Iot SensorV2 with battery onboard

Esp8266

Iot SensorV2 with battery onboard

Not a complete new design, but a redesign of my Iot Esp8266 sensor V2, the schematic is exact the same however this time with a on board 18650 3.7V Li-ion battery.

The Iot sensor node will measure temperature, humidity, atmospheric pressure and light. The light is measured with the TSL2561 and temperature, humidity, atmospheric pressure with the Bosch BME280.

In the previous design the battery was placed in a separate battery holder and the pcb was taped to the battery, not really the ideal solution. So the idea was born to combine everything on 1 pcb.
The first idea was to place the battery beside the electronics, when this was finished I thought that can be smaller and made also a design where the pcb is on top of the battery. Still I couldn’t decide if I wanted the side or top version. Ok, lets combine both designs and we will see later what’s version is nicer.
Just as mentioned in then previous design, it’s very hard to solder the BM280. My opinion is that you only can solder it good if you use a stencil to apply the solder paste and place the pcb in the oven or use a hot air station.
For the battery clips I used the Keystone 16~19mm PC Battery clip. In the datasheet they note that for an 18650 with build in protection circuit you need 48mm between the front solder pins, that will make it fit for battery’s of 68mm if you add the rest of the clip. However I don’t think this is correct, at least not in my case. 18650 battery with build in protection are 69,7 mm long, it will fit but it looks that it’s way to tight. For 18650 battery with flat head the clips are to far apart and won’t make contact. An 18650 with button head will fit perfect. If you want to make your own sensor node, keep in mind that there are a lot of different sizes 18650.
I’m using now the Sanyo NCR18650GA 3350mAh – 10A Button Top and that fits perfect, they are 66.7mm long (battery used on the photo’s is not the Sanyo).