I have a Sunsynk 5kw inverter with a Pylontech US2000C master battery with three Pylontech US2000B batteries. This December after the system had been running for two years the master US2000C failed (it was swollen on the structure) while the other three batteries remained in perfect condition. I am currently running on the remainder without any alarms or problems. I have sent the battery in for a technical report but I would like to know what could be the root cause of the problem.

On 2025/01/14 at 4:30 PM, PierreBenade said:

I have a Sunsynk 5kw inverter with a Pylontech US2000C master battery with three Pylontech US2000B batteries. This December after the system had been running for two years the master US2000C failed (it was swollen on the structure) while the other three batteries remained in perfect condition. I am currently running on the remainder without any alarms or problems. I have sent the battery in for a technical report but I would like to know what could be the root cause of the problem.

Impossible to say without more information.

Did you dowoad the logs before sending in the battery? If you did post them here and let's see if someone can assist.

The pouch cells used by Pylontech seems to be more sensitive to being charged at a to high voltage (when compared to a prismatic cells). This is just my personal opinion.