Wiring your batteries in PARALLEL vs. SERIES

Parallel vs. Series is an extremely broad subject.  This discussion is only regarding wind turbine and solar PV systems.

PARALLEL:

Wiring your batteries in parallel will not change the voltage.  However, it will increase your run time, or Amp hours (Ah) of your battery bank.  For example, two 12V 100Ah batteries wired in parallel will result in a 12V battery bank with a max capacity of 200Ah (100 x 2).

Advantages:

• Wiring in parallel is a great way to boost your run time (capacity).
• If one battery dies, you can still continue operating with the other one since the system voltage won’t change.
• Lower voltages are generally safer, however, anything under around 60VDC has about the same amount of safety.
• Wiring in series can allow you to add batteries later on, months or years after your project has been in operation.

Disadvantages:

• Voltage drop can be an issue, especially when working with high currents. Wire sizes need to be increased and care must be taken to avoid overheating wires and components.  Luckily for you though, Cutting Edge Power has that covered!
• Wire sizes can get very large when running big battery banks with large inverters.
• Long wire runs can be challenging because wire sizes are so large.

SERIES:

Wiring your batteries in series will increase the voltage.  It’s a simple calculation of just adding the voltage of each battery.  For example, two 12V 100Ah batteries wired in series will have a voltage of 24V (12 + 12 = 24).  The amount of run time, or Amp hours (Ah) will not change by wiring in series.

Advantages:

• Higher voltages allow you to use smaller wire. This is very helpful for long wire runs because smaller wire is generally less expensive.
• If you have two 6V batteries, this is a perfectly acceptable way to obtain a “12V battery”.
• Voltage drop is a common calculation for low voltage systems. The math is a little complicated but voltage drop is generally less of a concern for higher voltage.  Voltage drop can trip circuit breakers, overheat wire, cause alarm conditions with inverters – not good.  You shouldn’t have voltage drop problems with Cutting Edge Power products, but if you’re designing your own projects it is something you must always consider.
• Since components rated for 24V DC don’t require as much current, they can typically be smaller and more lightweight, which means they could be less expensive.

Disadvantages:

• Some devices are difficult to find in 24V. For example, DC to AC inverters are typically much more expensive in the 24V version compared to the 12V version.
• Most DC components are rated for 12/24V, meaning they can be used with either. HOWEVER, not all components are, for example: A cigarette socket wired for 24V will probably fry any device plugged into it.
• Having an issue with one of your batteries that’s wired in series could take down your whole battery bank. When wiring in series, you are limited by your “weakest link”.