Determining requirements (solar cell, battery, LiPower device)

Calculations:

We wanted to give a 5V device 1550mAh

We looked for a battery that would give us at least that amount of power. So our battery is 7.4Wh. Watts, or power, is equal to voltage times current (amperage). Or battery is 3.7V*2Ah = 7.4Wh...

P=IV, Power = Current*Voltage

But we're also adding a variable to time to it in Wh. The equation therefore becomes Pt=ItV.

So, we knew which battery to get because 5V*1.5Ah=7.5Wh, which is close to the battery we got. We can swap out our battery for a larger one later if it all works well. This is all for a prototype.

Now we have the battery.

The other calculation we did was for the size of the solar panel. We knew that we wanted to charge this battery to full in a reasonable amount of time, so we looked for a panel that was not too large but could collect a decent amount of energy. The panel we chose is 5.2W. To charge a 7.4Wh battery, it would take 1.42 hours to charge the battery fully (7.4Wh/5.2W).

There is only one kind of Sunny Buddy that is easy to work with, so there are no calculations needed.

Because the battery only puts out 3.7V, we needed a device that would step that up to 5V. That is what the LiPower does.