1, used for lighting. Online shopping 12V - 80VLED wide power lamp, connected to the positive and negative terminals, and equipped with a switch, you can easily use as a bedside lamp. It can be read in bed, and it is convenient to switch on and off the lamps when going to sleep and getting up at night. It can also be used as backup lighting in case of power failure.
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2, power the router at home, so that the phone can be connected to the Internet in case of power failure.
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3. Build a 12V to 5V circuit with LM317 and weld a USB socket at the 5V port. It can be used as a power bank at home. The same circuit can also be used to make 4, 2V or 3, 65V output voltage circuit, in the maintenance of electric bicycle ternary lithium\/lithium iron phosphate battery pack as a balanced charging power supply.
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4. Buy or find one or several solar panels with output voltage above 14V and maximum current above 2A in parallel and installed on the roof. Provide energy support for car batteries. The rich power can be used to charge the electric bicycle at home after the inverter is boosted.
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The above is my personal use of the car to replace the starter battery. After a few years of use, the capacity drops too much, and you can't charge much electricity, and don't throw it away. Take it to the junk yard -- the going rate is $4 a catty. A 12V60AH car battery can sell for over a hundred.