Yes, you are correct. However, the Stratux works very well. I use mine with a battery attached to the bottom and sit it on the glare shield on a piece of rubbery shelf liner. I have a spare battery in my flight bag, but have never needed it. I keep the Stratux in my flight bag and recharge the battery after every flight when I get home. Of course, you can use a 12v plug if you don't want to use a battery.
It is a good option if you can't replace your Pingbuddy.