TPMS battery replacement - Maxell CR2450HR EX battery

[Kirkhaan]

Hi there!

I am replacing the battery of my KIA's TPMS. It contains a Maxell CR2450HR-Ex battery.

https://biz.maxell.com/en/primary_batteries/pdf/CR2450HR-Ex_DataSheet_e.pdf

The CR2450HR-Ex battery seems to be hard to find. I see only offers from China (on eBay, Aliexpress etc.).
Additional challenge is to have it with the right solder lugs of course...

Does anyone has advice about where to purchase these kind of batteries? Or maybe suggestions for equivalents that are easier to get?

Many thanks in advance!

[CJay]

https://uk.rs-online.com/web/c/batteries-chargers/non-rechargeable-batteries/button-batteries/?searchTerm=cr2450&applied-dimensions=4294819682

Or does it have to be that exact part?

[Kirkhaan]

Well, it needs to be a heat resistant (HR) type. Rated temperature up to 125C.

That's the difficulty. The common CR2450 batteries available at RS, Farnell, Mouser etc. have a rated temperature of up to 85C.

[amyk]

I suspect an 85C battery will work fine, but simply not last as long if indeed the environment temperature goes up there.

[james_s]

I don't think it will exceed 85C even if you park in the hot sun. I would be comfortable using one of those if I couldn't easily get the higher temperature part. As was already mentioned it may not last as long but since you're able to replace it yourself that doesn't seem like a huge issue.

[bingo600]

What KIA ??

Take & post some pics of the TPMS , and where it's mounted etc ....
Curious about the build up

/Bingo

[Kirkhaan]

I don't think it will exceed 85C even if you park in the hot sun. I would be comfortable using one of those if I couldn't easily get the higher temperature part. As was already mentioned it may not last as long but since you're able to replace it yourself that doesn't seem like a huge issue.

Well, I can replace the battery of the sensor, but not the tires. So I want to avoid to have to go to the wheel center every few years.

[Kirkhaan]

The TPMS is from an KIA Carens (2015, 1.6GDi) and its combined in the valve of the tire. 
The OEM number is 52933-B1100. See below pictures.

I only took the necessary things apart, so not much is revealed from the circuit.

[CJay]

Well, it needs to be a heat resistant (HR) type. Rated temperature up to 125C.

That's the difficulty. The common CR2450 batteries available at RS, Farnell, Mouser etc. have a rated temperature of up to 85C.

I guess as it's not an easy thing to experiment with (wheels on and off the car, tyres demounted, mounted etc.) might be an idea to take a chance on the Chinese sellers.

However, Murata seem to offer a close equivalent to the Maxell part and it's available from Mouser but they don't sell it outside the USA, should be possible to find an EU source?

https://www.mouser.co.uk/ProductDetail/Murata-Electronics/CR2450W-HO5/?qs=GBLSl2AkiruPg8yk10wBXQ%3D%3D

*edit* The datasheet for that cell specifically mentions TPMS as an application and Farnell may be your friend

https://nl.farnell.com/murata/cr2450w-ho5/battery-li-manganese-dioxide-3v/dp/3408811?ost=cr2450w-ho5

[Kirkhaan]

Good find, thanks.

Farnell has no stock unfortunately until beginning of April.

This BR-2450A/FAN from Panasonic would also work. More than €10 per piece though! 
https://nl.rs-online.com/web/p/button-batteries/1839484/

[DavidAlfa]

Given that you already opened everything, maybe you could consider replacing it with a bigger battery?
There's only a bigger type, the CR2477W (High temp version). About 40% higher capacity. It weights only ~3g more.
But the tabs aren't the same...

The wheel needs to be calibrated anyway, so there shouldn't be any problem.

The temperature rating is very important here. See this:

[CJay]

Good find, thanks.

Farnell has no stock unfortunately until beginning of April.

This BR-2450A/FAN from Panasonic would also work. More than €10 per piece though! 
https://nl.rs-online.com/web/p/button-batteries/1839484/

Frustrating when they're out of stock, I can't help wonder if there's some way to harvest power from the wheel motion and store it to power a TPMS.

Still, 10 Euros each is cheaper than a new TPMS if you can't hold on 'til April?

[Kirkhaan]

You are right!

And thanks DavidAlfa for the advice.

Any suggestions for sealing it off again? Now a kind of silicon substance is used.
I guess that's better than using Epoxy or the like, which will become very inflexible.

This might be a good solution to use standard silicon glue:

[DavidAlfa]

Epoxy would do the job great, but opening again would be a total pain.
I would use a poliurethane-based sealer instead silicone. It's more stiff, but not too much.
Or a proper silicone for exterior use. You definitely don't want it to come loose inside....

What worries me more is that silicone will not stick well to a other, dry silicone part.

[Kirkhaan]

Epoxy would do the job great, but opening again would be a total pain.

When I apply the CR2477, it will be OK for coming 10 years I expect (for the original sensors with CR2450 battery, the indication is 6 to 7 years lifetime).

So not being able to open it again would not be a problem. 

[CJay]

Make sure to choose a neutral cure silicone if you go that direction or you may find the cell rattling around inside your tire after the acid eats through the tabs

[Kirkhaan]

I still have a fresh syringe of Bison dual-component Epoxy adhesive laying around:
https://www.bison.net/en/product/epoxy-5-minutes/2266

I think I will use that to seal them. But let me first try how well this sticks to the existing silicon filler!

