The most common roadside call we dispatch is a jump-start — somebody's vehicle won't crank in the morning, often after a cold night. The jump itself takes 5–15 minutes. The question that matters is what happens after.
Two failure modes look identical from the driver's seat: a one-time drain (interior light left on, short trip in cold weather, parasitic draw overnight) and a battery at the end of its life. The first is fixed by a single jump-start. The second will strand you again that night, or the next morning, or in a parking lot two days later.
Trained technicians don't guess. After the jump, they run a voltage check with the engine running. A healthy alternator pushes 13.8–14.5 volts at idle. Below 13, the alternator isn't keeping up or the battery is shot. They then load-test the battery itself. A battery that drops below 9.6 volts under load is failing.
If the test indicates a failing battery, you have two options: drive directly to an auto-parts store while the engine's running (don't shut it off), or replace the battery on-site. We carry Group 24, 35, 48, 65, and 78 batteries for most American and import vehicles.
Cold weather is the accelerator. Batteries lose about 35% of cranking amps at 32°F and 60% at 0°F. A battery 'fine' through fall can fail on the first freeze.