I’d like to monitor the general temperature and humidity in my greenhouse, I have an emonTH which should be in range of the base station from the greenhouse. Should I be concerned about the emonTH getting too hot, especially the NiMH batteries inside (Panasonic Eneloop)?
http://batteryuniversity.com might give you (impartial) data about the batteries. The emonTH data is in Resources, you’ll probably need to check the data sheets for the individual parts. From memory, it should be good to 70°C (but I’m open to correction on that).
Sorry, a bit late replying. I had an EmonTH in a greenhouse for two years, no problem with rechargeable batteries, but the humidity killed it. Some faint corrosion appeared on the PCB, and I could never get it clean enough to make it stable, so replaced it with an old Oregon Scientific weather sensor. I’m picking up the sensor via an RFlink board. I’d suggest some conformal coating on your PCB before use.
I’ve had a emonTH in my greenhouse for over 2 years now, including through the winters, and still working fine with no signs of corrosion (I’ve just checked). I just ensure that I don’t drench it whilst watering!
I am not using rechargeable batteries though, but I did modify the firmware to update less frequently.
NOTE; I’m still using the same set of batteries!!