If you didn’t want to accept the charge tolerance why did you buy it?
Where did you buy your Xtar MP1S from?
I like to be closer to 4.20v myself. I understand tho that my preference does not change the accepted tolerance.
If you can solder buy a few $1 tp4056 CC/CV li-ion charger boards. Ebay search. HKJ review. Give away ones that aren’t close enough to 4.20v for you. You could even put the tp4056 board into the shell of a Xtar MP1S or other charger.
Because none of my other chargers (including XTAR ones with the same specification) overcharges. Seems MP1S is cheaper made with lots of lemons produced. I bought it from XTAR.
I can solder but I don’t want to build chargers for a hobby… Also the version with LED output cost more and require more work.
All of the tp4056 boards have charging & charge complete indicator leds. Either red & green or red & blue leds.
None of the companies that sell li-ion chargers actually manufacture the controller chips. Check the datasheet for any of the commonly used li-ion charger chips. Most have a charge tolerance of 1% or +/-0.05v. Xtar MP-1 seems to use dual SE9017 or TP4057, haven’t found a teardown of MP1S.