Battery Keeps Going Flat
A battery that keeps going flat is old, not being charged enough, or something is draining it while the car is parked.
Normal risk
Not dangerous, but the car may not start. Have the battery and charging system tested.
Short answer · Why does my car battery keep dying?
The three usual causes are a worn battery, an alternator that does not charge properly, and a parasitic drain from something staying on after you lock the car. Short trips also never recharge the battery fully. A battery and charging test answers most of it quickly.
Safe checks you can do
- Measure battery voltageAbout 12.6 V when the car has stood a few hours is healthy.
- Check charging voltageWith the engine running, usually about 13.5–14.8 V.
- Look for lights left onBoot, glovebox or interior lights, and accessories.
Questions that narrow it down
- How old is the battery?Many last about four to six years.
- Mostly short trips?Not enough charging time.
- Any aftermarket accessories?Dashcams and trackers can drain the battery.
Possible causes
Listed without ranking. Use the questions above to see which ones fit your car.
- Worn batteryLost capacity.
- Alternator not chargingRegulator or belt.
- Parasitic drainModule or light staying on.
- Short tripsBattery never fully recharged.
Questions about Battery Keeps Going Flat
Can I find a drain myself?
With an ammeter, a workshop measures the current with the car locked and asleep, then pulls fuses one by one.
Does a new battery need registering?
On many modern cars, yes, so the charging system adapts to it.