If you’ve ever found yourself standing next to your vehicle pressing your remote with no response, chances are your car key battery is dead. I’ve worked with countless drivers who were caught off guard by a failed key fob—something that can be prevented with just a little know-how. In this article, I’m going to break down the types of batteries used in car keys and fobs, what the numbers on those batteries mean, and which ones go in which vehicles. This is your go-to guide for keyfob battery replacement—no guesswork, no confusion.

Modern car key fobs almost universally use coin-style lithium batteries, often referred to by their IEC part numbers like CR2032 or CR2025. The first digit refers to the type of chemistry. In this case, the “C” stands for Manganese-dioxide/Lithium. The second digit refers to the shape. In this case the “R” stands for Round. The next two digits refer to the diameter, and the last two refer to the height of the battery in tenths of a millimeter. You’ll typically find one of the following:

Battery #  —  Voltage — Size (Diameter/Battery Thickness mm) — Amp-Hour Rating (mAh)
CR2032  —  3V —  20 x 3.2 —  ~225 mAh
CR2025 —   3V —  20 x 2.5 —  ~170 mAh
CR2016 —   3V —  20 x 1.6 —  ~90 mAh
CR1632 —   3V —  16 x 3.2 —  ~130 mAh
CR2450 —   3V — 24.5 x 5.0 —  ~540 mAh

The higher the last two digits, the thicker the battery—and generally, the more charge it can hold.

If you’ve got a keyless entry system, chances are it uses one of the three most popular coin batteries: CR2032, CR2025, or CR1620. Here’s what I see most often in my garage:

The Workhorse
This is by far the most common car key battery. Brands like use this battery in everything from keyless entry fobs to proximity push-start keys. With a capacity of around 225mAh, a CR2032 will typically last 3–5 years, depending on usage.

Slightly Thinner, Still Popular
use the CR2025 in many of their remotes. It’s the same diameter as a CR2032 but thinner. That difference in thickness means less power (around 170mAh), so you might find yourself needing a keyfob battery replacement more frequently.

– For Compact Keys
Some keys use smaller coin cells like the CR1620 or CR1632. These batteries are narrower and designed for tight spaces, but they also run down faster. Expect to replace them every 2–3 years depending on climate and usage.

– The Heavy Duty Option
Vehicles with more power-hungry remotes—like —may use the larger CR2450. It’s thicker and wider, with a capacity of over 500mAh. These are less common but pack a punch when needed.

I always recommend checking the car key battery every two years or whenever you notice these warning signs:

• Shorter remote range
• Intermittent locking/unlocking
• Keyless start failure
• Dashboard message: “Key Battery Low”

I can’t stress this enough: don’t cheap out on Car Key Fob batteries. I’ve seen customers use off-brand or expired batteries that only last a few weeks. Always buy fresh, lithium (not alkaline) batteries from trusted brands like Duracell, Panasonic, Toshiba, or Energizer.

Some online sellers also stock multi-packs, but check the expiration date—coin cells have a long shelf life (up to 10 years), but only if stored properly.

If your fob stops working, try holding it closer to the push-start button or door handle. A weak battery might still work at close range.

Some push-button start vehicles won’t run at all if the key battery dies.

Don’t insert multiple thinner batteries (like two CR2016s) in place of one thicker CR2032. It’s unsafe and can damage the fob.

©, 2025 Rick Muscoplat