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?
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.
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.
Update: 11/24/23 - I’ve been using the AC200Max extensively after the BMS was updated, I find that it no longer cuts out past 20% and appears to be more accurate indeed. Thanks Bluetti support.
