A second step seemed to do the trick for me, after cooling down the unit. Disconnect the incoming solar or wall charger power input cable. The code turned off immediately after I did that and powered off/on again. Unless the timing was coincidental to cooling down enough.
However, I also disconnected everything that was plugged into the EB (240 in my case.) – All AC and DC as well as from the rear outlet.
I also toggled the AC and DC power buttons back on.
And of course turned the main power off, cooling period, and back on, several times, without success.
My indoor/outdoor thermometer read 101/95 F today in my van. (I had survived 104/104 in the summer one day, but I remembered to turn off the EB 240 and unplug the solar input, without any problems. Then I read the manual and found out 104 is the allowed ceiling!)
Today I smelled electronics when I opened my van and saw the E021 error code. But so far the electronics seemed to have survived. I’m coming on 3 years full time van life w/ the EB240 and no issues. Very good quality control I would say.
If the temp gets hot (95+ in the van), I will shut the unit off plus disconnect the input cable from now on.
If it is true that there is a second step needed of disconnecting the input cable, that probably was overlooked during quality testing, which I am guessing is a simple software bug fix. Or by design to keep the unit from overheating again. Because the E021 code should trigger all electronic circuit breakers to trip off one would think. It’s possible they don’t. Unless it’s just a stuck error code that needs a software fix.
(The member who said above they don’t know why the code was not displaying in the morning – it’s probably because the sun doesn’t shine overnight.)
Footnote: 2 of my 4 panels are older, and have slightly different power specs. I have to disconnect then reconnect the solar input each morning once the panels are supplying power, or I only get power from 2 panels not all 4. Configured 2 Series 2 Parallel. That might be a factor in my E021 case, but probably not. (Bluetti support informed me that wouldn’t be an issue if all 4 of my panels were the same. 2S2P halves the voltage and doubles the amperage, but also results in something like 12% loss of power wattage. 4 Renogy 100s in series at max sunlight is too much voltage for the EB.)
Once again, these EBs were designed very well. And we should have the common sense to disconnect the input cable if the sun is shining and the unit is overheated. : )