Tyrepal battery change

Taken from Tyrepal website. They are internal sensors as fitted to Bailey caravans, with non replaceable batteries.
Hope this helps

It looks like you have the internal sensors, so it will be tyres off to change them.

https://www.tyrepal.co.uk/product/internal-pressure-sensor/

They are supposed to last 3-5 years but this would be in a car, lower mileage would give a longer life.

They are listed at £37.50 each and the batteries are non replaceable but I am sure someone will have tried.

Thanks for  the answers. Van is 7 years old now, but with limited mileage. I'm not sure if it is the batteries that's the problem. All 4 sensors register with the display unit, but then when driving I only get readings from 2 or 3 randomly, never all 4. 

My last post crossed in the ether with the one from Burgundy

If your tyres have never been replaced and are 7 years old they are due for replacing. 

So a big expense on the cards perhaps.

Tyres were replaced at last service. Should have had the sensors replaced at the same time.

Same as the VW ones. Tyres off and new sensors bolted to the rims. Don't believe mileage would make any difference to battery life as they always transmit the pressure whether or not the transmission is being received by the control unit so age only for the battery life I think

I went through this with our last van - a Bailey - with internal sensors.  The sensors started to get unreliable after three and half years.  So - without thinking too much, I went through the process of buying a new set of sensors (4) and getting my local garage to take the tyres off, replace the sensors at a cost of £10 for each of the 4 tyres.  What an expense!!

The current van didn't have TPMS fitted - I bought 4 external sensors (£25 each) and obviously fitted them myself.  I change the batteries every year since the cost of bulk buying those little batteries is peanuts - plus I change the "O" rings and make sure there's a dab of silicone on the cover to keep moisture out.

So simple, quick and cheap to do.  I had in the back of my mind that internal sensors would be better than the external ones but I have to say that there isn't any difference in terms of performance and I would never replace internal sensors again.

Yes. Tyrepal have now advised me that external sensors can be fitted to the existing internal sensor valve stems. Thats the way to go. 

The sensors do not transmit until they detect rotation of the wheel so mileage makes a big difference. The OP sensors appear to have lasted 7 years.

That is correct. Takes a few minutes of rotation before the pressure registers on the display unit.