AC50S Error E28

I received my AC50S from Bluetti in December of 2020 and am charging from my car’s 12V and running a small refrigerator on the AC50S DC cigarette lighter.

I am often finding the refrigerator is not running and the AC50S is reporting error E28.

The manual says “DC12V-1 input over current”

What does this mean and how do I fix it? DC12V-1 to my understanding is an output, why does the error refer to input? I sent an email to but haven’t received an response.

You turn on DC output when charging the unit, which will trigger the protection mechanism. Just unplug the adapter and reset the unit.

The AC50S Manual says in the FAQ “Can it charge and discharge simultaneously? Yes, but it is not recommended to charge and discharge at the same time in order to protect the battery life”

So are you saying that I cannot charge and discharge simultaneously otherwise I will get a E28 error?

I think your fridge is pulling too much current at times when starting and it is separate from charging with your car.

I’ve never had this error when using the AC50S and refrigerator except when charging. It has no problem running the fridge from 100% to 0%. Also the error for too much output current would be:
E27 “DC12V-1 output over current, Output current >11A or short-circuit”.

My error is:
E28 is “DC12V-1 input over current, Current >-1A”

Well, with your information and Bluetti’s reply above would make me now think that DC charging and discharging at the same time are not always compatible. Is this the first time you have tried that? If so, I would have to say it will not DC output significant amps while DC charging. If you have done this in the past several times without issue, that would seem more like a machine problem

It usually works and I’m charging and discharging right now and it’s fine. But it happens often enough that I’ve gone to my fridge and seen it sitting at 50 degree and E28 showing up that I want to know what’s going on. I wish Bluetti would respond what the error actually means, not just how to reset it. My guess would be the AC50S gets confused sometimes when discharging if you disconnect the DC charging input like when a car shuts off.

I wonder if it is as simple as the cig lighter plug or socket in the car is not making good contact and the combination of charging and discharging makes it more prone to a spike caused by a poor connection. The cig plug is notorious for poor connections. Just as an experiment, it may be interesting to try to improve the contact in the socket (clean with emory cloth on the end of a pencil eraser or try a little electrical tape wrapped around the cylinder part of the plug to tighten it. (make sure not to get tape on the metal side contact).

1 Like