Where do you get a tiny, high capacity battery that is 12v?
How do I recharge that with a solar panel? And, is it 30000mAh like the 5v powerbank I am using?
Let me take that back 
IMO suggest you use your battery pack and add a Boost Converter like the one offered previously.
I have found they work well.
1 Like
Sorry, I hadn't told you what my specs were.
Ok, I'll go with a boost converter then. My only worry is that the boost converter may get hot and make my temperature sensor incorrect.
They run cool 
1 Like
Oh, awesome!
You're worried about low power consumption of your controller, but most powerbanks require a minimum current just to stay on. Does yours do that? And will it let you power your device while you're charging it?
What do you have in mind for a solar charging circuit?
This one requires a minimum current of 100mA... Maybe I shouldn't worry about a low powered arduino with it 
At 110mA I'd still last 11 days, so not even a huge issue I guess!
Just a 5v solar panel and this
I just spoke to the manufacturer - yes you can charge it while using it to power other devices.
@ShermanP
Maybe I'll do this:
With my board in low power mode it would last for 58 days. I still need to measure the modules I haven't got yet - after I buy them. Maybe I'll get 20 days without recharging.
I don't know anything about those products. Perhaps someone with more experience in solar charging can help.
I’ve used these for a 18650 battery.
Could I hook up 4 18650 batteries?
I’ve only charged one.
Is there any way to get AC power to the housing ?
No. It is sort of like a "field" instrument.
What is the ambient temperature range where you live ?
On the rare occasion it might get down to 0ºC, but usually 5ºC - 40ºC (outdoors). That's normally. Sometimes lower, and sometimes higher.
@LarryD
Why do you ask?
Some batteries do not take kindly to extreme temperatures i.e. too hot or too cold.
There capacities are reduced and or they can be damaged.
1 Like