TPMS battery replacement - Maxell CR2450HR EX battery - Page 1
Forum section: electronics / general

author: Kirkhaan
author_rank: Frequent Contributor
timestamp: February 27, 2021, 08:15:23 pm
content: 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.pdfThe 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!

author: CJay
author_rank: Super Contributor
timestamp: February 27, 2021, 09:02:44 pm
content: https://uk.rs-online.com/web/c/batteries-chargers/non-rechargeable-batteries/button-batteries/?searchTerm=cr2450&applied-dimensions=4294819682Or does it have to be that exact part?

author: Kirkhaan
author_rank: Frequent Contributor
timestamp: February 27, 2021, 09:11:19 pm
content: 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.

author: amyk
author_rank: Super Contributor
timestamp: February 27, 2021, 10:24:11 pm
content: I suspect an 85C battery will work fine, but simply not last as long if indeed the environment temperature goes up there.

author: james_s
author_rank: Super Contributor
timestamp: February 27, 2021, 10:32:17 pm
content: 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.

author: bingo600
author_rank: Super Contributor
timestamp: February 28, 2021, 07:28:07 am
content: What KIA ??Take & post some pics of the TPMS , and where it's mounted etc ....Curious about the build up/Bingo

author: Kirkhaan
author_rank: Frequent Contributor
timestamp: February 28, 2021, 07:50:47 am
content: Quote from: james_s on February 27, 2021, 10:32:17 pmWell, 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.

author: Kirkhaan
author_rank: Frequent Contributor
timestamp: February 28, 2021, 07:53:04 am
content: 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.

author: CJay
author_rank: Super Contributor
timestamp: February 28, 2021, 10:07:30 am
content: Quote from: Kirkhaan on February 27, 2021, 09:11:19 pmI 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 friendhttps://nl.farnell.com/murata/cr2450w-ho5/battery-li-manganese-dioxide-3v/dp/3408811?ost=cr2450w-ho5

author: Kirkhaan
author_rank: Frequent Contributor
timestamp: February 28, 2021, 11:14:52 am
content: 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/

author: DavidAlfa
author_rank: Super Contributor
timestamp: February 28, 2021, 11:25:32 am
content: 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:

author: CJay
author_rank: Super Contributor
timestamp: February 28, 2021, 11:42:18 am
content: Quote from: Kirkhaan on February 28, 2021, 11:14:52 amFrustrating 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?

author: Kirkhaan
author_rank: Frequent Contributor
timestamp: February 28, 2021, 11:46:32 am
content: 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:

author: DavidAlfa
author_rank: Super Contributor
timestamp: February 28, 2021, 11:49:05 am
content: 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.

author: Kirkhaan
author_rank: Frequent Contributor
timestamp: February 28, 2021, 01:11:42 pm
content: Quote from: DavidAlfa on February 28, 2021, 11:49:05 amWhen I apply the CR2477, it will be OK for coming 10 years I expect (for the original sensors with CR2450battery, the indication is 6 to 7 years lifetime).So not being able to open it again would not be a problem.

author: CJay
author_rank: Super Contributor
timestamp: February 28, 2021, 01:43:13 pm
content: 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

author: Kirkhaan
author_rank: Frequent Contributor
timestamp: February 28, 2021, 07:22:52 pm
content: I still have a fresh syringe of Bison dual-component Epoxy adhesive laying around:https://www.bison.net/en/product/epoxy-5-minutes/2266I think I will use that to seal them. But let me first try how well this sticks to the existing silicon filler!

author: Monkeh
author_rank: Super Contributor
timestamp: February 28, 2021, 07:30:11 pm
content: 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?

author: Kirkhaan
author_rank: Frequent Contributor
timestamp: February 28, 2021, 07:46:04 pm
content: 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=item3faab0dff4orhttps://www.amazon.nl/gp/product/B08MTL2KSM/ref=ox_sc_act_title_1?language=en_GB&smid=A2822YNA332XCR&th=1All 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!

author: james_s
author_rank: Super Contributor
timestamp: March 03, 2021, 03:00:00 am
content: 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.

author: amyk
author_rank: Super Contributor
timestamp: March 04, 2021, 02:43:58 am
content: Quote from: CJay on February 28, 2021, 11:42:18 amTPMS 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.

author: CJay
author_rank: Super Contributor
timestamp: March 04, 2021, 08:56:33 am
content: Quote from: amyk on March 04, 2021, 02:43:58 amNah, 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...

author: Zucca
author_rank: Unknown
timestamp: March 04, 2021, 10:07:26 am
content: 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.

author: Zucca
author_rank: Unknown
timestamp: March 04, 2021, 10:13:34 am
content: Quote from: james_s on February 27, 2021, 10:32:17 pmHighest T we measured in high speed tests was about 56C°@32°C ambient, 85? very hard but not impossible.

