Sonoff SNZB-02 to CR123A battery

thingiverse

**Warning:** *When connecting batteries in parallel check your connections carefully. An incorrect setup can cause batteries to overheat and possibly explode. Do not mix battery type or voltage, as this can also lead to major problems. If the batteries are not the same voltage (one is drained more than the other) the higher voltage one will try to charge the lower voltage battery which can overheat and damage the batteries. If you do install 2 batteries and you feel one heating up, remove it. Chances are that the batteries are not equal voltage and are trying to balance their charges. If you are unsure, its probably better to just run with a single battery. One CR123A battery appears to last quite a bit longer than the CR2450s. Use at your own risk. * **Updates:** *2024-02-25* I finally go around to printing and soldering together a new 2-Battery unit to replace the CR2450 for my back yard sensor. Around December the original battery died so I replaced it with another new battery. It has lasted for a couple of months and has demonstrated the same discharge and disconnect behaviours as the previous battery I installed. In the meanwhile my single battery CR123A replacement has maintained about 60% battery life through some very cold stretches for here (-12C) The other day, the 2nd new CR2450 battery I installed dropped to about 2% again so I decided to go ahead and connect it to a double CR123A. Before putting the batteries into the new case I checked their voltages and they both read 3.1v I have it up and running now and it will be interesting to see how long it will maintain a battery charge with two CR123A batteries. *2023-12-07* I finally got a bag of battery terminal ends from AliExpress that cost a couple of dollars and decided that I should make the case fit them a little better. I assume that the size is pretty standard. The width is about 10mm and the height of the rectangular part is about 9mm, 16mm including the solder tang. I have uploaded a V2 of the casing that fits these parts tightly. If they are too tight probably heating the piece and then pushing it in place with some needle nose pliers would work. Of course you can still use the old version but the clip might be a little loose unless you apply a bit of hot melt glue or something similar. *2023-11-24* When I made the new enclosure I installed new batteries into both my outdoor temperature sensors. Since then (over the last 2 months) the battery levels have dropped in both devices. The original CR2450 has died twice in the last 2 weeks. I lost signal and the battery level reported 2%. I brought it inside a re-paired and eventually the battery began to report about 40%. It worked for another 2 weeks then died again. This time the battery reported 3%. The updated CR123A (single battery has dropped to about 65% and continues to work properly. When I get the opportunity I will print another box and this time use 2 CR123A batteries. Because these devices require battery changes I designed and printed two simple mounts that hold both the original TH01 and the slightly larger case which I am calling the SNZB-02 Mount. They have a screw hole in the back to fasten to a wall and the the sensor just sits in the holder, allowing easy removal for battery replacement. I can also print and position several mounts and it makes it easy to place the sensor in different locations if necessary. My other issues of humidity and temperature calibration were resolved by calibrating them within HomeAssistant by creating Zigbee Helper Templates. **Summary:** I was having problems with my Sonoff SNZB-02 temperature sensor that I use outside. The battery would never last long and then it would disconnect. I decided to try and use a larger capacity battery and since I had a few CR123A batteries lying around opted to go that route. I disassembled the Sonoff down to the board and soldered two leads onto the positive and negative terminals on the board. I designed the case to hold the board and two CR123A batteries even though I was only going to use one. To use the second battery the existing Positive battery terminal would either have to be removed or it could be folded flat against the board. If you do use two batteries make sure they are wired in Parallel and not in Series to ensure you only have 3V. If you wire incorrectly you will probably fry your board. I had a couple of metal battery clips that I had removed from an old baby toy and used those for my battery terminals which I soldered to the power leads. I don't think it would be too difficult to make a couple of pieces out of scrap, or you can buy them on line. I just left slots to mount the end terminals, so they are friction fit or could be glued in. The case itself is slightly larger (length x width) than the original Sonoff case but is about twice the depth to accommodate the larger battery. I put a couple of holes in the lid so it could be screwed onto the base. The base holes will need to be drilled. I found that the lid was a very tight fit using a 0.6 nozzle and I actually had to sand down the parts to allow it to fit on properly. Mine fits tightly without any mechanical fasteners. Don't forget to put the button in place before putting in the board and battery and make sure it moves smoothly. I have the device running now hoping to see if I can tell if it will make any difference. The one strange thing that I do see is that the humidity appears to be reading too high. The temp appears to be working properly but I'm not sure if there will be any difference in temp reporting due to the larger battery. I don't know if these larger batteries produce more heat than the coin batteries and/or if this would have any impact on the temperature reporting. The humidity sensor is reporting quite a high relative humidity which I don't believe is correct. I'll have to move the sensor to a new location to see if it will change. I'm hoping I didn't damage the sensor when I was handling it. I compared to some other sensors and the humidity is reading about 30% higher than the other sensors. I'll have to see if its a setting that I can adjust in software. The humidity difference could just be the different devices. I compared my SNZB-02 to my SNZB-02D where the RH% was showing a 20-30% difference. My other SNZB-02s are all about the same so I should probably try and calibrate them all properly before worrying about this one device. The only reason I use the relative humidity would be for my filament dryer and printer area but I use different devices for those.