I thought I’d share this positive experience, since usually people only bother to share when they’re frustrated. I bought an AC200MAX a couple of years ago, and I never used it with solar input until recently. When I did, I found that the State of Charge was fluctuating erratically and it had an extremely high power drain, so even on sunny days (with 400 watts of panels connected), it was losing charge most days (with negligible loads).
After trying the recalibration procedure and some other helpful suggestions by Bluetti customer service, I came to the conclusion that the BMS (Battery Management System) had some issues, being an older unit with older BMS version. I tried updating the BMS firmware to the latest, but it couldn’t get the newest (current) version, I believe due to the BMS hardware being an older iteration that could not work with the latest BMS firmware.
The only way to get the latest BMS version was to exchange the unit for a new one, and Bluetti customer service was very cordial and helpful by readily arranging the exchange, free of charge for me. I could see many companies not honoring such an exchange under the warranty, as the unit was still “working”, just not working as well as I would expect. Kudos to customer support for helping me with this without trouble, and being very friendly and helpful and patient throughout the process.
They did accidentally send me an incorrect replacement unit initially, but immediately apologized and replaced it again with a brand new unit. I ended up with what I was looking for, a new unit with an up-to-date BMS, at no additional cost to me. A big thanks to Bluetti customer service for handling this whole thing so well for me.