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Will my car battery die in cold weather?

car battery tips Haynes.com

Fact: car batteries are affected by cold weather. Although it’s relatively mild at the moment, winter will be in full flow soon and many of us are likely to see frost, hail, sleet and even some snow.

The wintery conditions place extra strain on your vehicle’s battery. With the headlights used more than usual, the heater blower motor running, heated seats doing their thing and the heated rear screen on, it’s a good idea to keep your battery in the best of health. 

The first thing you can do is remove any battery cover, then use a soft brush (the type that comes with a dustpan) to clear away any dirt or debris from the top of the battery, particularly around the battery terminal posts. A layer of rotting leaves or similar will retain moisture and could cause a current drain.

If the connections to the battery look corroded (shown below), carefully pour a little boiling water over the terminals and the corrosion should dissolve. Obviously, you need to be careful when doing this, so wear gloves and go slowly – only a small amount of water is required. 

Car battery terminal corosion

If the battery terminals and leads are very corroded, it may be necessary to disconnect them to physically remove the corrosion with a wire brush or abrasive paper. Usually, the negative lead must be disconnected first and reconnected last, but check with your Haynes manual for the correct procedure.

Be aware that some equipment, such as electric windows and the electric sunroof, may need to be reset once the battery is reconnected. Again, the Haynes manual will tell you if this is so.

Once any corrosion has been removed, check the security of the connections, and apply a thin layer of petroleum jelly (shown below). This should keep the connections watertight and prevent any more corrosion from forming.

Applying protection to car battery terminal

The days of removing the caps and checking the electrolyte level within the battery cells are long gone. Batteries are now ‘maintenance-free’; so as long as the casing isn’t cracked, the electrolyte level should be fine.

Most modern vehicles have a charging system that is more than capable of keeping the battery in a good state of charge in the winter, providing the alternator drive belt is in good condition and the alternator is working properly. Your manual will tell you how to check and, if necessary, renew the belt.

Keeping the battery in a good state of charge gives you confidence that on a cold, frosty morning, when the key is turned, the engine is going to start.

Find out how to check your battery’s health

I own a few vehicles, some of which don’t get used every day. So I tend to keep an intelligent battery charger connected to one in the garage, and plug a small solar charger into the diagnostic socket of the one parked outside. One of the pins of the socket connects directly to the battery and one to earth. So the solar panel sits on the dashboard, and trickles charge through the socket and into the battery. 

If a turn of the key produces the dreaded ‘click’ or turns the engine over really slowly, the chances are that the battery has lost its charge and is flat.

Years ago, I would have tried to bump-start it, with an assistant giving the car a push. However, with the introduction of catalytic converters in the ’90s, this is no longer recommended. Any unburnt fuel going through the engine into the exhaust system could damage the converter and cause a hefty bill.

How to start a flat-battery car

There are only three realistic options available:

1 Jump-start using another vehicle and suitable jump leads

With your neighbour's car running at a fast idle, and parked alongside yours, connect the jump leads to your battery, positive-to-positive and negative-to-negative. Turn the key and start your engine!

It sounds simple, but there are a few things to bear in mind:

  • If the donor car's battery is a lot smaller than yours, it will struggle to provide enough power. For example, a Fiat Panda is going to struggle to help a Range Rover.
  • Poor-quality jump leads may overheat and may not be able to transfer sufficient electrical energy. Small-diameter cables will heat up fast trying to carry the battery power, and as the temperature increases, their capacity decreases.
  • Make sure the cars aren’t touching.
     
Jump leads car battery

2 Use a jump pack

A jump or booster pack contains a lithium battery which should be kept charged in case of emergency. The lithium technology means the jump pack should remain charged for a long time – keep it in your glove box.

Considering the small size and weight of the unit, they really pack a lot of punch, and can usually start almost any size engine. Simply connect the jump pack leads to your battery as per the instructions provided, and start your engine. 

Priced from about £60, these efficient little units are fast becoming essential winter must-haves.
 

Car battery jump pack

3 Buy a new car battery

Jump starting or using a jump pack will only work if your battery is partially discharged. If it's completely discharged, the chances are it has an internal fault, and no amount of additional electrical energy will get the engine going. Replacement is the only option.

Batteries have a finite life. Even the best batteries are only guaranteed for a maximum of five years, and although they can last much longer than this, the cheaper ones can often fail after two or three years of use. How much does a car battery cost? They're not cheap – a bill north of £150 and even beyond £200 is possible.

Maybe it’s my imagination, but years ago batteries used to gradually deteriorate, giving plenty of warning that they were going to fail. Whereas these days, they can often fail completely with no warning whatsoever. It’s happened to me twice in the last 12 months. You have been warned!
 

Car battery