I've been checking the forum and Google but still haven't got precise solution to my current question. In short, we are looking for rechargable batteries for Arduino that survive under -40 Cenlcius Degree.
Our group is going to deploy several sensors in the Polar Region, Arctic, to study the permofrost. These sensors disperse in the area around a community, within some kilometers. The data collected by the sensors are to be saved with Arduino-based nodes, and then uploaded to cloud for quasi real time. Hence, the Arduino modules serve as dataloggers and LoRa nodes. In the community, we've got power line to power up the LoRa bridge. But all the end nodes out of community cannot access AC power source.
Lacking of poewr supply, the end nodes rely on batteries and solar panels. There are several considerations here. For example, sensing and LoRa transmission need to be set to very low frequency, like, once per 15 minutes, to reduce the power consumption. We would set it via programming, and set Arduino to sleeping mode for the rest of the time.
Here comes the question I'm not pretty sure: what kind of battery and solar panel should we use? The temperature at site is super low, going to -40 celsius degree in deep winter. Most common used battery cannot survive this temperature. We also need the battery to be rechargable, which could be charged with solar panel (of course ,mostly during Spring to Fall while there is sunshine). Our technician used Lead Acid battery in the past but the performance was very marginal: the batteries of some sites were severely damaged and even broken during winter.
And solar panel and power source regulator? It is our plan to decrease the working time to the most so we could reduce the size and cost of solar cells, but still, we need them to stay alive.
As a Canadian who has worked in Yellowknife NWT, I can understand your problem. No rechargeable battery is going to work well at -40. Battery performance drops and a discharged battery can freeze. That being said, NiCads are a good bet as they only drop to about 20% capacity at -40. It's also important to include low voltage cut out circuitry to avoid the risk of freezing batteries.
Another important consideration is the temperature rating of the electronics. Are all your components rated for -40? You must use military spec'd parts, if you expect to run reliably at that temperature. This is an expensive requirement, but for the harsh Arctic environment, it is not optional.
I have not been to the Arctic, not researched such things. But, did you ask the locals what battery they use in their snow machines?
You are using the air temperature to look for a battery to survive it. Since you are researching permafrost, find a battery that will work at that temperature. Dig a hole and bury the battery.
betaarduino:
For example, sensing and LoRa transmission need to be set to very low frequency, like, once per 15 minutes, to reduce the power consumption. We would set it via programming, and set Arduino to sleeping mode for the rest of the time.
So what is the power consumption, in mAhr, of the entire node going to be per day ?
From website- https://www.saftbatteries.com
Saft battery systems - key features
robust, lightweight Sintered/Plastic Bonded Electrode (S/PBE) construction
special electrolyte developed to ensure optimum performance in extremely cold conditions
operation at temperatures down to - 40°C
survives prolonged exposure to temperatures as low as - 50°C without damage