• mattimwm

Why do batteries fail in the cold?

Let’s set the scene. It’s freezing out, maybe it's snowing. You’re in a rush to get somewhere and you want to be in the cold for as little as possible. You slip down the drive and unlock the door, you get in to see iced over windows and you think “Brrr, lets blast that heater”. Problem is, you stick your key in and turn it… and nothing happens. Here’s why batteries fail in the cold, and the steps you can take to prevent it.

Most batteries these days hold their charge by what’s called a “liquid electrolyte solution” - this a mix of chemicals inside the battery that clings on to the electricity, and this solution is affected by temperature. They are capable of freezing, but this requires unusually low temperatures. General cold conditions however, such as the winter months, can reduce the solutions abilities to keep hold of and transfer the needed power. This is why it's more likely that your battery will struggle during the winter.

It’s not just the temperature though - how you’re using your car can have an impact on the battery’s performance. So with the winter months, there’s more rain or snow, days are shorter and we’re using our lights, our heaters and our windscreen wipers more often. All of this contributes to the strain that’s on your battery. This in addition to how cars are used less during icy weather and over the Christmas holiday period when many are off work is a recipe for low batteries, because they gradually lose their charge when they aren’t being used.

Diagnosing a dud.

So, how do you know if your car has a flat battery? If you don’t hear anything when you turn the ignition key, or you notice a faint whining noise but the starter motor doesn’t kick in, the chances are you have a flat battery. There are other warning signs too. For example, the ignition lights on your dashboard may not come on, or you might not be able to unlock your vehicle via remote central locking.

Similar effects from different problems do exist though. A faulty alternator or starter motor will mean you car won’t start or your battery won’t charge properly. Sometimes a dead battery, isn’t a dead battery. If your alternator has failed or is in the process of failing, you might notice dashboard lights flickering, it might make a loud noise while the car is running or if you have a relatively new battery that keeps going flat, chances are your alternator isn’t working. For the starter motor issue, if you turn your key and there’s a clicking sound instead of the car turning over, or no sound at all but your lights and heater work, that’s probably your starter motor.

If you can’t tell what the issue is, give us a call and we’ll try to diagnose it over the phone. If we can’t then we can arrange a time convenient for everyone where we can get to your car and have a look at it wherever it stopped cooperating.

So how do you fix a flat?

Flat batteries always seem to happen at the worst of times. If you’re in a rush, you could try jump starting the car. For this you’ll need a friend, a friend’s car and some jumper cables.

Here’s how:

- Park your friends car with its bonnet as close to yours as you can get. Opposite your car is perfect, or right next to your car might work too.

- Turn off both cars, pop the bonnets.

- Connect the red cable to the positive terminal of your car, then the positive terminal on your friend’s car.

- Connect the black cable to the negative side of your friend’s car, then to a grounded part of your car - a solid metal part of the engine will be fine.

- Turn on your friends car and let it run for a few minutes.

- Turn on your car. You may have to add some rev’s to the healthy car while you try starting your own car.

After you’ve jump started your car, you’ll want to drive it for around half an hour to try and get some charge back into the battery. You can also recharge it using a Car Battery Charger. A trickle charger will be kinder to your battery, but will take longer.

If you want to get your battery’s health checked, bring it down to us and we can assess how strong the charge is in your battery. If you’re driving it regularly and it doesn’t hold enough charge, chances are it’s on its way out or your alternator might not be working at 100%.

There are a few ways to keep your battery in good health. For example, if you’ve got a garage, put your car in there when the weather gets cold to insulate it from the temperatures outside.

Another way is to switch everything off before you switch your car off, this includes lights, radios, sat navs, heaters, anything that will drain your battery or put a bigger strain on it when you try starting your engine.

If you have a multimeter, you can check the voltage of your battery. Make sure you leave your car for at least a few hours after driving to check this, as you need to get the “resting voltage”. Tes the battery by connecting the red probe to positive terminal of your battery, marked with a +. Connect the black probe to the negative terminal, marked with a -. The read out should be no less than 12.6V. 12.2V indicates a 50% charge, and anything under 12v is classed as discharged, time for a new one! (if it’s coming up as a negative, for example -12.6v, then you’ve got the probes the wrong way around!)

If you don’t have a multimeter though, pop down to the garage if your car still starts and we’ll check the voltage for you. Reliability on car batteries falls quickly after about 3 years as the chemicals inside become less cooperative. If your battery is close to or over 3 years, it’s probably best to buy a new battery anyway.

Stay safe this winter, if you have any concerns then book a visit in, or drop by:

Brendon Garage

Windsor Street

Haverton Hill


TS23 4EY

01642 564120

Special thanks to Matti from MWM Digital for helping us with the blog!

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