battery replacement

My Lenovo Vibe K5 note battery needs to be replaced. When battery life is reduced, it is supposed to reduce charge at a faster rate right, but what happens is the phone suddenly gets switched off and doesn't switch on unless I start charging. When I charge phone when it is on, the battery goes...

I have a Moto G4 bought in 2017 January. It's battery was replaced with a compatible one 2 months ago as the original battery wasn't holding charge. Since then the phone often suddenly switches off even before battery level goes to 0 & when the charger is plugged the battery level is not 0 (it...

I want a (genuine) battery replacement for my Lenovo Thinkpad T61. I narrowed down some results (1, 2, and 3) from eBay. But they all have different mAh values. Is it okay if they are different from the one on my current battery? Also, suggest some points I need to look out for when buying the...