Battery-free TPMS

Boon Docker wrote:

ktmrfs wrote:
virtually ALL TPMS systems rely on tire rotation to wake up the system to conserve battery life. the ones inside the tire have a battery. I seriously doubt there are any that do not use a battery.
Even the external systems sense roation to wake up the system.

centrifical rotation by itself is not a way to generate power.

Yes there are batteryless TPMS sensors on the market that use "SAW" technology.

Maybe I'm misunderstanding how these work, but it looks like the passive sensor "replies" to a "query" from an antenna. Without input from the antenna, there would be no action by the sensor. You may not need a battery in the sensor but there would have to be an antenna constantly querying the sensor. Or am I "unclear on the concept". :)

ktmrfs wrote:
virtually ALL TPMS systems rely on tire rotation to wake up the system to conserve battery life. the ones inside the tire have a battery. I seriously doubt there are any that do not use a battery.
Even the external systems sense roation to wake up the system.

centrifical rotation by itself is not a way to generate power.

TST's sensors turn on when installed and only shut off when removed. The monitor will shut down when running on the internal battery, but just a tap will wake it up so it can update with the current readings before rolling out.

Hmm, why not a sensor mounted in the rim, powered by electromagnetic induction as new phones can be charged? I hear it is a pain moving sensors back and forth to winter and summer tires, costing more than the cost of the product itself over a few years. SIL says he has sensors in both sets of tires and after changes the sensors often fail to be recognized by the truck.

ktmrfs wrote:
virtually ALL TPMS systems rely on tire rotation to wake up the system to conserve battery life. the ones inside the tire have a battery. I seriously doubt there are any that do not use a battery.
Even the external systems sense roation to wake up the system.

centrifical rotation by itself is not a way to generate power.

Yes there are batteryless TPMS sensors on the market that use "SAW" technology.

GordonThree wrote:

fj12ryder wrote:

ScottG wrote:
Probably be possible but not necessary. We have newer Challenger that has no battery in the sensors at all and works great.
That's the kind of thing I'm looking for.

Could you expand on this? How do the sensors work without batteries?

There's no sensor inside the wheel. Computer uses voodoo or maybe math, ambient temperature and wheel speed to calculate air pressure. My guess

some cars look at the abs sensors in the car. if there is a difference in pressure there is a slight variation in tire diameter. not much, but enough that it is possible to notice the difference. they use this to look for a low tire.

However these have mostly gone away.

you may not think there is a battery in the internal sensor, but there likely is. they will easily last 5 years or more under typical use. Often 7-10 years.

fj12ryder wrote:

ScottG wrote:
Probably be possible but not necessary. We have newer Challenger that has no battery in the sensors at all and works great.
That's the kind of thing I'm looking for.

Could you expand on this? How do the sensors work without batteries?

There's no sensor inside the wheel. Computer uses voodoo or maybe math, ambient temperature and wheel speed to calculate air pressure. My guess

ScottG wrote:
Probably be possible but not necessary. We have newer Challenger that has no battery in the sensors at all and works great.
That's the kind of thing I'm looking for.

Could you expand on this? How do the sensors work without batteries?

RCMAN46 wrote:
What I would consider ideal would be an internal sensor that had a rechargeable battery that is charged by the centrifugal action of the tire and wheel.

Yes, this would be ideal, but there is a net zero force at the interior of the rim. About the only thing I could imagine as an electrical power source is a piezoelectric device, but those generate such a small amount of energy I don't think they would work.

virtually ALL TPMS systems rely on tire rotation to wake up the system to conserve battery life. the ones inside the tire have a battery. I seriously doubt there are any that do not use a battery.
Even the external systems sense roation to wake up the system.

centrifical rotation by itself is not a way to generate power.

road-runner wrote:

RCMAN46 wrote:
What I would consider ideal would be an internal sensor that had a rechargeable battery that is charged by the centrifugal action of the tire and wheel.

Would this be possible? All of the generation techniques I know of require motion or a temperature differential. Maybe something could be done with a big stationary magnetic field near the tire?

If there was a device that produced power using only centrifugal force, couldn't you just put a brick on top of it to get free unlimited power?

Probably be possible but not necessary. We have newer Challenger that has no battery in the sensors at all and works great.
That's the kind of thing I'm looking for.