Module extension / 30% SOC rule

Modified on Mon, 31 Oct, 2022 at 12:23 PM

For module expansion, please follow the 30%SOC rule. Details see below:

Note:It is important that all modules of a storage tower have a similar state of charge (tolerance 5%). New modules have approx. 30%. Therefore please add the new module to the existing storage only when the storage is charged between 25% and 35% (see instructions, downloadable at www.eft-systems.de). Do not forget to adjust the number of modules in the configuration if necessary.

Note: when modules of different state of charge are combined, there are sometimes significant capacity losses and SOC anomalies at system level due to series connection within the tower. The 30% rule is therefore referred to in both the instructions and the service checklist:

- Instructions (see page 65): https://docs.eft-systems.de/download/0c99b803c0&_lang=en

- Service checklist: https://docs.eft-systems.de/download/DOC-00044&_lang=en

The easiest / most pragmatic way is to involve the plant operator. The existing storage tower is already in operation anyway. The system operator can track the state of charge of the storage most easily. If the storage is at about 30%, the operator can easily switch off the storage by pressing a button on the BCU for 5 seconds. If the battery is then switched off it holds the last SOC for weeks. You then have the possibility to plan the use for expansion and then find the battery at 30%, so you can easily integrate the expansion module.