When you’re building a solar battery bank, how you connect your batteries has a major impact on the battery bank’s performance. There are 2 primary types of configurations you can use: series and parallel. Knowing the differences between them, how to form these kinds of connections, and how they affect voltage, storage capacity, and your battery bank’s overall behavior are all important factors.
Series Connection
A series connection in a battery bank is made when you connect the positive terminal of one battery to the negative terminal of the next. The open positive and negative terminals at the ends of your bank would then connect to the inverter. A series setup increases the voltage of your battery bank, while the amp-hour (Ah) capacity stays the same. For example, two 12V, 100Ah batteries connected in a series become a 24V, 100Ah battery bank.
This type of connection creates a higher voltage, which also means a lower current. This can help reduce energy loss in the wiring of your battery bank and make it a more efficient connection for larger systems and longer cable runs. A series connection can also help your battery bank stay compatible with inverters that require a higher input voltage.
On the downside, when one battery in a series connection fails, it can affect the entire battery bank. This type of connection also requires careful balancing to prevent uneven charging, so it does increase the maintenance needs of your system somewhat. But perhaps the biggest drawback of a series connection is that it does not actually provide any increase in your battery bank’s total storage capacity, and typically, capacity is what solar users are looking for.
Parallel Connection
A parallel connection is formed when you connect the positive terminals of all your batteries to one another, and all the negative terminals to one another. The combined positive and negative leads are then connected to your inverter. In a parallel connection, the amp-hour capacity of your battery bank increases while the voltage stays the same. So, two 12V, 100Ah batteries in parallel create a 12V, 200Ah battery bank.
The increased total storage capacity is definitely the biggest benefit of this kind of connection, giving you the ability to run off battery power for much longer. The connections also create redundancy, so if one battery fails, others can still function.
In terms of drawbacks, it’s important to note that the higher current in a parallel connection can require thicker, more expensive cables, and you have a greater risk of uneven load sharing if not wired properly. Additionally, it’s a less efficient connection type for larger systems due to the increased current flow.
To confirm the best solar battery connection approach for your system, connect with a HomeGrid distributor for practical recommendations.