? Dual Cellink Neo 8+ Installation

[Mark_D]

New member here. I am currently powering a Blackvue DR900X+ dash-cam from an ACC+ hard-wired Cellink Neo 8+ battery and all is working as it should. However, the parking time before low voltage shutdown is shorter than I would like. This is partly due to the relatively short periods that I typically drive so the battery pack often doesn’t reach more than 50% charge. Is there any reason why I shouldn’t hard-wire a second Cellink Neo8+ to my car and connect the battery packs together using a lead between the Battery Extension Sockets (+ve to +ve, -ve to -ve)? The first Cellink Neo 8+ would continue to supply the dash-cam. This should in theory double the combined maximum charging rate from my vehicle to 9A+9A=18A as well as doubling the potential battery capacity.

I have been advised by a UK distributer that connecting the 2 battery packs in this way would lead to a short circuit, but I can not see why connecting the packs in parallel in the same way as connecting a Cellink Battery Extension could cause this. He also told me that when a Cellink Neo 8+ is connected to an Extension Battery, the Neo is first charged to full capacity before the Extension Battery starts receiving a charge. I am doubtful that this is so as I am measuring a voltage across the Neo battery extension socket of 13.75v to 14.25v whether the Neo is fully charged or not and whether the ACC+ is on (engine running) or not.
Am I missing something here? Has anyone had experience of trying anything similar?