Have both of what you mentioned (Sonicare). Our daughter gifted us with Sonicare Diamond toothbrushes a few years ago and mine started failing recently. I did not want to go buy a brand new one so my husband decided to try to fix it himself. He ordered a battery off
Amazon and took the toothbrush apart and put in the new battery. A bit more complicated than just switching out a regular battery but so far, so good. Seems to be working again but it does not show the light when charging. We will see how it goes.
I recently bought the battery operated Sonicare toothbrushes at Kohl's when they were on sale recently for $20. I will now bring those for travel instead of our regular ones which are on the heavy side.
We have found a huge difference since starting with the Sonicare toothbrushes. Even our dentist mentioned our teeth were better with less plaque.