How to Find the Correct Battery for a Car Key - A Guide for Locksmiths

A wrong or dead key battery can turn a simple job into callbacks and complaints. Worst-case, the customer ends up locked out or the car won’t start – which means more drive-time and a very unhappy driver.

Using the wrong key battery can lead to poor performance as the key may not work consistently, customer dissatisfaction with callbacks/complaints can hurt your reputation, and wasted time and money, repeated trips to the job site eat into your profits.

That’s why it’s crucial to identify the correct key battery the first time. And with Keyless City, it’s easier than ever.

Here’s how you can use Keyless City’s YMM search tool to find the right key battery:

1. Visit Keyless-City.com
   Head to our website and navigate to the search bar.

2. Enter the Year, Make, and Model of the Vehicle
   Use the YMM search feature to identify the specific key for the vehicle. This ensures you’re looking at the exact product designed for that car.

3. Scroll Down to the Product Description
   Once you’ve found the key, scroll down to the product description. Here, you’ll find detailed information about the compatible key battery.
   

4. Click the Link to Add the Battery to Your Cart
   We’ve made it easy for you! Simply click the link provided to add the key battery to your cart and complete your purchase.

It’s that simple! With Keyless City’s YMM search tool, you can save time, reduce errors, and keep your customers happy.

If you can’t (or don’t want to) use YMM, open the fob itself. Most key fobs have a little notch or seam – open it carefully with a small screwdriver or pick. Inside you’ll find the key battery and its one-letter-four-digit code engraved (e.g. “CR2032” or “CR2025”). If the key battery is dead, pop it out and read the code on the old cell, or check the owner’s manual. Then grab an exact match. If your instincts doubt it, the manual or a quick online reference will confirm the right key battery/cell.

To save even more time, consider stocking up on the most common car key batteries. Here are a few customer favorites:

• CR2032: 20mm diameter, 3.2mm thick. The jacked-up bodybuilder of key batteries. Most modern cars (Toyotas, Hondas, Nissans, etc.) use these. Lots of capacity – they’ll last ages even if you use remote-start or have extra fob electronics.

• CR2025: 20mm diameter, 2.5mm thick. Same diameter, thinner. Common in older or simpler fobs. Less juice than a 2032, so it tends to die faster if the fob is used heavily.

• CR2016: 20mm diameter, 1.6mm thick. The thinnest of the bunch. Found in some very basic remotes or alarm keypads. Least power of the lot.

• CR2450: 24.5mm diameter, 5.0mm thick. Big-boy battery. Found in many luxury or performance car fobs (BMW, Mercedes, some GM/Chrysler, etc.). Huge capacity, but also physically larger.

• Others: There are smaller ones like CR1632 or CR1620 on a few remotes. If you see a different code on the key battery, trust it exactly.

Real-world hacks to save time on the job:

• Battery Tester: Keep a coin-cell tester or a small multimeter in your kit. If a key still misbehaves after a swap, open it and test the new cell. Even “fresh” batteries can be bad out of the package. Testing is way faster than re-learning a fob or running diagnostics.

• Clean Contacts: Sometimes it’s not the key battery – it’s the contacts. Give the spring and pads a wipe. Dust, pocket lint, or corrosion can act like a dead battery. A little isopropyl or contact cleaner and a cotton swab can save a call.

• Small Spares: After a couple weeks on calls, you’ll see which cells your area burns through. Always carry packs of CR2032, CR2025, CR2016, CR2450, and a few CR1632. Keep them in labeled packs or a small organizer. It’s golden to have the right cell on hand instead of making a parts-store run.

• Open Fob Tools: In addition to a tester, have a tiny magnet (to fish out anything that drops into the console), and a plastic pry tool. These make the job cleaner and avoid breaking the case. If a fob shell cracks, you can sometimes tape or clip it to get the job done – just remember to replace it fully later.

Watch for early warning signs so you can swap the key battery before it dies completely:

• Weak Range: If the owner has to press the key right up to the car door for it to work, the key battery’s low. When they mention “it worked better last week,” it’s probably time.

• Intermittent Function: Buttons only work occasionally, or only if held down. One press, no beep, second press works – classic dying cell behavior.

• Dashboard Warning: Many cars flash a “key battery low” or “fob battery low” alert. Don’t ignore it. If the user saw it and still waited, use that as a cue.

• Slow Starts: On push-start cars, a weak key battery can make the start button blink or hesitate. If it’s sluggish, swap it.

Lithium coin cells typically last about 2–3 years in normal use. If a key battery is approaching that age (or has a warning), just swap it and be done. 

Always insert exactly the key battery the key calls for. Never jam in something thicker or thinner as a shortcut. A wrong-size cell can damage the fob and ruin the electronics. Here are some other traps to dodge:

• Heat Kills: Leaving fobs or spare cells baking in a hot car or garage will kill them faster. Store your spare key battery in your climate-controlled van or shop, not in the sunshine.

• Static Shock: In very dry conditions, an electrostatic zap can spike a key battery or the fob circuit. If it’s a really dry day, ground yourself or briefly touch metal before handling the fob.

• Rough Treatment: Keys hate getting dropped or crushed. Replace any batteries you pick out of dented/bent cases. 

• Loose Case: If a key shell is cracked or wonky, the key battery can knock around inside. Fix or tape up cracked plastic before you leave, or plan to re-case the key. A loose shell means intermittent connection no matter how good the key battery.

When it’s go-time:

1. Open Carefully: Find the seam/notch and use a small screwdriver or pick. Twist gently – the plastic is meant to flex, not break.

2. Polarity: Check the old key battery. The flat side is usually “+.” Make the new coin’s plus match the same way. Many fobs even have a tiny “+” marking. Putting it backward will just give you a dead key.

3. Seat Firmly: Press the new key battery completely under the contact springs or clip. You should feel it snap in. If it rattles or sits too high, it’s not fully seated – re-seat it.

4. Test Before Closing: Before clicking the fob shut, test the key. It should lock or unlock the car at once. If it doesn’t, reopen and check alignment. A loose coin or bit of debris can block it.

5. Close It Up: Snap the halves back together or replace screws. Ensure there’s no gap. Now hit the door lock or start button one more time to be sure.

A surprising number of callbacks happen because someone missed a tiny screw or didn’t press the battery fully in.

The usual suspects you should stock: CR2032, CR2025, CR2016, CR2450, and a handful of CR1632/CR1620 if you work on BMWs or similar. Buy them in bulk packs (50-100 count) online. Tip: label the packs with the buy date and try to use older ones first. Keep them in clear, labeled bags or a small tackle box. 

Never forget to recycle the old key battery/cells. Many hardware stores, battery stores, or recycling centers take them for free.

For longer life, treat these tiny cells right. Extremes of temperature zap them. Don’t store spares in a hot car or let fobs bake on the dash. If you get a bulk pack and stash it in a toolbox, test them with a meter every few months. A coin cell left in your van for a year can lose voltage slowly. Keep spares in a cool, dry place.

Also, keep the fobs themselves safe. Moisture is a killer.

Stay sharp and keep those key batteries flowing smoothly.