Hey everyone! I've got an Ossur Rheo knee that I absolutely love, but I've been running into battery life issues since I'm quite active. It typically lasts 1.5 to 2 days, but when I'm out camping or at festivals, I often find myself without access to AC power for longer. The knee charges using a 24V, 1.25A barrel plug.
I'm curious if anyone can help me figure out how to charge this with a USB PD 3.1 power bank, which can supply 20V or 28V. My plan includes:
- A microcontroller to handle the USB PD protocol and request the right voltage.
- A voltage converter to up the voltage to 24V while adjusting the amperage to 1.25A.
- Figuring out the barrel plug specs for the connection.
- Gathering wiring materials, a soldering iron, and a multimeter for safety checks.
I found a potential product on Amazon that looks promising for this purpose. But since my background is more in DevOps and software, I'm a bit lost on the hardware side. Any expert opinions or suggestions would be greatly appreciated! Cheers!
5 Answers
Honestly, I’d recommend reaching out to Ossur for the official word on whether you can directly charge your knee with a USB PD 3.1 power bank. As an engineer with 20 years in the field, I advise against making any modifications to medical devices unless you’re 100% clear on the risks. Safety should come first—imagine if a voltage converter went haywire and pumped too much voltage into your knee!
Check the label on your current charger. Is it a smart one? If the device handles voltage and current regulation, you might get away with just supplying 24V and the required amperage without any fancy modifications.
You should definitely consider buying a dedicated battery charger designed for your device type instead of a DIY solution. Look into chargers that are compatible with lithium batteries if that's what your knee uses. They should be able to handle diverse power inputs and come with safety features, which is crucial for anything battery-related!
If you can get 28V from your power bank, that's actually easier to bring down to 24V than trying to boost 20V up. But make sure to look for the voltage limit on your knee; you could probably stick with 24V if the device's circuitry is designed for that. Remember, as long as your power supply can provide at least 1.25A, you're golden!
First off, you're right about the amperage—you don't need to reduce it. Just make sure you hit that 24V requirement and your knee will pull only what it needs, in this case, 1.25A. Also, double-check the center polarity of the barrel plug to avoid any mishaps!