Hey all,
Looking at installing this 20A DC DC/MPPT combo in my van:
www.h2r-equipements.com
And I'm wondering if instead of wiring it as the manual suggests with a negative cable going all the way back to the engine battery:

I could do the following instead to simplify the wiring and save on cable:

With the ground from the house battery going to a metal part of the van body on the interior right next to the house battery (scraping the paint to make good contact).
Would this have the same result and work properly/be safe?
Thanks
Looking at installing this 20A DC DC/MPPT combo in my van:

Chargeur DC-DC BOOST 20 MPPT ENERGIE MOBILE pour van et bateau - H2R Equipements
Le chargeur DC-DC BOOST 20 MPPT est idéal pour recharger votre batterie auxiliaire 12V depuis un alternateur ou un panneau solaire. Parfait pour les vans, camping-cars et bateaux, compatible avec toutes les technologies de batterie.
And I'm wondering if instead of wiring it as the manual suggests with a negative cable going all the way back to the engine battery:

I could do the following instead to simplify the wiring and save on cable:

With the ground from the house battery going to a metal part of the van body on the interior right next to the house battery (scraping the paint to make good contact).
Would this have the same result and work properly/be safe?
Thanks