Re: New battery for samsung galaxy s5
1) The way to be more sure that the battery won't explode (or, more likely, "vent fire") is by the manufacturer. Cheap batteries, sold by unknown companies, are more likely to be rejects and more likely to have problems. (Although it's not a guarantee - Sony had a huge lot of lithium batteries vent fire once.)
2) If you're looking for more than 2800mAh (the standard battery), you have to look to 3rd party sellers. The Samsung battery is 2800mAh. ZeroLemon has a good reputation, and they have an 8500mAh battery for about $60. ($6.35 for a battery - any lithium battery - should throw up warning flags. It's like $1,000 for a new car. $10-$12 for a battery for an older phone - if you're ready to condition it - could be a good battery.) Take a look at
Amazon.com: [180 Days Warranty] ZeroLemon Samsung Galaxy S5 8500mAh Extended Battery + NFC + Rugged Black Zero Shock Hybrid Protection Case, Includes Free High Quality Screen Protector - World's Highest S5 Capacity Battery with World's Only U
I'm not recommending them, I've never used one of their batteries, but I've read a lot of happy posts about them on a lot of forums.
I just keep a fully charged spare stock battery in a soft plastic case in my pocket and switch them if the one in the phone gets below 40% and I still need to use the phone before I can charge it. And I switch them every month anyway.