+Terminal voltage on J2, 3 volts on J1

[isibbotson]

I got my serial adapter and logic level shifter hooked up according to the diagram, then figured out using python on Linux. I can talk to the adapter and run commands, but they return with "read_id: Failed with error: [Errno 5] Input/output error"

I used the ATNSINC serial adapter that a few people have had plug-and-play success with, and then used a SparkFun level shifter(https://www.amazon.com/dp/B088FYQJYZ?ref=ppx_yo2ov_dt_b_fed_asin_title).

I checked my J1 and J2 voltage as I said in the title. 15 volts (known dead cell) on J2, and 2.5-3 volts on J1

I have the + and - leads on the battery hooked up to the shifter HV and GND terminals with nothing else hooked up, I get 15 volts on HV2. If I plug in the lead from HV2 into J2, the battery puts 4 volts to J1. This is with the serial adapter disconnected. I also get 10k Ohms between HV and HV2.

I'm having a hard time determining if putting HV voltage to HV2 is normal behavior for a level shifter. I'm leaning toward a faulty/incorrect level shifter but it would be another 3 day wait to just get another one, so if there is a different fix that could save me some time that would be extremely helpful