We carry a Mighty Jump by Viatek in our car under the passenger seat to use if we ever need to. It was the best $24 insurance and even with our roadside service. Here is the link if you want to look at it.
Mighty Jump Emergency Jump-Starter
Saves having to have another car or a service call. It will not work on a defective battery, but will provide a jump for a dead one.
LW888