Adding a battery to an existing battery pack

When incorporating an additional battery into a system, it is crucial to ensure that the battery voltage and State of Charge (SOC) percentage are closely matched. The SOC reflects the available capacity of the battery relative to its full capacity. Maintaining similarity within these parameters is essential for achieving balanced performance.

If the added battery deviates significantly from the existing battery in terms of voltage or SOC, issues related to unbalanced batteries may arise. Unbalanced batteries imply that they are not synchronized in terms of their energy levels. This imbalance poses a risk where one battery could potentially discharge to a very low level while the other remains at a higher SOC, such as 50%.

To avoid such imbalances, it is recommended that the additional battery's specifications closely match those of the existing battery, with a permissible deviation of no more than 5% on either side of the specified values. This ensures harmonized operation, preventing scenarios where one battery undergoes excessive discharge while the other retains a substantial charge. A well-balanced battery system contributes to optimal performance and longevity of the overall energy storage system.

In addition, we also strongly recommend that when adding one or more new Batteries to an existing Plant that the new Battery (or Batteries) become the new Master Battery with any additional new Batteries as Slave1 etc and the original Batteries becoming the last Slave / Slaves of the Battery Bank. This is particular to older SunBatt Batteries where the BMS software of the newer Battery may be higher revision than the BMS software of the originals. New software will always recognise older revisions.

Please Note that the above statement is not the case for L5.1, L5.3, G-Series and new W-series Batteries as Sunsynk Support are able to update the software of these newer models of Batteries remotely (providing the Plant is online)

After the additional battery has been connected into the system it is essential that all batteries charge up to 100% in order to calibrate before being used in normal operation.