As you might have noticed, different appliances have different ways of connecting batteries together. Some have batteries side-by-side, some have them one on top of the other. The reason for this is to provide the appliance with the correct amount of electrical power from a number of batteries. Here is a brief description why they are different and what each means.

Series Connection

When batteries are connected together in serial, the capacitance of the cells will stay the same (i.e. the Ampere-hour rating) as that of a single cell. The voltage in creases as a sum of the voltages of the batteries connected together. Here are a few equations you may find useful:

Total Resistance: R = R1 + R2 +...Rn

Current: I = I1 = I2 = ...In

Voltage: V = V1 + V2 +...Vn

Parallel Connection

When batteries are connected together in parallel, the capacitance of the cells increase with each battery added, however in this case, the voltage will stay the same:

Total Resistance: 1/R = 1/R1 + 1/R2 +...1/Rn

Voltage: V = V1 = V2 =...Vn

Current: I = I1 + I2 + ...In

(NOTE: batteries connected together should have the same voltage and ampere-hour ratings)

Other useful equations

Cell Capacity: C = IT

Cell Energy: Wh = PT = IVT

Power: P = IV = I2R

Resistance of a Conductor: R = V/I (0hms Law)

Key: I = Current expressed in amperes
V = Electromotive force (emf) expressed in volts
P = Power expressed in watts
R = Resistance expressed in ohms
Wh = Watt-hours
T = Time expressed in hours