TPMS battery replacement

Have 4x TPMS from my 2011 Prius from replacement 2 years ago (1 died) Kept them and recently helping a foreign exchange college student maintaining her 08 Lexus RX350 @ 212k miles with the 2GR-FE engine. Car has 3 older sensors (including the spare) and 1 died. 2 others were replaced by tire shop.

New sensors are Denso 550-0103 ($41 on Amazon, $37+ship on rockauto) These were the replacement I purchased for my Prius. Exact match. Made by Pacific Industries just like the OEM. Costco programmed my new ones but I could have done it with Techstream as well.

Trying to save the student some $ so decided to look into battery replacement. Here is the info so far

Digging out the old battery

After prying the rear cover off. Scraped off some sealant and liberated the battery. Need a thin blade (like exacto knife) to separate the battery from the welded on tabs.

Many people just solder the new battery tab onto the old tab. I wanted to see how difficult to remove the old tab to leave a nice hole to solder new battery tab to. Gobs of solder need to be wicked off the old tab. Tabs also insert from the bottom of the board so clipped off tab extruding from top of the board. Wife held the TPMS, apply flux, solder and pull with needle nose to liberate the tabs from bottom of the board. Tiny surface mount components are not too far behind (even got a tiny ball of solder on one) so need to be careful.



Replacements

Exact replacement on Mouser (Digikey required min 200 quantity) for $4+ and $9 ship. These Panasonic batteries are due to obsolete on 6/30/26

https://www.mouser.com/ProductDetail/658-BR-2450A-FJN
https://4donline.ihs.com/images/VipMasterIC/IC/PANA/PANA-S-A0006259314/PANA-S-A0008380763-1.pdf?hkey=CECEF36DEECDED6468708AAF2E19C0C6

TPMS casing has molded ridges and tabs that clips onto this exact battery. Another 2450 (24.5mm) likely won't clip in perfectly and more reliant on sealant for structural support.

Replacement battery tabs inserts from the top of the board which makes it easy to solder on. Tab length and measured distance on the TPMS seems to be a perfect fit (see drawing on mouser link and measured distance in pic)



On the mouser battery mechanical drawing, top left is looking from bottom of battery and top right is from top. So the polarity of the tabs are correctly matched to the TPMS board battery tab holes.

Weight

Weight is quite close. Lightest stick-on wheel balance weight segment is 1/4oz so should be no problem leaving the black backing plastic off (new ones I bought didn't have them. Just transparent sealant) I'd prefer not to reinsert the plastic plate back onto a compromised lock on the TPMS shell and worry about them coming off. I guess certainly can melt the lock once back plate is on. But seems unnecessary as new ones don't have the backing plate.



Results

Need to order replacement battery. Will report back.

A lot of work but save ~$40 x 4 or 5 for cars that have a spare. A key challenge is unless you know the exact battery shape and how it's held in the shell, can't order in advance. I suppose other 2450 lithium batteries with tabs can work. It would probably depend more on the sealant for structural support rather than just moisture seal.

Since the Panasonic BR-2450A/FJN battery is becoming obsolete. Maybe the new compatible Denso TPMS might have slightly different battery clip shape under the sealant to fit newer batteries. Just speculating.