We use 16mm ho7 rubber cable at work for 63amp cables so think you have the wrong size. 4mm is for 32amp so check the specs on HO7 rubber cable, depending on temperature you may need artic flex?
The aim is not to modify my drill or my drill batteries in any way, just to provide an extender so you can - optionally - connect the drill and the battery via a cable (with the appropriate terminals at either end).
Do you have a feel for what difference it makes having the drill battery warmer in a ~0 degree environment?
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