!!
critical Noco
Error Code Error LED: Solid Red
Reverse polarity detected.
? What Causes This
Incorrect connection of the battery cables.
✓ How to Fix It
Disconnect and reconnect the battery clamps with correct polarity (ensure red cable connects to positive terminal, black cable to negative terminal or vehicle chassis).
Source: page 7 of the official manual
From the manual
This error code appears in:
Noco Gb40 Boost Jumper Lithium Jump Starter