I will have soon an electric scooter with a 60v (top 67.2v) and 35ah battery pack. As it is designed, it can be charged by one charger which pumps 2,5 amps or it can be charged by 2 chargers in parallel, pumping 5A. That's ok for city use, it can charge over night, there is no problem waiting few hours for a full charge. But from time to time I plan to take trips into forest, between villages, etc. and I may need to charge it on my way, much faster, in an hour or so. For that I can purchase a 60V and adjustable 5-25A charger to take with me and plug it where I can find a wall plug, then continue my trip. But searching on aliexpress for similar sized battery packs, I discovered something strange in the specifications. For a 60v 20ah pack, the maximum continuous discharge current can be as high as 50 amps, but the charge current is max 5A. Why?? The connections between cells clearly can support high currents, otherwise it cannot discharge with 50A without damage. Why is the charging max so low and what happens if I push 25A with a powerful charger? Thank you.
Okay, let me offer this hand-waving explanation. After quick Google for [what limits charge rate for LiIon batteries?], several articles came up, like this one. In simplistic and very general therms of Physics, I would say that there is an asymmetry in solid-state chemical processes during charge and discharge. Essentially the charge is a process of some "order" in lithium ions deposition. So a higher temperature works against this process and slows the ordering down. The discharge process is sort-off "disordering", and goes more intensively with increase of temperature. The Joule heat, however, warms up the Li-Ion cell in both cases. So the charge must go slower to get the final state of charge, while release of energy is not limited. That's why the asymmetry exists between recommended charge and discharge process for batteries.