My lady has the small jumper cables in her car. Last year, we had a cold night, and her battery did not have enough juice to start the car the next morning. The little cables worked just fine. Maybe if her battery had been completely dead, they might not have worked as well. Don't know.

BTW, a trick I learned from an OLD tow truck driver is to connect the cables and then wait a couple of minutes. He also taught me to be the only one to connect both ends, so that I know for certain that red is positive and black is negative. Also, get behind something before trying to start the dead car. I saw a car battery vent once while jump starting, spraying battery acid within about a 5-foot radius.