Car battery keeps going flat: causes and solutions

A battery that goes flat once is annoying. A battery that keeps going flat has a cause. Below you can read what the causes are, what you can check yourself and when you had better stop driving.

By the team at Autobedrijf Willemsbrug, RDW-approved APK (MOT) test station since 1979 · Updated 6 November 2026

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The short answer

A car battery keeps going flat because of short journeys, cold weather, standing still for a long time, a worn battery, an alternator that does not charge properly or something that keeps drawing power while the car is off. According to the ANWB, the Dutch motoring organisation, a battery lasts three to six years, and it goes flat if the car only makes short trips or stands still for a long time. Recharging does not solve the problem if the cause remains. So have the battery, the charging system and the starter motor tested, so you know whether you need a new battery or whether something else is wrong.

Battery service at Autobedrijf Willemsbrug: we test the battery, the charging system and the starter motor first, and only replace what is needed. A new battery suits your car (AGM or EFB with start-stop) and we register it with the on-board computer if your car requires that. We tell you the price in advance based on your registration number. Call +31 10 479 00 00. You bring the car and we call you when it is ready. A loan bike is free while one is available. Saturdays too. Our team speaks English. More about our battery service

Why does my car battery keep dying? The six causes

The battery supplies the power to start the engine, and the alternator recharges it while you drive. If it keeps going flat, more power is going out than coming in, or the battery no longer holds its charge. In our workshop we see these six causes:

Cause What you notice What helps
Short journeys The car starts with difficulty after a week of only short trips A longer drive now and then, or topping up with a battery charger
Cold The problems start in autumn and get worse in frosty weather Having a weak battery tested before winter
Standing still for a long time The battery is flat after a holiday or after a few weeks of not driving Topping up, or connecting a battery charger while the car stands still
Worn battery After charging, the car starts well for a while and then badly again Testing the battery and replacing it if needed
Alternator not charging properly Red battery warning light while driving, dim lights, slow wipers Having the charging system and the alternator tested
Power drain while parked The battery is flat after a few days parked, even a new battery Having the cause of the drain found

Sources: ANWB (battery, battery problems, alternator) and ADAC. More than one cause at the same time is possible.

The ANWB writes that a battery can go flat if the car only makes short trips or stands still for a long time, because it does not get the chance to charge fully. According to the ANWB, cold weather puts more strain on a battery. The ADAC, the German motoring organisation, adds that a battery takes up charge less well in frosty weather. And modern cars have many ‘sleeping’ systems that stay active in the background, even when the car is off.

Dirty battery terminals can also play a part. According to the ADAC, dirty terminals can cause leakage currents, which make the battery go flat faster.

Is the battery flat or worn out?

A flat battery can work well again after charging. A worn battery cannot. According to the ANWB, a battery lasts around three to six years, sometimes longer. The ADAC gives an average of about five years. If your battery is older and keeps going flat, wear is a likely suspect.

The resting voltage tells you something about the charge. You measure it with a voltmeter on the terminals, after the car has stood still for a few hours. For a standard lead-acid battery, the ADAC gives these values:

Resting voltage Charge according to the ADAC
about 12.6 volts about 90 per cent
about 12.4 volts about 70 per cent
about 12.2 volts about 50 per cent

Source: ADAC, Autobatterie testen (23 March 2026). An AGM battery gives slightly higher values.

A good voltage does not mean the battery is healthy. According to the ADAC, charging does not show you what condition the battery is in. For that you need a battery tester. It puts a short load on the battery and shows how much starting power and condition are left.

How do I know if the alternator is not charging the battery?

A red battery warning light while you drive is the clearest sign. According to the ANWB, a red battery light while driving, dim lights or wipers that move more slowly point to a problem with the alternator. The alternator supplies power and recharges the battery. If it does not charge, the car runs on the battery until it is flat.

A new battery then only helps for a short time. It will also go flat if the alternator does not charge. According to the ANWB, an alternator lasts at least 6 years or 100,000 km with normal use. You can read more about this warning light on our page battery warning light on: alternator testing and repair.

What can you check yourself?

Start with the easy things. Something is often left on without you seeing it.

