USB C PD to Step up converter for charging... basically no voltage output?

I’ve got this usb pd decoy. When plugged in, it works perfectly, handshakes and outputs 20V when set to that voltage.

I have a 10s battery, so I need a step up converter to get that 20V to 42V, so I bought this.

As soon as the converter is wired into the decoy, beds get shat :frowning: if the decoy is set to anything other than 5V, no voltage is output from the decoy at all. If I set the decoy to 5V, about 4.8V are outputted from the decoy and then the converter does its thing (seems to be set at 14ishV). It’s not meant to take less than 10V and it gets hella hot so it’s all a bit strange…

Anyone know what the heck is going on? Why’s the buck fucking up the decoy? Gonna plug the buck into a car battery tomorrow and see what it does from that, but figured I’d get a headstart on some hopeful responses here tonight :slight_smile:

I was having a similar issue using a USB C PD decoy and a boost converter. I found it worked when I disconnected the output of the boost converter from the battery, plugged in the charger, and reconnected the output. I also had to ensure that the Constant current was set a little below the maximum output of a charger otherwise the PD board would stop working. I was able to dial this in using a multimeter and my BMS, setting the charging current to around 2.2 amps for a 10s setup to stay under the 100watts of my USB C charger. ( In practice I achieved this by switching the BMS charge and discharge switch off, plugging in charger, and then enabling charge switch) (I have one of those Bluetooth smart BMS things) The boost converter I used: 600W Constant Current Boost Converter DC- DC 10V-60V to 12-60V 10A Adjustable Step Up Voltage Regulator CC CV Power Supply Module (a number of them on amazon) I recommend covering it in epoxy because the big coil and CV and CC adjusters are fragile, especially with vibrations (as it was mounted in my board) and I had a massive heatsink keeping it cool because otherwise it will cook itself. Your board looks different than mine (no barrel connecter and mine was smaller) but perhaps you are facing a similar issue.