BYD Battery LV Flex Lite and Sunsynk 5kw Inverter Combination Issue

Posted March 25, 20232 yr

Hi everyone

I've recently procured my first-ever hybrid energy backup solution. The stack consists of a BYD Battery LV Flex Lite (single unit), the BYD B-Box Premium LVS/LVL (BMU) and a Sunsynk 5kw inverter. Before diving into the somewhat detailed specifics of this post, to summarise, I cannot get this stack to shake hands and function as intended.

It's worth noting:

I am fairly new to the hybrid energy space with very little experience in electrical engineering
My expertise for the most part includes software development and programming
My knowledge of distributed computation with physical devices is limited to IoT with devices such as Raspberry Pis and sensors

With the housekeeping set aside, I've been trying to install the above-mentioned hybrid energy stack. So far it's been an unsuccessful endeavour even with technicians offering their advice. The first issue is that it does not seem like the battery and BMU are communicating at all. Attached is a screenshot (IMG1) of the end result after trying to commission the battery and BMU using the official BYD Be Connect 2.0 application - tested on 3 different mobile devices. Each test results in the same error "Internal Communication Failure 3" with no further description or cause based on the battery or BMU documentation. Also, the power button LED on the battery flashes blue once and white once. While the LED on the BMU flashes blue twice and white once - the documentation does not provide much description in this regard either.

Secondly, because the battery and BMU are not communicating correctly, there is no synchronisation with the Sunsynk inverter. What I find perplexing is that the inverter only ever detects two battery SOC% values, either 0% or 100% - there are no in-between values whatsoever, see screenshots as per the inverter display (IMG2, IMG3, IMG4 and IMG5 ). It seems that the inverter detects the battery but is unable to establish a proper connection given the failure in the handshake between the battery and BMU which is a requirement at the base layer for the inverter to operate and make use of the battery.

Has anyone else experienced a similar issue with the same stack? If so, were you able to remedy the issue? Any thoughts and recommendations would be highly appreciated.