Building a solar cell 18650 battery charger + a voltage output circuit

Hello, I would like to use solar energy to use the voltage for some equipment I have. I want the final circuit to give me output 12 Volt, and I will use 18650 batteries, and I will need a battery charger for them. Can you tell me how should I start?

From a short search, I have found these:

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Hi,

The approach, afaik, is (...knowing what the batteries will be powering and checking they will be "large" enough and will last as long as needed...) to start at the end with the load, i.e. the batteries: voltage and current draw (presumably mA/h or A/h, peak and steady if so), from there perhaps it's advisable to put together a solar panel parallel or series string, unless one panel will suffice, to meet those requirements plus all housekeeping circuitry's (on the PCB) power needs, and from there select a suitable battery (solar) charger PCB as the bridge between both ends. Good luck. I'd avoid products with no datasheet or user manual.

Also, TI, STmicro, Analog Devices et al all have application notes or IC datasheets or even evaluation PCBs maybe that are very informative and help to understand these kind of circuits.

On Ebay always check the seller's feedback score. Is the price so low it's irresistible? Then be surprised if it gives high performance.

I want the final circuit to give me output 12 Volt

Click to expand...

One of your Ebay links is a charger that operates at a lower voltage. This won't help you achieve 12V. I think you want a unit that's ready-to-use. Naturally there's nothing wrong if you're eager to build electronics projects, such as a step-up converter.

You also need to explore the methods for charging batteries, whether one at a time, or in series.
What is your connector type for the batteries?
Enclosure?
Monitor?
Safeguards?
Do you intend for charger alone to be suitable power supply for equipment?
Etc.
These may influence your choice of solar panels, charger, etc.