How to connect your batteries to make up a 24V or 48V system
For larger systems with more than a couple of panels there are some advantages in running at a higher voltage:
- DC cable losses are reduced
- At higher voltage many charge controllers can run more panels
Most batteries are rated at 2V, 6V or 12V so you will need to connect them in series in order to reach the voltage you require.
Connecting batteries in series means connecting the (+) terminal of the first battery to the (-) terminal of the next battery. Each battery you connect in series increases the voltage of the battery bank.
Here are a few examples:
Two 12V batteries connected in series, the total voltage is 24V
Four 12V batteries connected in series, the total voltage is 48V
Four 6V batteries connected in series, the total voltage is 24V
What voltage should I run my system?
The voltage of your panel must be higher than the voltage of your battery bank. This is because most charge controllers are only able to step down the voltage from the panels to match the battery, and they can’t step it up.
- Small panels (100W, 150W) are usually rated at 12V or 18V so in this case you would require a 12V battery bank.
- Larger panels are often rated 24V or 30V (such as the 250W ) and in this case you will do better with a 24V battery bank.
- If you are installing several panels you can connect them in a string in order to achieve a higher voltage. Larger systems are best designed to run at 24V or 48V.
Advanced setup: connecting batteries in series and parallel
Suppose you have four 12V batteries but you want to put together a 24V battery bank. You could connect a pair of batteries in series, and then another pair of batteries in parallel.