What are your recommendations for methods or devices that are neither complex nor expensive to keep batteries warm and cool in a harsh (hot/cold/moist/dusty) environment, to ensure long cell life?
I'm designing a small solar-powered camera product and I have my choice of battery types: lithium, lead, nickel, etc. The camera would sleep most of the time so for average hourly use I estimate around 10mA x 12V (120mW). The environment could be very dusty, humid, hot, or cold. I cannot require constant maintenance, so a fan with filter does not seem to be a good idea. I can go with a larger pack to reduce the charge/discharge rate, if that is necessary.
Since this is for the outdoors and the initial sales would be in the United States, I expect ambient charging temperatures to be between -18°C/0°F in the winter and 38°C/100°F in the summer. Discharge temperatures could be as low as -34°C/-30°F in the winter and 38°C/100°F in the summer. Humidity can be as much as 100% but 87% is more typical in locations like Florida or Louisiana.
I was asked to supply the following info:
- How your device looks: Imagine a security camera with a solar panel.
- What it might cost: Less than USD $100 with parts cost less than $50 would be ideal. Any more than that and I might not consider creating the product.
- What amount of field failure you can tolerate: Not sure how to quantify this. A life of 5 years would be fantastic. No less than 3 years.
- Where it's going to be mounted by whom: Eaves, trees, walls, by non-trained personnel e.g. homeowners, farmers.
- How heavy it might become: Small device, so about 1-2kg/2-4lb.
Is this even a concern? On my house I have these solar-powered security lights that have no heating or cooling. Just Ni-Cd batteries in a black plastic enclosure. I live in a climate with hot summers and cool winters. The devices are mounted in the sun and have been going strong for years. I see from reviews on those devices that they are installed in both very cold and very hot locations, and perform admirably. Yet the typically-recommended charge/discharge temperatures for Ni-Cd cells is 0°C to 45°C and -20°C to 65°C, respectively. Cells in an uninsulated black plastic box exposed to sun and snow surely must reach temperatures outside of that range, right?
And there are solar-powered trail cameras that hunters use in cold and hot weather.
Am I over-thinking this? Should I just drop some Ni-Cds in a black plastic enclosure and be done with it? Or are there some inexpensive temperature management solutions?