Sold an old van to a guy this past spring that had been setting for close to 3 years without being started. The battery was dead and had been dead through at least 2 Michigan winters. He pulled one of those out of his pocket and I laughed at him. No way was he starting that van with a power pack that small. Two minutes later he was laughing at me as the van sat there running. That thing is a must have as far as I'm concerned.