The solar cells will recharge a battery during the day and a Light Emitting Diode (LED) will provide a bright source of light during the night. It can be used as a nightlight or a flashlight during an emergency situation.
Purchase a solar powered lawn ornament or patio light. You'll want one that can output about 5 V with as much current as possible. The more power it produces the longer the light will last in the dark. To keep things simple, find a unit with at least 4 LED lights. It will have sufficient power for this application.
Look for a low-voltage unit that includes rechargeable batteries. This way the battery holster and solar cell will already all be integrated.
Purchase a penlight flashlight with a bright LED. This will be the new light bulb for the portable solar light as the ones on the patio ornaments usually do not provide as much light.
On your solar garden light, open the housing containing the solar cell and disconnect the wires to the string of lights. You may need to de-solder the leads of the wires or carefully clip them with cutting pliers. Ensure not to short the two leads together as this may damage the battery.
Dismantle the flashlight and remove the high-power LED and connecting wires. Note which wire comes from the positive (+) lead.
Connect the + wire of the LED to the + terminal of the solar power and battery array. Connect the other lead to the - side. If the battery is charged, the LED should turn on.
The solar cell from the lawn ornament will usually have a day/night switch that will automatically turn on the light when the sun sets. If you want manual control, an on/off switch can be added between the + lead of the LED and the solar-cell & battery. Ensure the connection is solid to make the entire unit robust.
This is a brief introduction on how to build a portable solar light. Lights may vary, so modifications may be needed.