Introduction: Big Phone Battery

About: Married to Domestic_Engineer (but I call her Meghan).

Run a smart phone directly from a car battery and/or solar panel. Useful if the USB charging port is broken. Or you need a huge cellphone batty.

For 6 bucks you can get an old smartphone online using Ting --

Step 1: 12volt to 3.7volt DC-to-DC Converter

The cell phone battery gives 3.7volts. So you need a 12volt to 3.7volt DC-to-DC converter.

Step 2: 'trick' the Phone Into Thinking It Has a Battery

Cell phone batteries are fancy. They usually have a built in thermistor. You can replicate this using some resistors. You can figure this out by measuring the resistance between each terminal of a cell phone battery.

Step 3: Video

Here is a little video. For proof.

Step 4: All Wired Up

The wiring goes like this:

Solar panel (~16Volts) -> solar charger controller (goes from ~16 volts to 12 volts)

->car battery (12volts) -> DC/DC converter (12V to 3.7V) -> phone battery terminals.

Step 5: 3.7 Volts

A regular cell phone battery will range from around 3.4V to 4.2V.

3.7 is towards the middle, so you won't get a full battery symbol.