My Dad, Touringon2, and I have been using the Doran TPMS on our bikes for a handful of years now and are very happy with the system. I had to replace the sensors a few years ago due to dead batteries, and at that time they were $25 each. Well this year I had to replace the sensors, and they were $35 each (they've been delivered already), and I was told that in the near future, the sensors were going to be $45 each. With shipping, that would come out to about $100 every few years to replace the sensors, and that started to bug me a little bit. I knew there had to be a way of replacing the battery in the sensor. It was just a matter of how to get it out. Well, over the last few weeks I set out to do just that, and I'm happy to say that I've done it !
I wanted to start this thread to help anybody else who likes working on their own things and also uses a Doran system as it will save quite a bit of money in the upcoming years by being able to change the batteries in your sensors for around $5.
Changing the batteries is not hard, but there are certain steps you have to take the first time in order to prevent damaging the sensor inside, so each step of the way I snapped a picture to illustrate how to remove the battery without damaging anything.
My first step was to preheat the oven to 325°. What fun would a job like this be unless somehow you could incorporate your wife's oven to get it done! Once the oven was heated, I set the sensor on a block of wood in the oven and left it there for 10 minutes. Next I took the sensor out, put it on the workbench, and carefully wedged a razor blade into the sensor right along the seam where the top was molded on to the rest of the sensor body. When doing this, try to follow the seam as closely as possible because you want the two surfaces to be able to mate up later when you glue them back together. I would even suggest taking a magic marker and drawing a line at the edge of the top and then down the side of the sensor so you can glue them back together in the same orientation they came apart. Once you get the top cut off, here is what you are looking at.
Yup...there's the battery looking right back at you. Nothing special, and not encapsulated with a mystical gel or epoxy.
The next step is to pry that metal strip off the top of the battery. They manufacture these batteries with the strips tac welded or something right from the factory, and those two little spot welds really hold on well!
I put the razor blade under the front edge of the strip first and bent it up just a little bit. Then using a knife or in my case an old continuity tester with a good point on it, get under the strip and pry it off the battery. It will take a decent amount of prying, because like I said, those little tack welds really hold. Once you get the first tac weld off then work your way to the second. Just hold the battery down in the center with your thumb. You don't want to lift the battery up before the spot weld is broken, or you could pull the strip off of the sensor's circuit board. It is just soldered to the circuit board sitting under the battery.
Once you get both spot welds separated from the battery, bend that metal strip straight up. This next step is very important in not damaging anything in the sensor!!!! You now have to do the same procedure on the bottom side of the battery. There is a second strip tac welded to the bottom to make contact with the negative side of the battery. When lifting the battery up, it is very important to lift it right where it touches the strip that you just bent up!!! The strip under the battery is soldered to the circuit board directly opposite the side you just pried up. If you try lifting from that side of the battery, you will break the solder from the lower strip off of the circuit board. Lift the battery up just enough so you can see underneath of it. You will see a thin plastic film on the bottom side of the battery. Suppliers send the batteries with this film on them. The metal strip you are going to remove under the battery is between that blue plastic and the battery itself. So using a razor just scrape that blue plastic off of the battery. I'm not sure if the plastic is supposed to be an isolator between the battery and the circuit board, so I did save it for later installation.
Once you scrape the plastic off of the battery, use the same procedure to break the small welds from the bottom of the battery, starting with the weld in the center of the battery, then the one closer to the edge of the sensor.
When the lower strip has been removed from the battery, the hard part is over, and you will never have to do that again! The batteries we will be installing don't have those small welds on them. With the battery removed, here is what you are looking at.
Looking at this next picture, you can see why it is important to lift the battery the way we did in order to avoid breaking the solder. The metal strip is attached very well, and will take some force, but if you tear the strip from the circuit board, I would think the sensor is scrapped unless you can re solder it.
Now it is time to simply put your new battery in and glue the top back on (don't forget to slide that piece of blue plastic back under that lower tab so it sits on to of the circuit board just in case). The battery that is used is a very common 2032 battery which is available at most stores. I did just a little research online and even though all of the 2032 batteries were 3V, the Energizer had the highest rated mah, so that's what I decided to use. I bought mine from autozone for around $6 for both of them. I know you can get them much cheaper from Amazon or elsewhere, but I wanted mine right now.
The hardest part of this whole process for me was finding an adhesive that would seal the top back on and hold under pressure. I first tried black silicone, and it leaked immediately when I screw the sensor on. Next I tried a gel made by Loctite, and it lasted for about 15 seconds after I screwed the sensor on the tire. I then spoke to friends of mine at a machine shop and they handed me a bottle of glue and said, "Here, take this. I guarantee this will work."
Well, they were right! This stuff is like super glue on steroids! I put a small bead along the base of the sensor and then pressed the cap down. It held immediately, but not wanting to take any chances, I clamped the sensor in the vise and left it there for 24 hours just to make sure it set up. Even though it sets up in a few seconds, it does say on the bottle it is fully cured in 24 hours.
There is one option in gluing the top on that worked both ways for me. You can either glue it on in the same orientation you cut it off, or, put a piece of sandpaper on a flat surface and sand both the top and the sensor body so they are both flat. Ultimately that is what I did. Just use caution when sanding the body so you don't break the upper tab which will be sticking out a little.
Here's a side note to the story. When I did the first sensor, it worked perfectly. The next day I changed batteries in the second sensor and glued the top on. When I put that sensor on my bike, it was not working. I was afraid I damaged one of the strips while disassembling it even though I was careful when taking it apart. The good part about this story is I got to see how strong the glue was and if I would ever be able to take the top off when needing to replace these batteries. I put the sensor in the oven and took the top off the same way I did originally. The glue held about as well as the original bond was, but you are able to take the top off in the future if needed. Once the top was off, I removed the battery and made sure there was continuity between the two contacts, and there was. At that point I knew I did not break either of the soldering points. The only other thing I could think of at that point would be a dead battery, but I just purchased the batteries a few days ago and it said on the package they were good until 2022. I then put the leads from my multi meter on each side the of battery and it showed 1.5 volts. It was brand new and dead right out of the package. Moral of the story.....check the batteries before installing them even if they are brand new ! So back up to Autozone I went, and picked up another battery. When I got home, I checked this one and it showed 3.2 volts. Perfect! I glued the sensor back together clamped it in the vise over night, and today......It worked !
Next I will be sending my brand new sensors back to Doran since I never used them, and in the future, I'll just be changing my own batteries (and my Dad's).
Also, I did ride the bike about 100 miles with the first sensor just too make sure there were no issues with the glue. That stuff is awesome and it held with no problem. The tire has maintained pressure for the past several days, so there are no leaks.
I did a Google search for the glue, and you can buy it for $20 a bottle.
I found it at this website.
Hopefully you can just click on this link and go directly there.
Please add a link if you find it cheaper somewhere.
That bottle will do a lifetime of sensors....It doesn't take much glue to put the top back on.
Here are a couple of close up pictures of the stock battery. You can see how well the tiny spot welds (or whatever they are) held.
I hope this helps some of you with the Doran system. It's really quite easy, and I'm happy now that my Dad and I are done buying (what I believeto be) over priced sensors !
Edit : I added post #9 below after posting this. Please be sure and read that post before installing your battery !