[Monkeh]

Considering the cost of a replacement sensor and the possibility of needing a programming tool after a battery replacement (I haven't researched that far..), wouldn't it make more sense to just buy the sensor?

[Kirkhaan]

Thanks for bringing this up Monkeh.

I have understood from several vendors of the original sensors which KIA uses, that they are commissioned automatically.
As long as the OEM number is the same as the one that was originally with the car.
The sensors I am going to replace the batteries for where originally with the car, so should be fine.... (?)

So I conclude (hope rightfully) that re-commissioning or programming the sensors is not needed after they lost power (i.e. battery replacement).
They operate at 433 MHz and I guess the "communication protocol" is fixed in hardware inside the sensor.

There might still be a change that it doesn't work, but a new (original) sensor would cost me more than €100.
There are equivalents available (non-OEM) for about €40 per piece. But I am not sure about the compatibility though.
For example:

https://www.ebay.com/itm/TPMS-Tyre-Pressure-Sensor-Kia-Carens-12-20-PRE-CODED-Ready-Fit-/273446658036?hash=item3faab0dff4

or

https://www.amazon.nl/gp/product/B08MTL2KSM/ref=ox_sc_act_title_1?language=en_GB&smid=A2822YNA332XCR&th=1

All in all, for the moment I believe its still worth trying the coin-cell replacement (~ €60 for replacing 4 pieces). Of course having the tires removed again would be annoying....
So if anyone has experience or knowledge about how these sensors commission with the car, then please let me know.

Thanks in advance!

[james_s]

Well, try wiring one up to a pair of AA batteries or some other 3V power source and then hold it in the vicinity of the car and see if the sensor is detected. If it works then you can be confident that properly replacing the batteries will also work.

[amyk]

Frustrating when they're out of stock, I can't help wonder if there's some way to harvest power from the wheel motion and store it to power a TPMS.

TPMS have non-rechargeable batteries that last less than a decade? Feels like planned obolescence... I've never had a car which has one, so I always thought they used some sort of energy harvesting or similar arrangement, given that they don't seem to need much power in the first place.

[CJay]

Frustrating when they're out of stock, I can't help wonder if there's some way to harvest power from the wheel motion and store it to power a TPMS.

TPMS have non-rechargeable batteries that last less than a decade? Feels like planned obolescence... I've never had a car which has one, so I always thought they used some sort of energy harvesting or similar arrangement, given that they don't seem to need much power in the first place.

Nah, TPMS modules are often damaged by tire fitters, heavy bumps in the road, running flat, all sorts of things so they're made to a price and to be replaceable, plus there's plenty of compatibles out there which can be used in place of OEM.

It's  a harsh environment inside a tire, *lots* of vibration, G-forces, high and low temperatures, 10 years is pretty damn impressive.

As for 'comissioning' them, if they're the original ones off the vehicle I reckon it will just be recognised, the ECU/whichever computer deals with them will already know about the 4 or 5 that came with the car and it's unlikely to have forgotten them.

Adding a new one might be more tricky, it may be as simple as the vehicle 'seeing' the new one but I doubt that, I suspect it may be as simple as a certain sequence of buttons/pedal/ignition switch to enter a coding mode or it might require a scan tool to persuade the computer to recognise the new one.

Some (all?) of the clone TPMS modules can be programmed to 'copy' the ID of your original TPMS modules too but that would beg the question why you'd need to if it was still working enough to be cloned...

[Zucca]

I was a TPMS developer for 6 years in a big OEM car company. The TPMS supplier designer are bastards they are counting the life of battery in nvRAM. If it goes close to zero you are required to replace the battery, normally you get the TPMS malfunction warning.

Sure you can replace the battery but the µC will say no no I keep sending the warning message (counter stays below warning limit, even with fresh battery)

This is valid for the TPMS I used to work with, it could be that others are not designed like that.

Batteries in TPMS? I prefer the one I saw without batteries, it never went to production because 10% tires are so different and 90% politics (as always).

TPMS is by definition 100% politics.

[Zucca]

I don't think it will exceed 85C even if you park in the hot sun.

Highest T we measured in high speed tests was about 56C°@32°C ambient, 85? very hard but not impossible.

[Fraser]

Something to be considered when tinkering with these TPMS modules is your car insurance cover. I would expect the TPMS to be considered a safety system by insurance companies. If it is not fitted, fine, but if fitted it should be fully operational to warn the driver of a potential partial deflation and blowout risk. If a TPMS sensor is tinkered with, no matter how well the work is carried out, it might present an insurance company with the ability to invalidate your insurance if you suffer an accident due to a tyre blowout. Just food for thought.

As has already been stated, it is common these days for devices in cars to be married to the associated processor module. New parts are often provided in what is called promiscuous state that the controller recognises and automatically marries to. The sensor then sets itself to non promiscuous mode and this is not normally reversible.
If, as has been stated, the TPMS system uses a countdown to EOL, that mirrors other safety systems such as heart starter Defibrillator batteries that have a built in electronic expiry algorithm for reasons of safety. If the TPMS has such a system, it would need to be reset if a new cell was fitted. If such is possible, it is usually detailed on the internet, as with printer cartridge resetting.

My experience of working on my 2005 Audi is that there are many modules married to the car that require a dealer system to access the OBD II port to reset or marry them to the cars systems. As stated, new parts are promiscuous, but used parts require a manual marrying process. I use VAGCOM for such work on my Audi but it would be worth some digging on the internet to discover how TPMS sensors are married to their controller and whether software for such acting via the OBD II port is needed.

Fraser