Wireless batteryless TPMS

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YairK

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Hello everybody,

I am doing a report about wireless TPMS, and I heard about products (the sensors in the valves) that do not need batteries at all to operate and transmit the data. Is that correct??
there are all sort of energy harvesters mechanisms that generates power from vibrations or pressure (piezo-electric, electromagnetic, active RFID, etc.).

I am trying to understand whether TPMS are becoming battery-less, and if so, with which mechanism?

Thank you in advance,
Yair
 
I've not seen any batteryless ones, or not so far.
The ones I've seen all have a small lithium cell inside the moulded casing.

The battery life is good and they generally outlive the tyres then get replaced.
Most manufacturers do not want to sell something that will never need replacing!
 

The listed lifetime is 6-years so that is about half-way through a second set of tires at the industry average 12k miles/year and 50k per set of tires (those are averages - I don't need to hear how your tire lifetime is better or worse).
Unfortunately, a TPMS costs about $70 per tire and labor is extra if you are not already changing tires.

So, I like this idea except generating a charging cycle inside a tire with mechanical components is difficult without creating an imbalanced weight - and therefore a vibration.

I think the best charging method will be a wireless charging system. Unfortunately, rechargeable lithium batteries have a much higher self-discharge rate than one-time use (primary) lithium cells as are used in the current system.
 
Very interesting gophert.
When saying "wireless charging system" you mean that the user will recharge it once in a while? or did you meant that a recharging system will be set on the chassis in front of every wheel?. If you meant the latter, than there is also a solution in the market to recharge/operate the system using RF reader. the sensors will be some sort of RFID tags that will get charged from radio waves.
there are TPMS systems starting at 40$ (you can install it by yourself), and easily reaching 150$.
 

It all seems pretty pointless, the current system with non-rechargeable batteries lasts 6+ years, a rechargeable system is unlikely to reach that age, never mind exceed it, before the batteries need replacing.
 
Thanks Nigel Goodwin, but are you saying that "energy harvesting" is not effective? we should never use rechargeable batteries?.
What about using Super capacitor? they have longer life span than that of a battery.
 
YairK said:
Thanks Nigel Goodwin, but are you saying that "energy harvesting" is not effective? we should never use rechargeable batteries?.
Click to expand...

It's effective in the right place, as are rechargeable batteries, but the right place isn't in a TPMS where non-rechargeable batteries give longer life.

What about using Super capacitor? they have longer life span than that of a battery.
Click to expand...

I suspect you would be sorely disappointed, both in Super caps performance, and in their lifespan.

A non-rechargeable Lithium battery has a nice flat discharge curve, and a long life - Super capacitors have neither.

A good place for a Super capacitor (or multiples) is across such a lithium battery, so as to supply high current pulses which the Lithium can't.
 
I've just got a dashcam that can work directly with these sensors; they just replace the tyre valve dustcaps and use lithium cells than can be replaced when needed..
**broken link removed**

I've not found any at a sensible price in the UK yet, though...
 

I bought one from China, cost about £20-25, four external mounted sensors, and a dashboard mounted display with a solar panel on top to keep it charged.
 
Nigel Goodwin said:
Super capacitors have neither.
Click to expand...
Not sure it is correct, SuperCaps can last 10-15 yrs if used properly,
see here **broken link removed**.
also,
The supercapacitor is often misunderstood; it is not a battery replacement to store long-term energy. If, for example, the charge and discharge times are more than 60 seconds, use a battery; if shorter, then the supercapacitor becomes economical.
Click to expand...
So maybe it is a good alternative for a battery.

But...after reading the info from the link I shared, I now afraid that if the car won't move for a month or two, the super capacitor will discharge completely, making the entire system drained and not functional anymore. is that make sense?
 
YairK said:
Not sure it is correct, SuperCaps can last 10-15 yrs if used properly,
see here **broken link removed**.
also,
Click to expand...

In practice Super capacitors don't have a great lifespan.

So maybe it is a good alternative for a battery.
Click to expand...

In my opinion they are pretty useless as a battery, as they don't provide anything like a stable voltage.

But...after reading the info from the link I shared, I now afraid that if the car won't move for a month or two, the super capacitor will discharge completely, making the entire system drained and not functional anymore. is that make sense?
Click to expand...

Yes, it's a bad choice - and while existing battery based are so good why try and change it?
 
Nigel Goodwin said:
and while existing battery based are so good why try and change it?
Click to expand...
I am bringing an answer from the web:
source: pmctire.com
* I think they mean "faster" then an indirect TPMS, which uses the ABS system to calculate the pressure, and it takes 20-60 minutes to get updated.
 
Thanks everyone for your answers, but I still can't reach a conclusion about that industry- "battery-free TPMS".... is it just a ferry-tale??
 
YairK said:
Thanks everyone for your answers, but I still can't reach a conclusion about that industry- "battery-free TPMS".... is it just a ferry-tale??
Click to expand...

Presumably you mean 'fairy tale' - and I would say so, particularly for general use. There's no advantage to what you suggested, and it's likely to be more expensive and have a shorter life than a battery.
 
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