I have a esp32 that is connected to around 5 to 6 sensors like ph, npk, dht , soil moisture sensor, soil temperature sensor and ldr module , so how to power it using a small solar panel of 6V (with 3500mah battery of 5 cells)and what components are needed to build the power supply system and i have to use wifi as well to connect it to laptop and is it possible to build the power system to power this project.
The first thing to do is establish an energy budget. Measure the average current required by your system.
Then, do the research to determine what capacity rechargeable battery is required to keep the system running for the longest foreseeable period without full sun, size the solar panel accordingly, and use a load-sharing charger like this one or this one.
Well, the very first thing to test with your project is to ensure the small solar panel can keep your battery charged 24 hours per day over several days. Estimate the current needed from your project and put a resistive load on the battery/charger to simulate the power draw.
thanks a lot for your valuable insight, and i am using basically to present it in the college
i am basically using it for demonstration purpose so i don't have long periods of operations and thanks a lot for providing me with valuable insights .
You mean some ready made device, battery panel combo?
If you mean the small panels, the size of a hand, you see on ali/eBay then forget about it.
You need a panel the size of a small fridge door to power an ESP32 24/7.
Leo..
I built my own solar system so I can tell you that the battery is the heart of the system. First figure out the energy budget. Since WiFi is involved it will use a lot of power. One thing many folks don't seem to know is that the sun does not shine every day. The ROT is to plan for 1 day of full sun (4 - 6 hrs) and 3 days NO sun. Sixe the battery bank for that.
Between the solar panel and the battery, you need a solar charge controller, either old-style PWM or modern MPPT. In your case, pick whichever is cheapest. Since the battery bank will likely not be the right voltage, the only other thing you need is a DC to DC converter. If all the electronics are 5V, then a single x to 5V, where x is the max voltage of the battery when in the absorption charge cycle. If mixed 5V and 3.3V, then add the required LDO or BUCK to get the 3.3V
Then why bother with the solar panel and charger?
My standard warning about solar power...
The solar panels specs represent the output at noon in an equatorial desert with cryogenic cooling. 
In real life the usable output is half to a third (depending on latitude and clouds) of the rated output.
Batteries are rated for a slow discharge to almost the point of failure. For normal loads divide the rating by 2 or 3 to get the usable range.
If you use WiFi determine when you will be connecting to the device and power down the WiFi the rest of the time. Don't run the WiFi at night.
If possible power down the sensors between readings. (We used isolated power to run the sensors to reduce noise. The isolation adapters used significant power - 500ma vs 20-40ma for just the sensors.)
I am writing this for the guys who used the search button, not for the OP.
I build FSBs - field sensor boxes - for sensors for a Large Property Perimeter Monitor system. these boxes contain sensors, a weather station that is distributed around the property, wireless IP cameras. many voltages are involved, so I use 12V lead acid batteries.. they are currently recharged by solar panels. I am transitioning to LiFePo batteries
solar power works like: Solar panel >> charge controller >> battery >> Load
you don't power from the solar panel. the panel provides charging voltage to the system. the charge controller regulates power to the battery. you get power from the battery.
Pardon Our Interruption... MPPT controller
Pardon Our Interruption... if you build battery packs
Pardon Our Interruption... straight replacement for lead acid.
Pardon Our Interruption... I use a larger version of this, which I have not found searching today
Pardon Our Interruption... and these, in various sizes, to distribute 12V, 5V and 3.3V throughout the FSBs
finally, these to bring solar power into the ammo box:
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