What it means

EcoFlow E04 means the battery voltage fell below the safe minimum and the unit shut down to stop the cells being over-discharged.
Sometimes the pack simply ran flat under load.
Sometimes it's a unit that's sat unused for months and self-discharged deeper than usual.
Occasionally it's a charging cable or input that wasn't actually charging when you thought it was.

Affected Models

EcoFlow DELTA / DELTA 2 / DELTA Max / DELTA Pro
EcoFlow DELTA 2 Max / DELTA 3
EcoFlow RIVER 2 / RIVER 2 Max / RIVER 2 Pro
Older units stored flat for months are the most prone to this

Common Causes

Battery genuinely discharged to empty under load
Unit left unused for months and self-discharged below the normal floor
Charged from an input that wasn't really delivering power — faulty cable, dead car socket, weak solar
A high startup surge briefly dragged the voltage under the threshold
Ageing pack that sags hard under load
Cell imbalance pulling one cell low before the rest

How to Fix It

Put it on AC charge for a couple of hours.

A deeply drained EcoFlow can show E04 (or a near-zero charge) for a while before it wakes up properly.
Use the wall charger for the recovery charge — not solar or the car socket — and give it time.
Check the charger is actually working.

Within a minute of plugging in you should see the input wattage and the charge level climbing on the screen.
If nothing happens, swap the cable and try a different outlet.
A tired cable, or a car socket that's only live with the ignition on, is a common false alarm.
Power-cycle once it has some charge.

Hold the main power button to shut down, wait 30 seconds, and restart.
E04 should clear once the pack is back above the safe threshold.
Don't let it sit empty.

Lithium packs left flat for months drift down and can be hard to recover.
Store an EcoFlow at around 30-60% charge and top it up every few months — that prevents most E04 surprises.
If it drops to E04 again under load, the pack is worn.

A unit that charges fine but trips E04 almost immediately when you put a load on has a worn pack or a failed cell.
Contact EcoFlow support — under warranty that's a repair or replacement.