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.