author: Fraser
author_rank: Super Contributor
timestamp: March 04, 2021, 02:13:43 pm
content: 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

author: Zucca
author_rank: Unknown
timestamp: March 04, 2021, 04:09:39 pm
content: TPMS and safety?There are two tire families: regular and run flat.Regular: better on gas mileage, in case of puncture you need to stop the journey immediately with the risk of loosing control of vehicle (TPMS does help but does not solve the problem at all here)Run flat : tire shoulders are reinforced, in case of puncture you still have 100Km or so to reach the tire shop at low speed. They offers much better handling in case of failure. There is no free lunch, it requires more energy to rotate that tire on the road (bad gas mileage).Problem is a low leak (or even a high leak sometime, if the driver is a old lady) in a RF tire is not necessary noticeable by the driver --> danger --> TPMS required by law.What also push the TPMS law was the CO2 emission. If you ever tried a flat tires bike, you know how much tire pressure is important on energy efficiency. TPMS will warn you not only if your tire is leaking but also if it is low on pressure --> that's why in winter with low T a lots of bing "check tire pressure" warning are displayed on cars.Please note:- every 10C it means about 0,1 bar variation in the tires.- a perfet tire with no damages loose about 1 bar/year since it is not a perfect sealed system. (we call it diffusion)you are smart enough to understand the consequences.Regarding pairing, a good TPMS should recognize a new set of wheels without any extra tool. In our system we had 8 position in memory for the tires, 4 for sommer and 4 for winter tires for quick detection. If the set was not in memory it took only longer to get accepted by the ECU. You should do a TPMS reset anyway in case of changing tire, should be RTFM.

author: DavidAlfa
author_rank: Super Contributor
timestamp: March 05, 2021, 10:29:10 am
content: "A good TPMS should..." What?.Remember that the brand usually fu**s it up the most possible to force you going to thedealerstealer and stab you in the liver.

author: coppercone2
author_rank: Super Contributor
timestamp: March 07, 2021, 10:03:39 pm
content: I just soldered a 2450 by leaving it in the freezer then soldering one side and then putting it back into the freezer and soldering the other side afters its cold and then putting it back into the freezer. the voltage looks OK but I have no idea what damage I caused.it is for a coin cell backup inside of something in a thick box that I don't really care about too much so I think it will be ok.

author: Zucca
author_rank: Unknown
timestamp: March 07, 2021, 10:30:54 pm
content: Quote from: DavidAlfa on March 05, 2021, 10:29:10 amNot the one I designed between 2006 and 2011.

author: coppercone2
author_rank: Super Contributor
timestamp: March 08, 2021, 12:25:30 am
content: my coin cell has been in circuit on a RTC for a few hours now after soldering and there is no explosion or nothingI watched a youtube video on heating a coin cell, he used good solder contact on a big iron for 1 minute before it popped, my solder operation took maybe 3 seconds, you can do it with less also if you scrape it a little bit to activate the metal. I think it will be fine for a while. I don't know if pre-cooling helps or hurts.On a normal power battery this is a bad idea because it has high surge current, but on a RTC its practically nothing, I don't think its being degraded alot. I think so long its in a metal enclosure you are OK.

author: Fraser
author_rank: Super Contributor
timestamp: March 08, 2021, 02:42:57 am
content: The issue with soldering button cells is that of melting the plastic seal between the positive shell and the negative contact. Any damage to that seal is a possible cause of cell leakage and all that such entails. Explosion of the cell is not normally a risk if the heat is not applied for an excessive period of time. There is also concern about the effect of the high temperature at the contact surface on the internal materials. Excessive heat can degrade those chemicals in the locality of the 'hot spot'The spot welding of tabs onto cells is the traditional method of 'hard wiring' them into a circuit. The spot welding process does generate localised heat in the casing metals but such is not normally enough to do any harm. Direct soldering is frowned upon by the cell manufacturers and this is understandable as some people may not prepare the surfaces and solder to them quickly enough to avoid damage to the cell.IMHO, with battery tab welders from China now costing less than £20 in the UK, it is well worth spot welding nickel strips to cells and avoid direct soldering and the issues that can result. The Mini Welder is discussed on this forum. If you want a better battery tab welder, then the KWeld is a good choice. I bought a Mini Welder to play with and, after some important modifications, it works very well off of a 12V car battery.Fraser

author: DavidAlfa
author_rank: Super Contributor
timestamp: March 08, 2021, 11:40:23 am
content: I tried that years ago.After 2-3 seconds, when the solder began to stick to the surface, the battery started leaking and bubbling.I never tried again, bought batteries with soldered tabs when needed.

author: oasis2020
author_rank: Newbie
timestamp: December 22, 2022, 03:48:41 am
content: Soldering the battery with a soldering iron requires acidic flux.Clean the welding surface well and use the least time for welding. I do it all the time, nothing out of the ordinary.