This is an item I can't believe I didn't own before now!
This is especially handy if you have one of those little, battery eating mirrorless cameras.
One of the nicest things about this charger is you can buy the plates based on which battery you are charging. So you can get 2 plates for your Sony A7R batteries, or 2 plates for your A77ii batteries, or you could charge one A7R battery and one A77ii battery at the same time.
It also has a USB charging port, the ability to use a 12V car adapter and a digital display that shows you the voltage and percentage charged of each battery. You can also get plates for all types of cameras, so it's not limited to Sony batteries. The possibilities are endless really. Here's the list of plates they currently offer.
For the record, I have no affiliation with this company. It's just a product that I find extremely useful and thought you might, too.