The situation when the battery suddenly goes down in the key to the car often takes the owner by surprise. This can happen at the most inopportune moment: at the entrance to the mall, in the parking lot near the office or in the garage in the dead of night. Modern systems of access and start of the engine Keyless Go or Start-Stop They require constant power to transmit a radio signal, and the slightest decrease in charge makes the key fob a useless piece of plastic.
Panic at this point is not worth it, as car manufacturers provide emergency scenarios in case of discharge. Mechanical key, built into the key fob, and special reading zones in the cabin allow you to get inside and start the engine even with a fully discharged power element. Understanding the design of your device and knowing the algorithm of actions will help solve the problem in a few minutes.
In this article, we will discuss in detail why the charge goes down, how to urgently open the car and start it, as well as give recommendations for the choice of new batteries. You will learn to distinguish between discharge symptoms and learn what tools you will need to quickly replace a battery without damaging the body.
Signs of discharge and causes of key fob failure
The first alarm bell that indicates that the battery will soon die is a decrease in the range of the signal. If before the car opened from a distance of 10-15 meters, now you have to come close or press the button several times. The dashboard may also catch fire. discharge-indicatorThis is often a schematic image of a key or battery.
Another sign is the unstable operation of functions. For example, the boot button will react once in a while, or the keyless system will no longer recognize the owner, even though he is near the door. In some models with displays on the key fob, such as BMW or LexusThe screen starts to dim or display a message about a low charge level.
The main reason for the failure is the natural wear of the lithium cell, the resource of which is on average 2-4 years, depending on the intensity of use. However, there are other factors that accelerate the discharge:
- 🔋 Frequent pressing of buttons outside the range of the car when the signal is wasted.
- ❄️ Extremely low temperatures that reduce battery capacity.
- 📡 Constant location of the key fob next to sources of powerful electromagnetic radiation.
It is important to distinguish between battery discharge and software failure or failure of the device itself. If replacing the power supply does not help, a reflashing or board repair may be required.
Emergency opening of the car without charge
When the battery is completely dead, the electronics stop responding to the pressing of the buttons. In this case, it is necessary to take advantage of mechanicallywhich is hidden inside the casing of the key fob. In most modern models, such as Toyota, Kia or FordTo extract the key, you need to press the retainer and pull out a metal sting.
The larva of the driver's door lock is often hidden under a decorative stub on the handle. Carefully tuck it with a flat object or the key sting itself to gain access to the lock. Insert the key smoothly, without excessive effort, so as not to damage the mechanism that could sour from time to time.
⚠️ Warning: After opening the door with a mechanical key, a regular alarm may be triggered. Don’t be afraid of loud noises, this is a normal security response. To turn it off, you must immediately insert the key into the ignition lock or press the start button (if the system reads the chip).
In some vehicles, for example, in models. Tesla new MercedesThe mechanical opening for the key may not be at all or it is hidden very deep. In such cases, manufacturers recommend using special applications on a smartphone or bringing a discharged key fob to a special area.
How to start the engine with a discharged key fob
After getting into the cabin, the owner faces the following task - start the engine. System system Start-Stop It won't work by pressing a button, because the immobilizer can't see the tag. To solve this problem, engineers have provided launcher.
You need to find a readout area where the car’s induction coil can “break through” the weak signal from the dead battery. The location of this zone depends on the brand of the car. Most often it is located in the area of the steering column, in the cup holder, in the niche for trifles or directly on the start button itself.
The algorithm of actions is usually as follows:
- 🚗 Attach the key fob with the back side (where the logo is) directly to the engine start button.
- 🥤 Place the device in a special recess in the cup holder, indicated by the key icon.
- 📍 Hold the key fob to the tag on the center console or torpedo.
- ⚡ Press the brake pedal and hold the start button longer than usual (2-3 seconds).
☑️ Emergency launch algorithm
If the vehicle is equipped with a system KeylessSometimes it is enough to simply press the key fob against the start button with your foot or hand and press it. In models Renault or Nissan Often you need to insert the fob case itself into a special slot that resembles a hole for a conventional key card.
