Hi, I would like to ask you for advices in my project.
I am designing small "off grid" system for Arduino/ESP.
So let me give you some small introduction:
Arduino(s)/ESP(s) (multiple ESP, low consumption, most of the time deep sleep, aprox 7-15mAh per hour)
Battery: li-ion 18650, 2800mAh or moto battery (12v 10Ah)
Solar panel: 6/12V (10-30W)
I would like to have system which is offgrid,
which has enough energy on batteries during nights (winters) and during day will help to recharge the battery some small solar panel.
I don't wanna use some extreme PWM of solar panel which will have consumption half of the system.
Also it will be nice bonus if I can get information about battery into ESP(to know what is status of battery in cloud).
I expected to use just:
-> simple solar panel 12V 20W
-> stepdown/regulator from 10-24V to 5V
-> 4x
- TP4056 charging module
- 18650 Li-ion battery (2800mAh)
-> stepdown/regulator from 3-5V to 3.3V
But also think if I miss something what can improve it or something what I am doing wrong.
Thank you for any advices!
Just about everything is easier, cheaper and more reliable if you choose lead acid batteries for a small solar DIY installation. They take far more abuse than lithium based batteries, and if the setup will be outdoors, you don't have to worry about low temperatures.
If the system power consumption is low enough, you don't even need a charge controller, as trickle charging is fine. For example, there are 18V solar panels designed to keep car batteries "topped up" during long term storage, charging at around 100 mA.
For few Arduino/ESP8266 D1mini devices which will be "monitoring" few times per hour values on sensors and sent them by SIM800L as date to cloud.
I count that with deep sleep most of the time I can get (theoreticaly) to 15mAh consumption. So lets say that I didn't count it well so max 30mAh consumption. (720mAh / day)
So it must have battery which can support power in cloudy days at least for few days.
I'd recommend a low cost MPPT charge controller with USB ports and not try to switch or disable power sources. Go with the lowest cost LiFePO4 you can find that's 12v.
If the solar charge controller is going into a box to be shut away, do not get a solar charge controller with a display; the display is a waste of power.
Post#2 shows a diode off the solar panel. Solar panels will draw power at night and can be damaged. The diode prevents current from flowing from the battery to the solar panel. Use a Schottky diode.
