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FAQ: How to effectively combine multiple battery cabinets in a solar + storage system?

With advances in lithium-ion technology making batteries more affordable, reliable, and safer than ever before, energy storage has become more and more popular. Not only are more energy storage systems installed, but the size of the system often becomes larger. Many installers who are accustomed to installing smaller residential backup power systems need to complete completely off-grid and micro-grid island systems. This means installing more battery cabinets and more inverters at one site.
A common problem for energy storage installers is how to correctly combine multiple battery cabinets in a solar plus energy storage system.
Although smaller systems, that is, systems with one or two cabinets and an inverter, are fairly simple to install, larger solar plus energy storage systems are more complicated. Larger systems, especially those with more than four cabinets and more than three inverters, require a combiner box to connect all the equipment together.
Knowing when to use the combiner box is only the first step, because the combiner box itself has its own set of problems, specifically:
For many installers, the easiest option is to use a battery combiner box dedicated to the inverter. There are many options for the box, so it is important to choose the solution that best suits each project.
Companies such as Schneider and Outback provide system balancing equipment that matches their hardware, allowing installers to use their existing equipment. For example, Outback allows installers to combine up to nine FX inverters. With Schneider, installers can use up to three XW inverters in the switchboard. With Schneider and Outback, installers can use an integrated DC switchboard with an integrated disconnect to parallel multiple inverters, solar charge controllers and battery cabinets, if this is most convenient for the site.
In other cases, installers may wish to use separate DC distribution combiners for battery packs, solar charge controllers, and inverters (such as Midnite Solar’s MNBCB 1000). The ampere rating of the MNBCB 1000 is 1000 and it has a 250 ampere circuit breaker. The current of the four circuit breakers is 250 amperes, or 1000 amperes, which is a typical limit. The installer can then insert as many batteries as possible to actually install on the bus bar, usually 9 to 12.
On the other hand, products like Sol-Ark or SMA Sunny Island do not have hardware or existing enclosures, but rely on standard electrical industry combiner boxes. This helps to adapt to larger projects and various combiner box needs.
The second step is to adjust the size of the combiner box correctly. It is a common misunderstanding to determine the size of the combiner box based on the size of the battery; however, the inverter usually determines the maximum load for battery charging or battery discharge. Therefore, the installer should always determine the size of the conductor and the battery combiner box based on the inverter rating rather than the capacity that the battery may provide.


Post time: Sep-13-2021