Replacement of the power supply with their own hands
After successful start of the engine and arrival in a safe place it is necessary to replace the seated element. For this procedure, you will need a new one. battery (most often CR2032 or CR2026) and a thin screwdriver or plastic spatula.
The process of disassembly depends on the design of the body. Most key fobs consist of two halves connected by latches. Find the junction of the halves and carefully separate them, acting as a lever. The main thing is not to damage rubber seals and electronic board.
| Model car | Type of battery | Features of replacement |
|---|---|---|
| Toyota / Lexus | CR2032 | The body is on the latches, you need to be careful. |
| BMW | CR2450 | Often the entire module is required to be removed. |
| VAG (VW, Audi) | CR2032 | The battery could be under the pay-off. |
| Hyundai / Kia | CR2032 | Simple design on screw or latch |
When installing a new battery, observe the polarity: the side with the inscriptions and plus (+) shall look up unless otherwise specified in the instruction. After replacement, collect the body to a characteristic click and check the operation of the buttons.
Can I use batteries from other brands?
Yes, you can. The main thing is to comply with the size (for example, 2032) and the voltage (3V). Brands like Panasonic, Duracell or GP have proven to be reliable. Cheap Chinese counterparts can have less capacity and sit down faster, especially in winter.
Types of batteries and selection of quality element
Lithium disk batteries are used for car keys. The most common types are CR2032, CR2026 and CR2016. The numbers in the title indicate the dimensions: diameter and thickness in millimeters. For example, 2032 means 20 mm in diameter and 3.2 mm in thickness.
It is important to know that the battery CR2032 can be temporarily replaced CR2026They have the same diameter but are smaller in thickness. Contact will be made, but the element may dangle, which will cause the signal to disappear. Reverse replacement (thick to thin) is physically impossible - you just won't close the case.
When buying, pay attention to the date of production. Lithium cells have a long shelf life, but lying goods can lose up to 20% of their capacity. Give preference to trusted electronics stores or automotive departments, avoiding markets with questionable storage conditions.
Check the contact: after replacing the battery, wipe the contacts on the board with an alcohol napkin. Oxidation or fat from the fingers can interfere with normal current, and the key will still not work.
Prevention and useful advice
To avoid the situation of “battery sat down” too often and not become a surprise, follow simple rules of operation. Check the condition of the key fob regularly, especially before long trips or in winter.
Do not leave your keys in places with extreme temperatures. In summer, the interior of the car is heated to 60-70 degrees, which negatively affects the chemistry of the lithium element. In winter, a sharp temperature drop when the key fob is applied to heat can cause condensation inside the housing, leading to corrosion of contacts.
⚠️ Note: If you do not use the car for a long time, remove the battery from the key fob. This will prevent deep discharge and possible leakage of the electrolyte, which can damage the electronic board.
Always have one additional battery pack. They take up a minimum of space in the glove compartment, but can save at a critical moment. It is also helpful to know the location of the emergency readout tag in your particular model so as not to look for it in a panic.
Timely replacement of the battery at the first sign of discharge (reducing the range) is the best way to avoid problems with access to the car.
Frequently Asked Questions (FAQ)
How much does the battery last in the key?
The average service life is 2 to 4 years. This depends on the frequency of use, the model of the car and the quality of the battery itself. In systems with constant signal search (Keyless), the discharge occurs faster.
Can I start the car if the battery is completely dead?
Yes, you can. For this purpose, a mechanical key is used to open the doors and a special reading zone (immobilizer) in the cabin to start the engine, which works by induction even without the key fob power.
Where to buy a battery for the key, if it sat on the road?
CR2032 power supplies are sold in most supermarkets, electronics stores, gas stations and tobacco kiosks. They are standardized and widely available.
Why did the key stop working after the battery was replaced?
Possible reasons: incorrect polarity setting, protective film on a new battery (it must be removed), oxidation of contacts inside the key fob or the need to synchronize (registration) of the key.
Is it dangerous to take the key out by yourself?
With a careful approach, no. The main thing is to use the right tools (plastic blades) so as not to break the plastic latches of the case and not damage the chip. If the body is glued, it is better to contact professionals.