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I keep a NOCO GB40 1,000 Amp Jump Starter with the compact spare tire in case I need to jump start the battery.
It occurred to me that the best way to ensure that the NOCO GB40 is always fully charged is to connect its charging cable to a switched USB outlet in the trunk. Jaguar used to make an Auxiliary Power Socket kit (part number C2A1403, discontinued) and I used the installation instructions, with modifications, to install a dual USB-A socket.
Specifically, I used the following parts to make Part A in the diagram. I also used a Powerwerx panel mount dual USB QC 3.0 device charger ($27.99, https://powerwerx.com/panel-dual-usb-qc30-charger) in lieu of the “cigar lighter” outlet (Part B). (I did not need parts C, D, and E.)
1. Disconnect the cable from the positive terminal of the battery.
2. Unscrew two wingnuts and remove plastic covering over right rear taillight
3. Remove gray felt panel on right side of trunk
4. Using a box cutter, cut hole for USB charger in panel (to left of openings for CD changer and navi disk player).
5. Insert USB charger through trunk side of panel and secure using threaded ring.
6. Take 3’ length of 2-conductor cable and, beginning about 6” from one end, carefully make a 6” incision in outer black plastic covering.
7. Pull red wire out through the incision and remove a section sufficiently long to accommodate insertion of inline blade fuse holder; strip ˝” of plastic off of each end.
8. Cut fuse holder wire and strip ˝” of plastic off each end; solder each end to corresponding part of cut wire in 2-conductor cable. Wrap bare wire in electrical tape. Use electrical tape to close incision in 2-conductor cable.
9. Insert 10 amp fuse in holder and close protective cover.
10. Strip Ľ” of plastic off of red and black wires at both ends of 3’ cable. Use crimping tool to (a) attach blue female connectors (included with USB charger) to end closest to fuse holder and (b) male connectors to other end.
11. Identify three-wire, black plastic accessory connector near battery (see photo). Using wire cutters, remove plastic connector.
12. Strip Ľ” of plastic off of black (ground) wire and red/white (ignition switched) wire; use crimping tool to attach yellow female connectors to both wires. Connect female connectors to male connectors (red/white to red, black to black) on 3’ cable.
13. Connect blue female connectors on other end of 3’ cable to prongs on USB charger (red to + , black to — ).
14. Remove top of trunk fuse box and confirm that there is a brown relay in the “R6” position and a 20 amp fuse in F11; if not, you will need to purchase and insert them. Replace top of fuse box.
15. Test connection: re-attach cable to battery, insert USB cable with connected device into charger, turn on ignition. Confirm that device is charging. Turn off ignition, disconnect USB cable.
16. Re-attach gray felt panel, re-install black plastic covering over right rear taillights.
17. To charge NOCO GB40 unit while ignition is on, I cut a small hole closest to the USB-C charging port in the NOCO carrying case, inserted the charging cable through the hole, and connected the USB-C connector to the NOCO unit. I ran the charging cable across the battery and plugged the USB-A connector into the charger, then carefully replaced the battery cover as shown in the photo.