A car that starts fine in the evening and is flat by morning almost always has one of three problems: an old battery, something drawing power while parked, or a charging fault.
What usually causes it
- Old battery. Heat is hard on batteries. Many only last a few years here, and a weak one cannot hold charge overnight.
- Parasitic drain. A stuck relay, a boot or glovebox light that stays on, a faulty alarm or an aftermarket stereo or dashcam wired badly can all drain power.
- Alternator not charging. If the battery is not topped up while you drive, it will flatten even if it is healthy.
- Loose or corroded terminals. A poor connection stops charging and can also cause hard starts.
Signs to watch
- Slow cranking in the morning.
- Interior lights or dashboard dim when you start.
- A battery warning light while driving.
- White or green crust around the terminals.
What to do
A jump start will get you going, but it does not find the cause. Have the battery tested, the alternator output checked and the car scanned for a drain. Fixing the cause means you will not be stuck again next week.