Hi Barrie and
to the forum.
You didn't say where you purchased this battery from, but you will need to contact your supplier to agree on a practical solution.
I suspect that returning the battery is likely to be very expensive, therefore the most obvious solution would be to modify the existing wiring to incorporate the switch as I've shown below:
Although this particular switch is typically installed into the positive cable, the battery case is fully isolated
and the battery's
BMS also switches the negative side of the battery circuit to prevent over current and over discharging, therefore the key switch will work just as effectively installed on the negative cable
(as shown in the modified photo) which seemed to be the neatest and most convenient option in this instance.
You would simply cut the existing black wire approximately 2 inches from the Anderson connector leaving enough cable to allow it to be soldered onto the nearest switch contact.
You would then have to extend the remaining black wire coming from the battery using a few inches of suitable gauge wire soldered between the original wire and the other switch terminal.
The soldered wire joint would need to be safely insulated using either heat shrink tubing or insulation tape.
Unfortunately, I suspect a heavy duty soldering iron will be required to produce enough heat to solder the thick wires onto the switch contacts, so you may need to find someone locally who is able to do this for you and then
(hopefully) reclaim any expenses incurred from your battery supplier.
Alan