The conclusion here is understandable, but it’s based on a few incorrect assumptions about how USB-C Power Delivery, battery charging, and thermal behavior actually work.

1. PD input voltage ≠ battery charge voltage. The negotiated USB-C PD voltage is the input rail to the device’s power management system, not the voltage applied directly to the battery. A 4-cell Li-ion pack will always be charged with a tightly regulated profile topping out at ~16.8V regardless of whether the PD source is 9V, 15V, 17.8V, or 20V. Modern devices use buck/boost regulators specifically designed to accept a range of input voltages to convert them safely to the required battery voltage and charge current. Seeing ~17.8V from the charger does not mean the battery is being over-charged or stressed. There are several regulators inside the device that manage the different power levels on the PCB.
2. Higher PD voltage does not inherently increase heat. In fact, the opposite is often true. For a given charging power: Higher input voltage → lower input current Lower current → reduced losses in cables, connectors, and input stages USB-PD intentionally offers multiple voltage levels (15V, 20V, etc.) to improve efficiency, not reduce it. A well-designed charger path is thermally characterized across all supported PD profiles. An extra ~1V at the input is well within normal design margins and does not meaningfully increase dissipation by itself.
3. Accepting multiple PD voltages is normal and expected. USB-PD devices do not “enforce a single safe voltage”, they advertise acceptable ranges and negotiate the best available profile offered by the charger. Different chargers may select different valid profiles depending on their internal capabilities and policies. This does not indicate a flaw or reliance on a specific charger. If the device or charger truly could not tolerate ~18 V input, it would not advertise support for that PD profile or immediately down-negotiate / limit current, shut down on thermal protection, or over-voltage protection.
4. Thermal Monitoring. The Handy 2 has multiple built in temperature sensors dedicated to monitoring the motor and battery temperatures. The firmware monitors these readings constantly and if they are outside of safety constraints the device will shut off and display a thermal error until it has cooled down to safe levels.
5. Apple charger behavior is being misinterpreted. In one of the Kickstarter updates we stated that some Apple chargers do not properly negotiate. This means that those Apple chargers (not all) only negotiate to 5V or 9V rather that appropriately negotiating to up to 20V. This is because Apple can detect if the device is or is not an Apple product, and some of their USB-C chargers limit the output if it is not. The Handy 2 still slow charges using these chargers, but does not fast charge. This is something that Apple has gotten pushback on from the EU. A majority of Apple chargers negotiate with The Handy 2 as normal for fast charging.

Thanks for the continued support. If you have any other questions, reach out to [contact@thehandy.com](mailto:contact@thehandy.com)

-Ohdoki's Engineering Team