Here's the Thundersky logo on the internal cells. Everything inside the battery & BMS was actually pretty robust and even the copper busbars were tin plated. This is excellent. Unfortunately the torque on each busbar was really far too loose, and the battery case Mastervolt used during this vintage, did not allow for an individual to easily check the terminals for proper torque.


When I conversed with Mastervolt about their self discharge claims, which coincidentally were identical to the Thundersky documentation for bare cells, they admitted they had no idea what the quiescent draw (phantom load) of the massive BMS on this battery actually was? On this vintage battery there was no possible way to shut down the BMS or isolate it from the cells, so the 3% self discharge claim per month was, in essence, grossly inaccurate because it was based only on bare cells and not inclusive of the BMS's quiescent load.


How on Earth can you sell a $10,000 battery, and make a self discharge claim (based on bare cells) without knowing the actual parasitic draw of your own permanently mounted BMS? Seems odd but things can tend to get looked over.


WARNING:


DO NOT open a Mastevolt LFP battery of this vintage and remove the BMS from the cells. Mastervolt claims they programmed in a self destruct mode into this BMS. This process is kept so super secret that they won't even disclose how to disconnect the BMS safely.


The Debacle:


All I wanted was to order new cells for the battery and get this back up and running. Mastervolt did not even offer replacement cells nor would they sell them to us. We could easily have purchased them elsewhere, but chose not to because the basic design was so fraught with issues, I decided it was simply throwing good money at bad to invest in new cells.


Mastervolt also refused to warranty any part of this battery for the customer, which BTW was installed with a COMPLETE Mastervolt system, though I do recognize it was beyond warranty. However, as the customer stated, Mastervolt made pretty bold claims about cycle life which failed to come anywhere close to a reality due to the inherent design and voltage guidance. Frustrating to say the least.


Still, with an out of warranty battery, they could have at least explained how to disconnect the BMS so it would not "self destruct". In the end I decided it was not worth throwing money at this design so the battery was simply scrapped.