Why a Replaceable Battery Matters in a TPMS Sensor A CR1632 you can change — and a sensor that keeps its identity afterwards — decides whether a TPMS is a maintained part or a disposable one.

A small line in a specification sheet

Most TPMS specification tables list a battery type and stop there. Ours adds two things that matter more than the cell itself: the battery is replaceable, and the sensor does not need re-pairing after a battery change.

Both come straight from the product approval sheet, and together they decide whether the product is serviceable or disposable. Everything below explains why, and what the alternative costs.

Two questions, not one

Buyers usually ask the first question and forget the second.

Can the battery be replaced at all? Many sensors are potted or ultrasonically sealed. That protects them well against water and vibration, but it means the cell is not accessible. When the cell is exhausted, the whole sensor is scrap — including the sensing element, the radio and the housing, all of which were fine.

Does the sensor keep its identity after the swap? This is the one that gets overlooked, and the one that generates support calls. A sensor whose battery can be changed but whose identity is lost on power removal forces a re-pair or a re-learn on that wheel. The customer has to find the pairing procedure and the dealer has to explain it, every time.

A product that answers yes to the first question and no to the second is only half serviceable. Our answer to both is yes: the CR1632 is replaceable, and the sensor does not need re-pairing after replacement.

What no re-pairing means in practice

When a sensor is paired to an app, the app stores the identity it uses to recognise that sensor. The question is whether that identity survives a loss of power.

In a sensor that needs re-pairing, the identity is effectively regenerated or the pairing record is invalidated when the cell is removed. The user then goes back through the pairing flow for that wheel: open the app, enter pairing mode, wait for the sensor to appear, assign it to the correct position. On a four-wheel vehicle that is one wheel if you are careful and four if you are not.

In our sensor the identity persists, so the sequence after a battery change is short:

1. Open the sensor housing as instructed.
2. Replace the CR1632.
3. Refit the sensor to the valve.
4. Confirm the reading returns in the app.

There is no re-pairing step, no re-learn tool and no workshop visit with a programming device. That is the whole point of the design decision.

The hidden cost of a sealed sensor

A sealed sensor looks cheaper on the quotation, because you are buying a complete unit with nothing to service. The cost appears elsewhere, and it appears three times.

Per-wheel replacement cost. Instead of a coin cell, the customer buys a complete sensor — housing, electronics, sensing element, radio, packaging and freight. The part that failed is the cheapest part in the assembly.

Downtime and labour. Changing a coin cell is a two-minute job for a rider with a screwdriver. Diagnosing a dead sensor, ordering a replacement, waiting for delivery and fitting it is a different category of job, and on a commercial vehicle it may mean the vehicle is off the road.

Waste and stock complexity. If batteries cannot be changed, every dealer has to stock complete sensors in every variant and every wheel-position marking. That is a much larger inventory than a box of coin cells, and it grows with every vehicle class in the range.

There is a fourth, softer cost: what the customer concludes about the product. A tyre-pressure system exists to prevent being stranded by a tyre. A system that itself becomes the reason for a workshop visit teaches the user something about the brand that no marketing will undo.

Why the battery and identity decisions belong together

These are two separate engineering decisions, made at different times by different people.

The mechanical decision is whether the housing gives access to the cell while still sealing against water and dust. Our platform is specified for 5% to 95% humidity, non-condensing, and for operating temperatures from −20 °C to +80 °C with storage from −40 °C to +85 °C. A replaceable cell and a sealed housing are not in conflict, but they have to be designed together.

The firmware decision is whether the sensor's identity and any calibration or configuration data live in volatile or non-volatile memory. Getting this wrong is not visible in a sample unit; it only appears when a real customer changes a real battery. Ask about it explicitly.

What to ask a supplier

1. Is the cell user-replaceable, and what cell is it? "Long-life battery" is not an answer. Ask for the cell type and whether it can be changed without destroying the housing.
2. After a battery change, does the sensor need re-pairing or re-learning? Ask this precisely. A vague yes is usually a no.
3. What does the user physically have to do? Ask for the written procedure. If it needs a tool the customer does not own, it is a workshop job.
4. What happens to the sensor's identity on power loss? This is the firmware question behind the paperwork, and it reveals whether the supplier has thought it through.

If the answer to question two is that re-pairing is needed, the product is still usable — it is simply a product with a service cost your dealer network pays every time a cell runs flat.

Where we stand

Our sensor uses a replaceable CR1632 and does not require re-pairing after a battery change. That is stated on the approval sheet, not invented for a blog post. It is one line in a table, and it changes what ownership of the product looks like in service. Every sensor is pressure-calibrated on our own test software before it ships, and we run water-immersion, RF-range and protocol verification in house. Capacity is 30,000 sensor units a month against current supply of more than 10,000 sets a month into the Chinese two-wheeler aftermarket, and certification is handled per market and per project.

If you are specifying a TPMS for a programme and want the service model in writing — what the user does, what the dealer does, what stays inside the app — send us the vehicle and the market. The full specification is on the BPU100 product page, documentation is on the downloads page, and the rest of this series is on the blog index.

FAQ

What battery does the sensor use? A CR1632 coin cell. It is replaceable, and the sensor does not need re-pairing after the battery is changed.

Can the customer change the battery themselves? Yes. It does not require a workshop tool or a programming device. The exact procedure is covered in the documentation supplied with the product.

Do I lose the wheel position assignment when I change the battery? The sensor keeps its identity, so the wheel it is assigned to in the app is unaffected by a battery swap. Confirm the reading returns after refitting, which is a normal check in any case.

Does a replaceable battery make the sensor less water-resistant? No. A replaceable cell and a sealed housing have to be designed together, and this platform is specified for 5% to 95% humidity, non-condensing, and for operating temperatures from −20 °C to +80 °C.