Don't be @dave.

Whenever we sell a portable power bank battery-type thing, some size fetishists in the audience always pipe up to let the world know how stupid the deal is because you can get a battery with way more mAh for not that much more money. This story is for them.

You guys know @dave, right? Our head of creative & community? One hot day many years ago, a friend of ours was graduating from college. Dave and some other friends stopped on the way to the graduation to pick up something to drink. Dave was about to pay $1.09 for a 20-ounce bottle of soda… until he noticed that 2-liters of soda were on sale for 89 cents.

Dave could not bring himself to spend 20 cents more for much less soda. So he bought the 2-liter. In strict price-per-ounce terms, it was the right call. But in this context, price-per-ounce was the wrong metric. He had to lug around this big plastic jug of Mountain Dew all through the graduation, as if that were a perfectly normal, non-insane thing to do. Now, 20 years later, in group photos of the big day where everybody’s dressed up all nice, there’s Dave clutching his big green bargain bottle.

So it is with batteries. Price-per-mAh is the wrong metric. Follow it too far and you wind up hauling a backpack-sized battery everywhere. Dave’s fatal flaw was ignoring the balance between size and capacity in his single-minded pursuit of cheaper ounces of soda. That balance is illustrated in this super-scientific graph:

This Sunbeam 7800 mAh portable battery lies around the intersection of Prodigious size and More capacity. Yes, you can find bigger ones with a lower price-per-mAh. That should literally go without saying. But as we said, they’re going to be bigger. If you want a power bank about the size of your smartphone (slightly smaller, but thicker), here it is. If you want a bigger one with more power, go buy that instead.

It’s normal to want more for your money. It’s not normal to be such a fanatic about it that your power bank is the heaviest thing in your backpack, or that you carry a 2-liter of Mountain Dew around a semi-formal event. And no amount of explanation, of strict price calculation, will make it socially acceptable. Just ask Dave.