This problem about Lenovo (various models) battery charge suddenly dropping from a moderate charge level (~40% in my case, ~20% in this thread, dropping to ~6% or 7%) has been plaguing me since acquiring 4 NEW batteries, two from a third party provider (returned) and two from Lenovo-Encompass.
I FINALLY SOLVED THE PROBLEM!. It is caused by the power manager in Lenovo Vantage. Now I am again getting 3 hours battery life instead of 1 hour, in my ThinkPad E560.
The successful solution depends on: 1) restoring the max. charge level to 100%, in Lenovo Vantage, instead of e.g. 95%; and 2) doing three steps to completely uninstall Lenovo Vantage. You should know how to do part #1 already.
Part 2, step #1: Uninstall Lenovo Vantage from Win10's Apps list (you won't find it under Programs).
Part 2, step #2: Using an administrator command prompt, execute this command (without quote marks):
Part 2, step #3: In Device Manager, expand the System devices category. Right-click System Interface Foundation V2 Device, and then choose Uninstall. (Step 2 should have removed it, but in my case didn't.)
A further note - I bought my E560 in late 2017. For many months I was regularly having blue-screen crashes, sometimes several times per day. Finally, uninstalling Lenovo's battery utility of that time (Power Manager) solved the problem once and for all. (And many others had had this exact same problem, and it continued over many updates to Power Manager.) It seems Lenovo still has not figured out how to do battery management right (so rely on Windows battery management instead!), and may even have carried the same buggy part of the code over into Lenovo Vantage.