Battery Size Group 121R

Group Size 121R Battery: What You Need to Know Before You Replace It

If you're looking for a smaller, compact battery that’s designed for lighter vehicles and economy cars, the Group Size 121R battery is likely what you need. It’s commonly found in older compact cars that don't require high cranking power, but still need reliable starts—especially in colder Canadian climates.

Battery Specs, Dimensions, and Price in Canada

The Group 121R battery is compact, measuring approximately 8.2 inches (L) x 6.8 inches (W) x 8.6 inches (H). It’s a 12-volt battery, usually rated with Cold Cranking Amps (CCA) between 500 to 600, Cranking Amps (CA) from 625 to 750, and Amp-Hour (Ah) capacities around 40 to 50Ah.

This group size is usually more affordable than larger batteries. In Canada, you can expect to pay between $135 and $190, depending on the brand and warranty. Most come with a 2-year to 3-year free replacement warranty, which is standard in the industry.

Which Vehicles Commonly Use Group 121R Batteries?

This battery group is most often used in smaller Japanese and Korean vehicles. You’ll typically find it in:

Honda Civic (2001–2005)
Hyundai Accent and Elantra
Kia Rio and Spectra
Older Toyota Yaris or Echo models

If you're not sure what size your car takes, check your owner's manual or visit our Car Battery Replacement page for help identifying the correct group.

Alternative Battery Sizes for Group 121R

If you can’t find a Group 121R battery in stock, there are a few alternatives that might work. Just be cautious about tray size and terminal placement:

Group 51R – Slightly taller and longer, but often used as a direct substitute. Dimensions: 9.3" x 5.0" x 8.8"
Group 26R – Similar size but reversed terminal locations; check cable reach before using. Dimensions: 8.2" x 6.8" x 7.8"
Group 35 – Larger footprint and power, may fit if your battery tray has room. Dimensions: 9.06" x 6.88" x 8.88"

It’s always best to double-check before switching sizes. You can read more about how our service works to make the right call.

How to Check If Your Battery Needs Replacing

Here’s a simple checklist if you're unsure whether your Group 121R battery is still in good shape:

Start-up lag – If your engine turns over slowly or takes a while to start, it may be a weak battery.
Voltage test – Use a digital multimeter. A fully charged battery should read 12.6 volts or higher.
Crank test – If voltage drops below 9.6 volts while starting, the battery is nearing the end.

If you’d rather not deal with tools, MobileBattery offers at-home and roadside battery testing, anywhere in cities like Vancouver, Toronto, Calgary, and more. See where we go on our Where We Service page.

How Long Does a Group 121R Battery Last in Canada?

On average, you can expect a Group Size 121R battery to last 3 to 5 years in Canadian conditions. Cold winters, frequent short trips, and lack of regular maintenance can shorten this life span.

Getting your battery checked once a year—especially before winter—can save you from unexpected breakdowns. Whether you're in Montreal, Calgary, or Edmonton, our mobile team is ready to help.