Battery-free TPMS

wa8yxm wrote:
There multiple TPMS systems. one is hard wired and uses a pipe to the hub.. I see this on trucks but can tell you nothing about it

Those are not a TPMS, rather they're an ATIS, an "Automatic Tire Inflation System". There's a dash mounted controller that tells an on board compressor/solenoid system when to add or remove air to maintain driver selected pressure parameters based on the current load and road conditions. Trucks used in agriculture for field loading, etc., often use lower pressures to increase the contact area in the fields to minimize soil damage and increase traction. When they leave the fields, the driver simply dials the pressure up to highway speed levels on the fly.

I've never heard of one that uses centripetal force to power the sensor. But replacing the batteries is pretty much no big deal. I've changed probably three batteries over the last five years. They are less than a buck each, so I figure that's not bad. I do take mine off when the unit is in storage. And I don't travel as long or as often as some people either.

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?

There multiple TPMS systems. one is hard wired and uses a pipe to the hub.. I see this on trucks but can tell you nothing about it

one uses teh ABS sensors (A low tire spins faster)

The Rest use radio. I know of none that do not use batteries.

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.

Then the sensor would shut off when battery is low for times when tire and wheel are inactive for an extended time.

That way I could still check pressures each morning before I break camp.

Some of the no-battery TPMS systems don't use an in-wheel sensor at all. Called "indirect" TPMS systems, they rely on software and the wheel speed sensors to detect a low-inflation tire. If all tires were equally low, an alert would not be detected. With such a system you can for instance freely swap summer and winter wheels. No sensors to deal with, no system re-programming, etc.

I like the external ones with the removable battery cap that take a button cell. I bet the no battery ones are expensive, probably work on the same principle as a self winding watch...

GordonThree wrote:
The advantage oem tpms have is they're inside the cavity of the tire and wheel, so they have all sorts of room for a larger module.

The after market ones have to live on the end of the valve stem.

Yeah, that's why I was thinking it would be a great time to install them while tires are being balanced. Not much more work to dismount and install sensors.
I just can't find any manufacture who has adapted the technology to trailers yet.

The advantage oem tpms have is they're inside the cavity of the tire and wheel, so they have all sorts of room for a larger module.

The after market ones have to live on the end of the valve stem.