I purchased the Sonnen Eco Gen 2 16 kWh battery to integrate with my 8.6 kW SunPower PV array to provide most of our needs off grid and have a backup capability when the grid goes down. The system was installed in May 2018 and went operational in early June. As a retired engineer I was always intrigued by solar technology and based on the state of MA and Federal tax credits, maturation of the technology, opportunity to use reduce our carbon footprint, and provide backup power in outages decided to do some research and invest in a system. I chose the Sonnen Eco series based on the battery technology being the safest (as compared to Tesla Powerball 2 and LG Chem), reviews and opportunity to use the battery daily (versus a natural gas fired generator that is loud, high maintenance, etc.) and control it remotely as we travel frequently in the winter. Within a month of operation, we had a Cat 5 cable fail thus couldn't communicate with the built in inverter. Additionally, we had a HUB board failure that prevented the front panel from shutting the battery down that needed to be replaced. Additionally I learned that I needed to call Sonnen to change operational modes from Self Consumption to Backup which I'll explain next. In Self Consumption mode, the battery takes excess energy from the PV array not used by the home and recharges it so that in the evening, instead of using power from the grid, the home uses the battery. In backup mode the battery is essentially a "generator", staying fully charged until the grid goes down. Once everything was finally fixed and diagnosed in Sept. we discovered another issue which didn't arise during the summer as our larger appliances, e.g. electric oven wasn't used. Once we fired up our electric oven, and other units such that we instantaneously exceedes the 8kW rating of the Inverter, it tripped it's internal DC breaker and shuts down. While the grid is up, and in Self Consumption mode the battery, PV array and grid are wired to share the load. However, it appears that the Sonnen whole house monitoring system is sensing the peak usage for the entire house (as compared to just the battery output itself) as appliances come on and shutting the battery down rather than self limiting itself. The Sonnen Tech and training instructor who visited us to fix the Hub board said he has always thought and taught that the Self Consumption mode should not shut down this way. So we're still waiting for Sonnen's response and operating backup mode as this limits the battery to be only used should the grid go down and will only power essential loads. Hopefully they'll figure it out and make the needed changes. What I thought would be the "Ferrari" (high end and most expensive) of solar batteries hasn't lived up to expectations.
