Having made a couple of home-made batteries which only produced about 1 volts each, I realised that it would be useful to be able to increase this voltage to power a LED light. You may be thinking 'connect 2 in series' but there are disadvantages with this.

This voltage booster increases the voltage. It has leads with alligator clips, so it can be used on different projects.

It is simple and cheap to make.

Step 1: Dismantle a Solar Garden Light

Dismantle a cheap solar garden light. The one used cost $2 and was dismantled by unscrewing a couple of screws. Just the circuitry is required so you will also have a battery holder, small solar panel, rechargeable battery which can be used in future projects. Not bad for $2.

Step 2: Attach Hookup Leads

Take 2 crocodile clip leads. Cut each lead in half. Soldier 2 of the halfs to where the battery was connected to the circuit board. (Input) and the other two to where the LED light was (output).
A housing made from some rolled up beer can was placed around the circuit board and the black insulation tape wrapped around.

Step 3: Test Voltage

Voltage across the LED was tested with out the voltage booster and it read 1.38 v, as expected this was not enough to light it.
The booster was added and the LED lite up BUT when the Voltage was measured it was only 1.36 v, it was expected it would be more.
A capacitor was then added to the circuit and the the voltage reading was - 5.30 v. I don't know why this would be. If you have any suggestions please leave them in the comments.

Step 4: Using the Voltage Booster

The voltage booster is usefull to light a LED with just one battery and for testing out home made batteries such as this one : https://www.instructables.com/Recharable-Tin-Can-Battery/