ESP8266 Community Forum

- Tue Jan 12, 2016 3:21 pm #38617 Hi,
I have successfully setup a NodeMCU development board so that it sends a reading of a sensor every few minutes and in between goes into deep sleep. Now I want to make it battery powered. I tried two options. One being a cellphone battery pack and one being a battery pack with a solar panel. It works until it goes into deep sleep, it never wakes up.
I think it is because the nodeMCU draws so little power during sleep that the battery pack disables its output. If I press the power button on the pack the nodeMCU reboots and works.
Anyone have any experience with this or know a better and also cheap solution (no use having a 150$ power source for a 4$ chip). I would prefer it to be solar powered with battery backup so that I am pretty sure it will 'always' work. But I am open for just a battery powered solution. I would also prefer that it is usb, so that i can plug it straight into the dev board. I know that using the dev board makes it use more power, but I am not an electrical engineer, so i would prefer to keep it simple for now, I can always change it up later.

Thanks

- Wed Jan 13, 2016 12:17 am #38649 So here's the deal with most of those USB battery packs...
They suck.

You're exactly right in the assumption that the power draw is too low to keep it on, but honestly, the power draw is probably too low even when it's at full power, you just never reach the timeout period. We had this problem at work, and found that the only battery packs that DIDN'T have this timeout feature are the ones that have integrated flashlights. I can't say where we got them or what they were, but my guess is "from Amazon" and that's all I got.

I vote the battery pack off the island in favor of solar.

Behold the Microchip MCP73871
https://www.adafruit.com/datasheets/MCP73871.pdf

and as it turns out, Adafruit makes a nice breakout board to do exactly what you need.
https://www.adafruit.com/products/390

You'll save money if you just simply BUY the board, but if you're adventurous and need to learn, like me, then you'll roll your own.

BUT, I can vouch for Adafruit. They's good people. Buy the board and a LiPo, and be done with it. Also, the reason they're real adamant you use their LiPos and solar panels isn't so much that they want your money, but rather that charging Li batteries presents a bit of a liability (See Youtube for any number of Russian teenagers overcharging batteries by 500% and shooting them with BB guns)

Good luck with your project!

Andy

- Fri Jan 15, 2016 11:31 pm #38925

It works until it goes into deep sleep, it never wakes up.
I think it is because the nodeMCU draws so little power during sleep that the battery pack disables its output

Do you have XPD_DCDC connected to the RST pin?

- Sun Jan 31, 2016 4:29 pm #40109 This is a subject of great interest to me too! While I think everything Adafruit do is built of awesome, a $17 charge controller (plus whatever for panel and batteries) is not my ideal solution for a $4 chip, and I think OP would share the same view. In my use case, I need to make about 10 stand alone solar powered sensors. I don't have $170 to drop on the charge controller. My sensors read from the analogue pin, connect to wifi, POST the results to a server then deep sleep for an hour.

Right now I'm considering two options for the charger, and I'm looking for any advice about which one might be best to use.

For the battery, I will probably use a 18650 as they are easily available and cheap. I'll use a solar panel for power, but I'm not sure what specs, that kind of depends on the charger.

The two chargers that I've found that might be useful are:

http://www.aliexpress.com/item/Free-Shi ... 61008.html

or

http://www.aliexpress.com/item/Free-Shi ... 58256.html

The 18650 battery is 3.7v so I can either use a boost controller to lift it to 5v, then I could use it with a NODEmcu style board, or I could step the voltage down a bit to 3.3v and use a bare ESP8266

Paying no more than a couple of $ or £ (in my case) for the charger is what I'm thinking of. Can anyone see anything at this range that might work for Solar charging a battery, capable of powering an ESP8266 for about 20secs every hour?

I also need to find out more about MPPT and how important it is to all this!

Jim