As Derek says above, the cable to use is Welding cable available in many sizes & a lot cheaper than £8 something a metre.
https://www.amazon.co.uk/Welding-Cable-B...B00E1TN602
Available a lot cheaper still from a decent wholesaler.
https://www.amazon.co.uk/Welding-Cable-B...B00E1TN602
Available a lot cheaper still from a decent wholesaler.