Arduino Pro Mini 3.3v - solar power - How?

Projects General Guidance
1

Hello to all!

I would like to create a meteo-station self-powered via solar panel. It would use the libraries developed on mysensors.org, which are using nrf24l01+ network radios. I've create the whole structure (GW, controller, nodes) and all works well. Now I would like to create an outside station, self powered.
I've read a lot of artcles about how to recharge a Lipo Battery and power up an Arduino Pro Mini 3.3v but I'm really confused now...
So, could someone give me some hints? I know there are boards they do a lot of the charging stuff, but I would like to spend less as possible and try to create something by myself :wink:
AFAI've understood, let me explain what I should need:

1 solar panel. Which one shuld be the best? If I use a solar panel over 6V output, should I use a DC-DC converter like this?
http://www.aliexpress.com/item/Free-shipping-LM2596-Power-Module-DC-DC-Buck-Converter-Step-Down-Module-LM2596-High-Quality-Wholesale/32363769998.html
Also better higher voltage and a Step down converter or a 6V solar panel without Step down converter?

1 battery charging module. Which is better?
BOARD1
http://www.aliexpress.com/item/5PCS-Micro-USB-5V-1A-18650-Lithium-Battery-Charger-Board-With-Protection-Module/32216806621.html
OR BOARD2
http://www.aliexpress.com/item/5pcs-lot-TP40561A-Lithium-Battery-Charging-Board-Battery-Charger-Charging-Module-Free-Shipping-Dropshipping/1084643386.html
I've only seen the first has a battery charging protector and it has another two pins: OUT+ and OUT-. Which should I choose and why?

1 Lipo battery
Should I take a little 1000mA Lipo battery like this:
http://www.aliexpress.com/item/Syma-X5SW-X5SC-Spare-Part-3-7V-1000Mah-25C-Va32-Upgraded-Lipo-Battery/32442170507.html
OR is better a 18650 battery, i.e. 3000mA like this?
http://www.aliexpress.com/item/18650-battery-Ultrafire-bateria-3-7V-3000mAh-Li-ion-Rechargeable-Battery-Flashlight-batteries/32276505592.html

Then, If I use a 1000mA Lipo and the BOARD2 I should need change the resistance from default to 3K to give an output of 400mA to avoid damages to the 1000mA battery. Is it the same on the BOARD1? Have not find the resistence.

And, where to connect then the Arduino Pro Mini? On the BOARD1 there are the OUT pins. What about BOARD2?

And, again, if I use a Pro Mini 3.3V, could I attach it directly to the VIN power? Seems yes, the ATMEGA works from 1.8V up to 5, but to be sure.

So, I've a lot of confusion, please, help :slight_smile:

Thanks a lot!!!

Simon

2

See this great project description of a solar powered Arduino + NRF24L01. You could use a much smaller solar cell.

3

Hello!
Thanks for the answer. The project you mentioned is really interesting, but seems very complicated for my knowledges :slight_smile: This is the reason why I would like to use some boards, and btw, I still remain with all my doubts :frowning:

Simon

4

I know there are boards they do a lot of the charging stuff, but I would like to spend less as possible and try to create something by myself :wink:

Very bad idea.
LiPo is a potentially explosive/firehazzard technology. Charging boards are (supposed) to bebuilt with safeguards. Boards are designed or jumpered for specific battery technology. IMO anyone asking how to do this is in no position to design-build a charger. Leave thedesign to knowledgable professional and just buy whatyou require... Solar charged LiPo is not a technology to self-learn. Adafruit

Ray

5

mrburnette:
Very bad idea.
LiPo is a potentially explosive/firehazzard technology. Charging boards are (supposed) to bebuilt with safeguards. Boards are designed or jumpered for specific battery technology. IMO anyone asking how to do this is in no position to design-build a charger. Leave thedesign to knowledgable professional and just buy whatyou require... Solar charged LiPo is not a technology to self-learn. Adafruit

Ray

I totally agree, but, isn't this already the charging module?
Charger-Board-With-Protection-Module

So I need only the other parts to acomplish the final result.
Sorry, but really I'm really noob but would like to setup something by myself :wink:

Thanks,

Simon

6

You are starting at the wrong end of the project. You need to build the circuit and analyze the current consumption while it is working as expected.

Then you need to plan for the amount of sunlight in your area during the entire operational season and choose a solar panel accordingly.

Battery capacity is chosen to supply power for the number of days the system must run during bad weather.

7

So I need only the other parts to acomplish the final result.
Sorry, but really I'm really noob but would like to setup something by myself :wink:

Thanks,

Simon

Simon,
The unit you are pointing to is "pre-adjusted" for a charging-current. This value may need to be adjusted for the specific LiPo cell based upon cell "capacity" and not cell physical size. You need to size the battery capacity to your worst-case needs, identify the battery (pack) and then select the proper charger voltage/current. "18650" cells vary much.

Ray