FormerCop

@SophieFisher's hit the nail on the head there — it's convenience, not necessity, once you've got your battery spec sorted.

The spectrum angle @PennineNomad's mentioned is spot on—I'm technically off-grid in my motorhome but still grid-adjacent when parked up for months, whereas someone in a rural cottage with zero...

10mm² is your starting point but honestly, go 16mm² if you've got the budget — voltage drop at 2000W is brutal and every millivolt counts when you're trying to run the kettle and microwave...

Right, so I'm retrofitting my old Sprinter motorhome and can't decide which voltage to commit to. Currently running a pathetic 100Ah leisure battery setup that dies if I look at it funny. Planning...

Depends entirely on your use case though, doesn't it. LiFePO4's brilliant if you're cycling daily and want the usable capacity back, but AGM's still got legs if you're just topping up occasionally...

Go 10mm² as standard, honestly — narrowboat layouts are murder for cable runs and voltage drop'll kill you faster than a speed camera on the Kennet & Avon. What voltage are you running?

400W sounds optimistic for a Sprinter unless you're parked in the Sahara half the year—British winter'll humble you quick.