Balcony-battery manufacturer says cells were not responsible for German fire

Battery manufacturer Zendure has investigated the cause of a fire in one of its battery energy storage systems (BESS) and told pv magazine neither BESS nor its cells were responsible.

In late March, a 2.4 kWh lithium iron phosphate (LFP) balcony BESS caught fire in Neuenhaus, in the German state of Lower Saxony.

Zendure ruled out the battery cells as the cause of the fire after observing no deformation or expansion in the product’s AIO2400 battery packs.

The manufacturer, which investigated the scene of the fire, said it observed a contact problem within a maximum power point tracking (MPPT) connection which led to elevated temperature. System logs from the BESS internal monitoring system also revealed the error, according to Zendure, which said there was also a problem with the network connection.

The manufacturer said the microinverter repeatedly attempted to connect to the internet for approximately 10 hours without success. During that time, the system operated with “impaired system stability,” according to Zendure, with voltage fluctuation increasing the microinverter’s operating temperature. A short circuit at the MPPT connection was detected and led to the device’s shutdown.

In addition, Zendure said, the operator failed to recognize and resolve the error message in a timely manner. That led to an increased fire risk, according to the US company. The plant operator noted, in a conversation with pv magazine, he had not received an error message in the system, a development likely related to the faulty network connection. An error message would not have contained any specific instructions for action to effectively avert the damage.

Zendure summarized the reasons for the fire as follows:

1. The microinverter’s unstable grid connection affected system stability.
2. A possible contact failure at the 400 W MPPT connection led to a local temperature increase and accelerated the fault development.
3. The system malfunction persisted for an extended period of time without prompt intervention.
4. The interaction of several technical and external influences ultimately led to the incident.

Zendure said it is using the incident as an opportunity to develop additional safety systems. The company said the user interface of its app will be improved so that error messages are more visible in future and an enhanced emergency shutdown function will be added. In the event of what Zendure termed “high-risk errors,” its systems will enter shutdown mode to prevent damage.

In addition to existing notifications in the app, Zendure said it also plans to inform users about system malfunctions via email or other channels, if necessary, so future error messages will no longer go unnoticed.

Zendure also aims to improve its system’s user guidance, for example through video tutorials.

From pv magazine Deutschland.