Car Batteries and Cold Weather: Getting Ready for a Fraser Valley Cold Snap

A battery can start the car without complaint through a wet Fraser Valley fall and still fail on the first hard-frozen morning. Cold usually exposes a weakness that was already there. A battery that has been losing strength for months runs out of reserve the first time a cold engine needs more current than it can supply. To avoid that morning, have the battery and charging system tested in October or November, and replace the battery only if the test shows it's needed.

Why cold is hard on a battery

Two things happen at once when the temperature drops.

• The battery has less to give. The chemical reaction that produces current slows down in the cold. BCAA says a battery loses about 35% of its strength at 0°C, and CAA Niagara, citing CAA's Automotive Research Centre, puts the loss at about 60% once the temperature drops to -18°C.
• The engine needs more. Cold, thick oil makes an engine harder to turn over. CAA Niagara says a cold engine can need up to twice the current it needs in normal weather.

Winter also adds electrical load once you're moving. Natural Resources Canada lists heating, defrosting, headlights, interior lights, heated seats, heated mirrors and the washer pump as reasons a vehicle's electrical demand runs higher in cold weather. While the engine runs, the alternator carries most of that load, which leaves less to top the battery back up, especially at idle and on short trips. A healthy battery copes; a weak or partly charged one may not.

Short trips keep a battery undercharged

BCAA explains that idling alone won't fully recharge a battery: at idle, a modern charging system gives only enough to keep up with the vehicle's accessories, and getting back to a full charge takes a real drive. Its advice is to drive every three to four days, until the temperature gauge reads about halfway. CAA-Quebec makes the same point about summer driving: short, repeated trips prevent a full recharge. A winter of short, cold trips with the heater, lights and defroster all running can leave a battery undercharged right when a cold snap arrives.

Why summer heat shows up in winter

Summer heat wears a battery out faster than cold does. CAA-Quebec says heat can speed up battery wear, sometimes up to three times faster than cold weather, and BCAA says batteries fail far more often in hot weather than cold, pointing to the hot summers BC has had in recent years.

The damage can take months to show. A battery can lose capacity over a hot summer, still have enough to start a warm engine in September, and run out of margin the first morning it has to crank a cold one. BCAA reports spikes in battery-related roadside calls in both very cold and very hot months.

What a Fraser Valley winter means for your battery

Chilliwack winters are mostly wet rather than frozen, and the hard cold tends to arrive with Arctic outflow. In December 2022, for example, Environment and Climate Change Canada issued an Arctic outflow warning for the Fraser Valley, including Chilliwack (Daily Hive). Once that cold air settles in, it can linger: a forecaster quoted in the same story described the Fraser Valley as holding onto Arctic air longer than most places.

For a marginal battery, that pattern can mean little warning. It may get through weeks of mild, rainy weather and then face a run of frozen mornings all at once. Test it in the fall, before the outflow arrives.

How long does a car battery last?

BCAA puts average battery life at three to five years and notes that driving habits and extreme temperatures can shorten it. CAA North & East Ontario says the growing electrical demand in newer vehicles pulls that closer to three years. CAA-Quebec recommends having the electrical system checked by a professional once a battery is more than three years old.

BCAA suggests checking the manufacturing date on the sticker on the battery itself. If you don't know how old yours is, or it's past three years, that alone is a good reason to test it this fall. Any of these warning signs, drawn from the BCAA and CAA North & East Ontario lists, is also a reason to have it tested:

• A slow or lagging crank when you start the engine
• Headlights or interior lights that look dim or yellowish
• A horn that sounds weak or strange
• Accessories such as the radio or heated seats acting up
• A battery or charging warning light on the dash (see below)
• A swollen or cracked battery case, corrosion on the terminals or cables, or a sulphur (rotten-egg) smell from the battery

A battery or charging warning light that comes on while you're driving can't wait for a fall check. CAA-Quebec advises cutting back on electrical accessories and having it checked right away, because a failing charging system can cause a sudden loss of electrical power. If the vehicle starts to lose power or the light is joined by other warnings, stop somewhere safe and call for help rather than pushing on.

Test first, then decide

A battery that starts the car today can still be close to the edge, and a test shows where it stands. It also shows whether the battery is the weak link at all. Transport Canada's winter preparation advice pairs the battery with the charging system and belts, and recommends replacing weak batteries before they fail.

