A battery's performance abruptly drops just before it fails to start a vehicle. Before that abrupt drop, the battery may still start the vehicle, but its performance has begun to decline. It is said to be marginal. Extreme heat or cold, or any sort of unusual demand, can cause the battery to fail. To enhance accuracy and functionality, the ED-18 incorporates refinements such as temperature measurement, battery age information and a local climate database based on the shop's zip code.