Has My Car Battery Died?

Your car battery is the heart of your vehicle, so it seems apt that when it goes flat, we often say that it has “died”. It’s important that you know a little about how car batteries work, and the most common signs that your car battery needs to be replaced.

Car batteries are usually wet-cell batteries. This means that they contain a mixture of sulphuric acid and lead, and that there are two terminals coming out of the battery that allow the power to flow. Car batteries recharge slowly as you drive, but they will eventually lose their charge – especially if you spend a lot of time driving slowly and over relatively short distances. A flat battery will need recharged and you can do this with a domestic charger. As batteries get older, they stop holding their charge for as long, and they become more difficult to recharge. Eventually, it becomes time to replace them.

Why has my car battery died?

Car batteries can die for any number of reasons. Sometimes it’s a simple case of them being used for prolonged periods – perhaps you left your headlights on overnight, or you have a ‘parasitic draw’ from the radio, or even from a loose wire that’s touching something it shouldn’t be. Alternatively, the battery might have just lost some power because it’s old, or because it’s been damaged. Even rapid charging can actually warp the battery plates and make your battery less reliable.

Why do car batteries die in the cold?

Car batteries seem to die more quickly in the winter, but it’s not so much that they “die”, as that it’s hard to start a car when it’s cold. Gas is harder to vaporize, and the oil is thicker. In addition, batteries only put out half of their normal power at freezing temperatures. So if the battery isn’t operating at full capacity, it’s going to seem ‘dead’.

Usually, when the weather warms up, the battery should start performing like normal again. If it doesn’t, and recharging doesn’t help, then it’s time to replace the battery.

Why do car batteries die on concrete?

There’s a common myth that if you leave a car battery on concrete, the energy will leak out. This is just a myth. Leaving a modern car battery on a concrete floor won’t do any harm. This myth does have some basis in truth, though. The very first lead-acid batteries were made of glass cells that sat inside a tar-lined wooden box. If you left these on a damp concrete floor, then the wood would swell, and that could make the glass break.

Modern batteries have hard plastic cells, so a bit of dampness won’t do them any harm. In fact, concrete is a good surface to put the batteries on, because the concrete acts as a thermal buffer, preventing the battery from being damaged by extremes of temperature. If the lower cells in the battery were very cold (because the floor is cold), but the other cells were exposed to very hot air, then this could make the battery electrolytes stratify, and cause sulfation damage.

Overall, though, batteries are surprisingly resilient. So you don’t need to worry about them losing power if you keep them in a cool garage.

Why do car batteries die suddenly?

Really, car batteries can die at any time of the year. Cold weather appears to cause more battery failures because of the reduced power output, the reduced ability to accept charge, and the load increase from heaters, windscreen wipers, etc, but there are many other reasons a battery could die.

Batteries are only designed to last a few years. If your battery is five years old then it’s likely to be on its last legs and you should replace it if you find that you have trouble starting your car. The frequency with which you recharge it matters as well. If you aren’t doing frequent journeys of a decent length then the battery won’t get recharged as often as it should.

Another thing that matters is the load that the battery is exposed to. If you’re using lights and entertainment systems, heaters, and other appliances in the car a lot then this is going to affect it.

A lot of the time, the battery isn’t really dying suddenly. A car battery will give you warning signs before it dies, usually, such as:

  • A different sound coming from the engine when you try to start it
  • Having to try a couple of times to get the engine running from a cold start
  • The headlights will appear slightly dimmer

These are all signs that there’s something wrong, and that you should look at recharging the battery, or replacing it.

Why do car batteries die when not used?

Car batteries slowly lose charge when they are not used. Some energy leaks out of the contacts, especially if they are dirty and calcified. In addition, the battery acid can start to stratify, making it able to hold less energy.

There is often a small amount of draw of energy from the battery when it is in the car, even if you aren’t driving. Some appliances pull a tiny amount of standby power. Sometimes there could be a loose wire that is pulling power too, and that power is literally just running ‘to ground’. Or, worse, damaging something else in your car.

You can fit battery conditioners and intelligent chargers to your car, which will monitor the battery and make sure that it is kept at an optimal charge level. These will greatly prolong the life of your battery.

If you notice warning signs that your battery is failing and you need to prolong its life, try turning off everything electrical that you can when you start your car, and dip the clutch slightly too – this will reduce the load on the battery so you can get a few extra starts out of it. Replace the battery at the first opportunity.

Also see