Battery Failure and Reduced Cranking Power

Before we dig into cranking power and battery failure, let’s cover some basic electrical measurements: volts and amperes (amps).

Think of these units of measurement as the electrical equivalent of water pressure and amount of water, respectively. So, in terms of electricity, voltage measures the pressure that pushes electrons through a circuit. Amps, by comparison, measure the flow rate of an electric current.

When testing your battery, some results will report a value in volts, and others in amps.

A vehicle’s cranking power measures the amps a battery can output for a certain period and at a specific temperature. Cranking amps and cold cranking amps are used to determine if a battery can produce enough power to crank the engine.

Cranking amps (CA) are the maximum amount of current that flows through the battery for 30 seconds at 0˚C while maintaining at least 7.2 V.

Cold cranking amps (CCA) are measured via the same test, but at -18˚C.

These measurements help an automotive technician discover any problems within the vehicle’s electrical system. Some examples include:

• corroded battery terminals
• internal battery degradation
• loose cable connections
• poor ground connections
• worn or damaged cables

Any of these issues will reduce cranking power, which will affect the engine’s ability to turn over when the starter motor is engaged.

When you turn on your vehicle by inserting the key or pressing the start button, you close a current to activate the starter, which draws energy from the battery to activate the crankshaft and start the engine. The engine powers the alternator, which recharges your battery.

Starting your vehicle in the summer will need between 100 and 400 amps. In the winter, the typical range is between 225 and 500 amps. The large range accounts for several factors, including the vehicle model itself.

You may have noticed in the previous section the increased range of amps required to start a vehicle in the winter. The cause is the cold weather, which affects the battery in two main ways:

• Oil in the engine thickens, which makes it harder for the engine’s parts to get moving.
• Chemical reactions in a battery slow down as the temperature drops, which reduces its charge.

Your battery will lose about 20% of its charge at 0˚C and nearly half at -18˚C. Meanwhile, your vehicle demands more electricity in the winter: thickened engine oil makes the starter work harder, while the HVAC system, seat warmers, defrosters, windshield wipers, and lights all pull additional current.

That’s why so many batteries fail during the coldest months, leaving drivers and their passengers stranded. They simply don’t have enough power left to keep up.

You can take several steps to help your battery maintain as much charge as possible in winter:

• Use a trickle charger or battery maintainer if your car will sit for long periods of time.
• Drive for longer stretches to help your engine fully charge your battery.
• Use a battery blanket overnight to help improve the battery’s charge for your morning commute.

Any 12 V lead-acid battery lasts from three to five years. As you try to diagnose your battery problems, keep its age in mind. It may simply be growing old, and a new battery makes sense, especially if you’re about to embark on a long trip.

Review these checklists to see if it is indeed time to get a new one.

Starting problems:

• engine doesn’t start
• car takes a long time to turn on
• difficulties starting engine, especially in cold weather
• frequent need for boosts or jump-starts
• weak or laboured cranking in winter conditions

Electrical issues:

• all headlights dimming at the same time
• dash lights dimming during ignition
• multiple electrical issues occurring simultaneously

Warning lights:

• check engine light on
• battery warning light on

Test results:

• battery reads less than 12.4 volts on multimeter
• battery voltage below 12 volts on battery tester

Physical or visual damage:

• blue foam on or around terminals (corrosion from leaking acid)
• misshapen battery case (should be rectangular, not angular or bumpy)
• visible cracks or leaks
• unpleasant or burning smell
• heavy corrosion and grime buildup
• battery appears physically damaged or “in poor shape”

Canadian winters test every battery, but understanding cranking power helps you stay ahead of potential failures.

Monitor your battery’s voltage twice a year, keep the terminals clean and corrosion free, and watch for warning signs like slow cranking or dimming lights. Staying on top of battery maintenance can help you pass “the Canadian battery test.”

For questions about battery testing, winter maintenance, or finding the right replacement battery for your vehicle, visit your local NAPA Auto Parts store to speak with an expert. You can browse our wide selection of batteries, battery chargers, and winter accessories online at NAPA Canada.