I figured I would create a fresh topic for this failure with my AC2A and my Resmed mini CPAP running on AC connected to the Bluetti. This seems like a software bug with the BMW controller or unit.
When searching for this error I found a post on here from about 6 months ago for an AC180. The OG post seems to indicate it may have been a heat related issue.
In my case, i was in cold weather but no where near the published limits of the unit.
Whats interesting to me is that in my case I had my AC2 connected to another brand (and ‘dumber’) unit effectively putting the unit in grid or passthru mode.
Hoping there is a software patch to help sort this as ive seen on other threads. Any help resolving this would be appreciated. Essentially, this unit has plent of power for my resmed mini (which only pulls 20w) but with this weird and repccuring failure its unuseable and unreliable.
Here’s my original reply to the older post:
So, I have an AC2A and last night while I was using my mini CPAP I noticed that it was shutting down power flow to the AC side causing my CPAP to fail. Once the error cleared it would begin functioning again. This happened a dozen times before i finally switched over to the other brand generator I also have.
When I looked up the error, it showed the E074 code and while researching I found this thread.
Here’s my configuration:
AC2A connected to the AC port of a different brand but higher capacity solar generator. Effiectively putting it in “Grid Mode”.
Firmware and software all up to date as of today’s date according to the app.
Temprature inside the Jeep that i was sleeping in was 40F-46F. These temps weren’t even that extreme.
One thing I do notice is that while in pass through mode there is 000w showing on input and output of my unit. (Is the AC2A incapable of measuring flow through it while in “grid” mode?)
I have 3 x AC180s and an AC70. I recently set 2 of the 180s and the 70 up in UPS mode at home for my wife, as I was away. This was in the event of a grid fail for back up power, as my wife is not able to connect everything.
All 3 units showed the output load of what was connected, here were the observations I made.
AC180-1 connected to house fridge. When cycling draw was approx 150W.
AC180-2 con. to large TV and desk for laptop, LED light and mobile phone charge, approx 100W
AC-70 con to home WiFi router and fibre optic input, load was a constant 25W.
The other noted obs. was that as all 3 units were at 100% charge the input load showed the same as the output load. Occasionally the fan would start and I noted the input still showed the same as the output Watts i.e. on the AC70 = 25W in, 25W out. I believe this is because the “smarts” of the power station, interrogate the battery BMS to check it is full with a brief charge (tickle), then stops the charger. I am on 240VAC in my country.
One thing I have noted, if I plug in a low W device such as an electric toothbrush charger only, the W display shows zero as the load is below the threshold of being measured. Wether it charges I am not sure. I use a small 150W inverter in my RV for this item as it is powered during the day when on solar from the RV house batteries. All of the above is at a temp of 25C (77F) and in the optimal range.
Forgot another point. I don’t know actual voltages if you are in the U.S. at 120V, but the same scenario may occur as does here.
Our grid voltage is 240VAC, I’ve measured it with a power meter under low load and up to 10A (2,400W) and it is consistently 240-241VAC.
However, the AC180 (the unit tested) hovers around 230VAC under low load and can drop to nearer 220VAC under a higher load i.e. my RV microwave draws 1,250-1,300W and I see the voltage go to 223V approx. These voltages were taken with a power meter as the Bluetti only shows Watts. I just checked one of my 180s, its no load voltage was 232V (no grid connect, fully charged). Is your CPAP machine voltage sensitive? in that a lower voltage may affect its operation.
As an aside, I have a 540lt home fridge freezer and a small 90lt bar fridge (a cheapie). The home fridge is an inverter compressor, draws around 150W and behaves perfectly from the AC180.
I plugged in the 90lt, which draws 90W and it did not like running from the 180. It would appear that it does not like the lower voltage. As it is only a drinks fridge, I don’t really care if it’s off in a grid outage as I can put a few cans into the big fridge anyway.
My point being, it’s not the Bluetti in this instance it’s the device and the only one I have that has an issue.
Hi @dmulk, I appreciate your interest in Bluetti.
E074 indicates a BMS system fault, but it’s not specific enough.
Please log into the Bluetti app, click the SOC icon in the center to enter Battery Information, then click on the Pack1 icon to find the specific Alarm and Error codes (starting with the letter P).
Ok, I will attempt to repro this during my next cold weather outing…but it might be a while.
In the mean time, is there any data on my unit that I could provide you to see if there is a newer firmware that might help with what appears to be a cold weather BMS issue (In moderately cold weather temps) interrupting the AC inverter putput path?
Thankfully i had a different brand unit i could switch over to but this makes the bluetti all but unusable (and arguably dangerous) for a CPAP.
Hi @dmulk, Thank you for getting back to us so quickly.
Yes, it is, please tell us the AC2A’s SN number and current firmware version, we would like to check if there is a new firmware for you.
