, just look at how many hoverboards have gone up in smoke due to incorrect charging and cheap lipo batteries