Duracell Coppertop 9V Battery, Long Lasting Batteries, 4 Pack

I'm in my last few batteries but these lasted me a good four years. We use these for certain electronics and these last really long. One machine I use them for is a electric muscle massager which uses a lot of power and it's 60 minutes per session. One battery lasts me weeks with continuous use so that means their capacity is really high and they drain slowly. They also offer a guarantee that if you're not satisfied with the product you can call the number in the back and I assume they'll give you replacements. Although these packs can be expensive, it's one of those purchases you buy one time and you're set for years.