### Run on battery & solar panel#71691

By liderbug
#71691 A project - rural mailbox - when the door is opened (mail's here) gpio pin X goes high, 8266 sends sms to phone.
A. How much solar panel is needed to keep ~3.3v battery (5v+3.3reg)? (I hate reinventing the wheel...).
B. What is the range of a 8266? 50ft? 100? 500?
a. can an external antenna be attached?

Tks

### Re: Run on battery & solar panel#71694

By liderbug
#71694 And with that I answered my own question:

4.2 km - my mailbox is ??? 30m

### Re: Run on battery & solar panel#71698

By philbowles
#71698
liderbug wrote:And with that I answered my own question:

4.2 km - my mailbox is ??? 30m

...on a good day with no solar flares, miles from any power lines, direct line of sight, no other WiFi in hearing distance, your router in a paper house and several planets lining up...

Look at the Wemos Pro or any other dev board with an external antenna connector and get a decent aerial.

I'm looking at solar for some of my outside projects...The main thing is the battery type and how much sun you get. You'll need to do some basic maths - if you are "always on" at roughly 70ma typical usage, a 7AH battery (e.g. small motorcycle type) will last you 100hrs - that's ignoring any losses from stepping down from 12v, which will be significant, so (just a guess) say 3 days. Depending on how much sun you get in the winter, the output / efficiency / voltage / step down topology of your charge controller etc etc it MAY be enough to keep it "topped-up". If you are going to go down the "low power sleep/wake up and send" route, then significantly longer...

There are a LOT of variables, its a very difficult question to answer precisely. I'd be interested myself in any real-life examples any other readers have.

### Re: Run on battery & solar panel#71701

By rudy
#71701 Also consider that if using up all the battery's charge (deep discharge) as a normal situation it will shorten the battery's life.