Six months ago, the battery in my 2010 Mazda 3’s key fob (aka “flip-key”) totally died and I needed to replace it. The battery in these things is a CR1620, which I couldn’t find anywhere in stores, so I ordered the cheapest ones I could find off eBay — a pack of 3 generic brand Eunicell (made in China) for $2.18 CAD shipped. Unfortunately, I didn’t have a good first experience with them. There’s an orange LED that should light up whenever you press a button on the key fob. On a working key fob that still contained the original Panasonic battery from the manufacturer, the LED was bright and solid, but on the one I had just replaced, it was flickering and dim. I actually couldn’t get the first battery to work, so I had to take a 2nd one from the 3-pack, and that eventually did work, but never 100% reliably. I also had to reprogram the key fob to be recognized by my car. I concluded that these batteries were just “weak” or underpowered, or that the eBay seller was giving me old/used stock (
I now realize that this wasn’t true. EDIT: it turns out my original suspicions were probably correct; see update below!). Anyway, a week ago, I sought out a brand name and ordered a 5-pack of Sony batteries (made in Japan) from Amazon, which cost me $13 all in (including Ontario taxes).