AC200Max Not reliable below 20% charge

I run my Keurig Supreme Plus Smart coffee maker (~1400watts for about 2 minutes) once or twice a week on my AC200Max and it drops about 2-3% each use which is fine. However, if the 200Max is at or around 20% charge it will sometimes drop to 0% without warning with an audible zap noise (from the inverter I’d imagine?). Today is the second time it did that. I generally try not to run it down past 20% for longevity sake but it’s concerning that it might just “decide” to not really be at 20% at all.

I didn’t really see anything else similar to this in the forums but has anyone else experienced this?


ARM: v4030.15
DSP: v4005.07
BMS: v1017.02


While the state of charge % is an estimation I’ve generally seen what you described with almost all power stations due to how the under-voltage protection for the battery functions. The higher the current load on the battery, the lower the operating voltage of the battery will be. As the battery gets closer to 0% the voltage will decrease and if you then put a large load then the voltage will drop too much and trigger the under-voltage protection causing the AC output will shut off to protect the battery. With the same 20% charge you will be able to use the station much closer to 0% with a smaller load (ex. 500W).

To illustrate this I made a quick and dirty diagram (this is purely to demonstrate the theory and is an approximation):


Thank you for the very informative post!
I appreciate the time you took to explain, in detail, what you believe it might be.
I did get the charge up to 6% before attempting to finish brewing my morning coffee and it worked just fine… I suppose I’ll just have to be more careful in the future not to try using very much of anything at or near 20% sadly.
Please correct me if I’m wrong but I thought Li-Ion and LiFePo4 batteries remain consistent voltage until drained?


You’re right, it’s true that Lithium Ion based batteries hold their voltages better than say lead-acid batteries:

That said, I’m sure there are other factors that I don’t know about that would contribute to power stations shutting down AC output below 20% SoC earlier than expected. Perhaps @BLUETTI can provide a more accurate explanation why this tends to happen.

@gglover Please provide your AC200MAX SN code (located on the bottom of the machine, consisting of 13 Arabic numbers) and I will have an engineer try to push a new BMS version to you.

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Can you please explain what this BMS version does to fix this issue? I’ve read others posts about the update and don’t want to update unless necessary.


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@gglover This BMS version is designed to optimize SOC accuracy.