As long as we’re talking about jump starting cars, be sure to check how to jump start your particular car. Don’t just assume you can hook up battery to battery. Some cars should not be jumped by hooking up the batteries directly. Instead, there may be special posts under the hood that should be used when attaching jumper cables. I know some BMWs are like this. If you jump start a BMW from the battery, it may fry some of the computers (learned from personal experience). Instead, they have a special positive post under the hood that can be used with jumper cables.