USB Type-C Dead Battery

USB Type-C (usually referred to as USB-C) chargers support a fairly sophisticated protocol for selecting charging voltage and current. What is important, when nothing is connected to a USB-C port, no power is provided. The device that wants to be charged must tell the charger what it wants. Otherwise no charging takes place. This is designed so for may reasons, but the simplest explanation is: a connected device may not want to be charged at all: imagine using a USB-C cable to connect one charger to another charger. If there was any voltage present by default, the result could be catastrophic.

The simplest way to tell the charger to offer the default 5V (as in USB-A legacy chargers) is to use the so-called Dead Battery mode. This is described in Section 4.8.5 of the Type-C specification. The device that wants to be charged (known as the Sink) must apply 5.1kΩ resistors to both CC1 and CC2 lines (pins).

The term Dead Battery (from the Type-C specification perspective) describes a device that is unable to conduct proper USB Power Delivery negotiation which requires active protocol implementation (usually a microcontroller) on the device. Or - the device has a microcontroller, but has no power to run it, hence falling back to this resistor-based passive indication that enables 5V on the VBUS line from the charger.

The Type-C specification was released 12 years ago. USB-C ports are now standard on almost all chargers and all USB-powered devices. Yet still there are many (and I do mean many) devices that do not have the 5.1kΩ resistors on the CC lines.

The result? Such devices will not charge from a USB-C charger.

They typically ship with a USB-A (the legacy "old" USB plug) to USB-C charging cables. And they require USB-A chargers.

The omission of the "dead battery" 5.1kΩ resistors is not only a functional issue. A device that does not support charging from a USB Type-C port (e.g, because it lacks the 5.1kΩ resistors) is illegal in Europe. The EU Directive 2022/2380 (often called the "Common Charger Directive") mandates the entire USB Type-C specification is supported - which includes those resistors as a core requirement for a device to function.

So 12 years since the standard went public, 4 years since it became legally mandatory, are product companies still trying to shave $0.001 (one-tenth of a cent) from the bill of materials (BOM)? Or is this just a pure ignorance?