A new battery won't last long if the alternator isn't keeping it charged or the belt that drives the alternator is slipping. That's why a battery and charging-system test looks at more than the battery alone. If the question is which part is failing, telling a battery problem from an alternator problem comes down to the symptoms and testing.

If the vehicle is already due for an oil change or other routine maintenance this fall, that visit is a convenient time to ask for the battery test as well.

What the CCA number means

The CCA rating on a battery label is a cold-start rating. Under the Battery Council International definition, it's the current a new, fully charged 12-volt battery can deliver for 30 seconds at -18°C while holding at least 7.2 volts. A battery loses some of that ability as it ages, which is why a test compares what it can deliver now with what it's rated for. When a replacement is needed, it should match the type, size and ratings the vehicle maker specifies, such as cold cranking amps and reserve capacity.

Block heaters and warm-up time

When to plug in a block heater

If your vehicle has a block heater, it warms the engine before you start it. CAA-Quebec points out that an easier start draws less from the battery. There's no single official temperature for plugging in. CAA-Quebec suggests it once the temperature drops below -5°C, and calls it highly recommended at -15°C or colder. Your owner's manual may have its own guidance.

You don't need to leave it plugged in all night, but the sources differ on how long is enough. Natural Resources Canada recommends a timer set to come on no more than two hours before you start the engine, while CAA-Quebec says three to four hours before driving is enough.

How long to warm up the car

Long idling doesn't do the engine or the battery any favours. Natural Resources Canada says idling for more than 30 seconds has no benefit for the vehicle, and its 2016 winter driving tips say that in most cases you need no more than two to three minutes of idling, even from an extreme cold start (its example is -20°C). NRCan calls driving for a few minutes the most efficient way to warm the engine, drivetrain and cabin.

As BCAA notes, idling won't fully recharge the battery either. CAA-Quebec adds that a remote starter can weaken a battery, especially if the engine shuts off after a set time and has to be restarted.

Never warm up or idle a vehicle in a garage, and that includes using a remote starter while it's parked inside. Health Canada advises against idling in a garage even when the door is open, and HealthLink BC warns against idling in an attached garage because exhaust can carry carbon monoxide into the house.

If the heater still blows cold once the engine has warmed up, that's a cooling-system question rather than a battery one, and why a car heater blows cold air has causes of its own.

Hybrids and vehicles that sit

Hybrids and other electrified vehicles also have a separate 12V battery. Toyota Canada says the 12V batteries in its electrified models are affected by cold weather and need the same care as the battery in a gas vehicle.

Toyota Canada also warns that on some of its models a battery state sensor is mounted on the negative terminal, and it highly recommends not disconnecting the battery terminals under any circumstances. Leave the terminals alone and let a technician handle anything that involves disconnecting the battery.

A vehicle that sits for weeks in the cold, such as a second car or one left behind while you travel, can drain its battery. Toyota Canada notes that this can also cause damaging crystal buildup, and suggests a trickle charger or battery tender for a vehicle that will be parked for a long stretch. Because of the terminal warning above, check your owner's manual or ask a technician how a charger should be connected on your vehicle before using one.

If the cold has already caught up with you

If the car already won't start, the sound it makes is a clue: a single click, rapid clicking or silence can each point to a different cause, and the battery is only one possibility.

For a jump-start, call roadside assistance or follow the procedure in your owner's manual, since connection points and steps differ between vehicles. A car that starts after a jump still needs a battery and charging-system test.

Tire pressure changes with temperature too, Natural Resources Canada notes, so a tire-pressure light that comes on in a cold snap is worth checking.

Common questions

My battery went flat once. Does it need replacing?

Not necessarily. Lights left on or a long stretch parked can drain a healthy battery. After a full recharge, a battery test shows whether it has recovered or lost capacity. Don't leave it sitting flat in the cold for long, since Toyota Canada notes a drained battery can be damaged that way. If it keeps going flat, the cause may be the charging system or something drawing power while the car is parked, and that's worth having diagnosed.

Is it worth testing a battery that's only two years old?

If it shows any of the warning signs above, yes, whatever its age. Heat and short trips can shorten a battery's life. With no warning signs, it can usually wait until the three-year mark, when CAA-Quebec suggests having the electrical system checked. After that, CAA-Quebec recommends testing the battery regularly, and a fall test fits ahead of the outflow season.