A few months ago, Andreas presented a nice version of the “throwie” (a LED packed with a small battery that you can throw & see shining for hours) using an ESP8266 instead of a LED : a “wifi throwie”.
He could not make it work with button cell batteries (the ESP8266 draws too much current) so he ended using a 3.7 LIPO battery, which is quite bulky as you can see on the following post : http://hackaday.com/2015/05/03/esp8266-wifi-throwies/
What if you could use instead a cheap mini drone battery you can find for half a euro on eBay ?
Bingo !
Introducing the “wifi throwie 2.0”, using a micro 100 mah lipo battery recycled from a broken minidrone. According to espressif data (http://bbs.espressif.com/viewtopic.php?t=133), the ESP only burns 15 ma in “Modem sleep mode” – which can last 6 hours with a 100 mah battery. Since the server only send a 5k picture (takes less 30 seconds at 120 mah, ie 1 mah), you can serve ~ 100 connections before the battery dies. The number if even larger if you only want people to see the AP name, but not to really connect.
[Edit] :
-As seen in hackaday !
-I tested the battery with a programm connecting to the internet, sending a tweet and waiting for one minute. It could stay alive 2 hours and a half and send 160 tweets before dying… More than enough for many applications…
You’ll find here a demo : https://www.youtube.com/watch?v=nD_AHmZ63PY
The throwie appears as “ggo iot demo” hotspot. One connected to this hotspot, any url leads you to the captive intraweb showing an “iot demo” picture.
Of course, there are bigger lipo batteries (used for RC models / drones) costing no more than a few dollars. For example this one costs 2 $ and offers a 500 mah capacity: http://www.ebay.com/itm/3-7V-500mAh-Li-Po-Battery-For-Hubsan-X4-H107-H107L-H107C-H107D-V252-JXD385-HC-/281790908597?hash=item419c0c08b5:g:t0QAAOSwqv9V6ToU
For more detail: Wifi throwie : improved version
