APC wants ~1600 CZK for their proprietary cable to connect APC BackUPS CS 500. It has RJ50 connector in back and quick google shows it is, among other things, just plain USB. So time to go shopping.

I found DELOCK 80205 cable assembly where RJ50 is already crimped to 1m of cable since I don’t have tools to crimpt 10p10c RJ. To other end I am going to use GOOBAY 12025 USB-A plug. And we are going to use this wiring guide.

Wiring we are going to do:

APC Pin USB Pin Description
1 1 USB +5V (red wire)
4 shield chassis ground
7 4 USB GND (black wire)
9 2 USB Data- (white wire)
10 3 USB Data+ (green wire)

And for sake of completness, full pinout from APC Back-UPS CS 500 manual

UPS Pin UPS signal Description
1 USB_VCC decoupled with a ferrite, and protected with a 6.2V zener on the PCB side
2 ON_BATT (active high) - Logic 1: 12V via 3kohm resistor, Logic 0: 0V via open collector of 2N2222 to gound
3 \Lo_BATT (active low) - Logic 1: 12V via 3kohm resistor, Logic 0: 0V via open collector of 2N2222 to gound
4 GND direct connection, no decoupling
5,6 USB TST (NC) No physical connection
7 GND decoupling via ferrite
8 INVSD Active high to base of a 2N2222 (resistor input -> base: 3kohms, resistor base -> gnd: 1kohms)
9 USB Data- (negative) Protected with 47ohms resistors, ferrite
10 USB Data+ (positive) Protected with 47ohms resistors, ferrite

So if we put it all together, this is cable we want.

And it works like a charm.

Config my NUT gave me is this:

[apc500]
        driver = "usbhid-ups"
        port = "auto"
        vendorid = "051D"
        productid = "0002"
        product = "Back-UPS CS 500 FW:808.q8.I USB FW:q8"
        serial = "REDACTED"
        vendor = "American Power Conversion"
        bus = "001"
        device = "004"
        busport = "008"

and with that it shows everything I need. Job well done.