TL;DR - Loses its charge in the glove box, requires a functioning car battery to charge.
I bought this unit because my three-year-old thinks it's fun to turn on the dome lights in the back of my car, which I don't notice until the next day, when my battery is dead. That happened this morning. I thought, "no problem! I bought this cool jump starter that fits in my glove box!" Pulled it out. Checked the charge: 51%. First problem with the unit: why can't it keep a charge for a month? Two months, even? Other power supplies can do that. Am I supposed to keep it plugged in all the time? Its half-dead battery alone would have only warranted a two-star rating, but it gets even dumber.
So fine, I'll go inside, charge the unit, wait a bit and then go try again. But what's this? There's no way to plug this in to charge, EXCEPT IN A CAR. Yes, the only provided way to charge this unit, to jump start your dead car battery, is with a car battery! [Facepalm]. Thankfully, I randomly had a plug in that drawer at home that worked, but otherwise I would have had to walk to the store to buy one.
So thankfully, I had this review to write while I sit and wait for the thing to charge so I can try again.