Serial vs. Parallel Connections

Serial Connections• Serial connections are positive-to-negative

in a chain

Serial Connections – PV’s

• Voltages add– Higher voltage and lower current reduce

losses in wiring– Can exceed voltage capacity of charge

controller

• Reduces number of cables to combiner

• Current is the same through each device

Serial Connections – PV’s

48 volts

5 amps

An MPPT controller can take the 5 amps * 48 volts = 240 watts and charge a 24 volt battery with 10 amps (neglecting losses)

Parallel Connections• Parallel connections are

positive-to-positive and negative-to-negative

12 v

PV

5 A+ -

12 v

PV

5 A+ -

10 Abreaker

10 Abreaker

Parallel Connections – PV’s

• Voltage is the same across each panel

• Increases number of cables to combiner if multiple panel arrays are used

• An MPPT controller uses the actual array voltage

• A PWM controller sets PVs at battery voltage

• Current adds

Parallel Connections

12 v

PV

5 A+ -

12 v

PV

5 A+ -

10 Abreaker

10 Abreaker

12 volts

10 amps

Serial/Parallel Connections – Batteries

• Batteries must be identical

+ -12 v220 amp-hour

+ -12 v220 amp-hour

+ -12 v220 amp-hour

+ -12 v220 amp-hour

Serial orParallel ?

Serial orParallel ?

Volts?

Volts?

Amp-hours?

Amp-hours?

Serial/Parallel Connections – Batteries

• Batteries must be identical

+ -12 v220 amp-hour

+ -12 v220 amp-hour

+ -12 v220 amp-hour

+ -12 v220 amp-hour

Parallel

Serial

12 Volts

24 Volts

440 Amp-hours

220 Amp-hours

Serial Connections – Loads

• Current is the same through all loads– This is the current the source must provide

• Voltage drops between loads add• Voltage available for the next load in series is

reduced by the previous load• Failure of any load results in failure of all

Serial Connections – Loads

Current is the same through each load. If the total of all voltage requirements of all loads is greater than the voltage supplied some will have low voltage and may be damaged.

Parallel Connections – Loads

• Total current usage adds• Same voltage is available at each load• Failure of one load may not affect the others• Loads with mixed current requirements are not

affected (as long as the total current needed does not exceed system capacity).

Parallel Connections – Loads

•This configuration depicts multiple loads wired in parallel.•Each load is rated for the battery voltage. •The total current from the battery is the sum of the current through each load,

•even though each load pulls a different current

?’s