ISDT C4 EVO problem – unstable charging voltage

Batteries and Chargers Chargers
1

Long story short. Recently I bought ISDT C4 EVO for my travel needs and was really happy with it, until I tried to charge some protected 18650 Panasonics. In 2 out of 3 cases charging was terminated by battery protection circuit (batteries left at arround 4.1V). After playing a little bit around I found out, that charger has some voltage stabilization problems:

https://youtu.be/1Ny7qfO0vP4

During the charging and even without any load voltage jumps up and down. When charging Lithium batteries, occasionally exceeding 5V. Highest I saw was 5.1V.

My question is – how bad it is for the batteries (both Lithium and NiMh occasional voltage jump by around 1V over normal charging condition?

I got it on AliExpress, so returning is not a viable option (I’m stuck with it).

Charging termination seems Ok: Lithium batteries were at around 4.20V, NiMh – 1.45V

2

Whoa. That’s… weird. Never saw anything like that before.

It might be some weird test to see the cell’s response to a “voltage spike”, or may just be glitchy.

If it terminates at 4.1V, I might tolerate it, but keep charging only the same cells in case there is anything weird happening to them. This way you’d only toss 1-2 instead of a dozen.