  1. Lights and doors: check whether the interior light, the boot light or the glovebox light goes off when everything is closed.
  2. Connected devices: unplug chargers, a cool box or other devices from the 12V socket when the car is parked. According to the ANWB, the battery goes flat very quickly if a lot of power consumers are on while the engine is not running.
  3. Driving pattern: if you mainly make short trips, plan a longer drive now and then.
  4. Topping up: if you do not drive much, use a battery charger. According to the ANWB, a few hours of charging a week is usually enough. Connect the red cable to the positive terminal first and then the black cable to the negative terminal.
  5. Battery terminals: are the terminals tight and clean? White or green powder on the terminals is a sign of corrosion.

Does the battery still keep going flat after that, or is it already a few years old? Then have the battery and the charging system tested before you buy a new battery.

Can I still drive if the battery keeps going flat?

Yes, as long as the car starts and no red battery light is on. But use this rule of thumb:

  • The car starts, with or without a jump start, and no warning light is on: you can drive. Drive a good distance so the battery recharges, and have it tested soon. Do not leave the car parked for a long period.
  • The red battery light comes on while you drive: do not drive on. According to the ANWB, you must stop and pull over when a warning light is red. The alternator is then probably not charging and the car may break down on the road.
  • The car will not start: have it brought in. According to the ANWB, a jump start on a modern car can damage the electronics if it is not done correctly. If in doubt, call the ANWB Wegenwacht (the ANWB’s roadside assistance service) or your breakdown service.
Car will not start? Your breakdown service, the Wegenwacht or a recovery company can bring it to us. Outside our opening hours that is possible at your own risk: park the car in front of the garage and put the key through the letterbox. A car that will not start goes into our schedule as soon as possible. Read more on our page car won’t start.

How we find out why the battery keeps going flat

We find out why the battery goes flat and only replace what is needed. A new battery without knowing the cause will only leave you with another flat battery later. We start with these steps:

  1. Battery test: with a battery tester we measure the charge, the starting power and the condition of the battery.
  2. Charging system test: we check whether the alternator charges the battery properly.
  3. Starter motor test: a starter motor that runs heavily demands a lot from the battery.
  4. Diagnostics and inspection: we read out the car and look at the terminals, the cables and any equipment that was fitted later.

We then tell you what we found and what the solution costs. That price is one amount based on your registration number (kenteken), and we only carry out repairs with your approval. If the alternator or the starter motor is the cause, we test and replace it in our own workshop. You can read more about starter motor replacement and car battery testing in Rotterdam on our service pages.

Frequently asked questions

Is my battery broken if it keeps going flat?

No, that is not necessarily the case. A battery can keep going flat because of short journeys, standing still for a long time or an alternator that does not charge properly. A battery tester shows whether the battery itself is worn out.

Can a new battery also keep going flat?

Yes. If the old battery was not the cause, the new one will go flat too. Think of an alternator that does not charge properly, something that keeps drawing power, or a lot of short journeys. So first have the cause found before you fit a new battery.

How long can a car stand still before the battery is flat?

That differs per car and per battery. According to the ANWB, a battery can go flat if the car stands still for a long time, especially on modern cars with many systems that stay active in the background. According to the ANWB, in a hybrid this fairly often happens after two to three weeks of standing still.

Does it help to disconnect the battery?

Yes. It stops the car from using power. But according to the ANWB, a disconnected battery also goes flat eventually. On modern cars, settings can be lost when you disconnect the battery. So check the owner’s manual first.

Will the battery recharge if I go for a drive?

Yes. The alternator charges the battery while you drive. According to the ANWB, after short trips that is often not enough to charge the battery fully. If you do not drive much, a battery charger is a good addition.

What is a good voltage for a car battery?

According to the ADAC, a resting voltage of about 12.6 volts means an almost full battery, and 12.4 volts about 70 per cent. Only measure once the car has stood still for a few hours. The voltage says nothing about the condition of the battery.

Will you come out to start my car?

No. We are not a breakdown service and we do not give jump starts at your home. The Wegenwacht, your breakdown service or a recovery company can bring the car to us. A car that will not start goes into our schedule as soon as possible.

Does your battery keep going flat?

Call +31 10 479 00 00 with your registration number. We find out why the battery goes flat and we tell you the cost in advance.

You will find us at Boterdiep 11 in Rotterdam-IJsselmonde, close to Stadion Feijenoord (De Kuip). We work by appointment. For a quick question or check you can walk in without an appointment.

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