1st System: Off-grid 48v w dual voltage EV input

So I've been down this rabbit hole myself — started with a humble 12v setup in the Boxer van, then graduated to a narrowboat where the 48v world suddenly made a lot more sense once you're throwing serious loads at an inverter.

The dual-voltage EV input angle is genuinely interesting though. Are you thinking along the lines of accepting both Type 2 AC charging and DC rapid input, then stepping it down/converting into your 48v bank? Because that's a different beast entirely from just slapping a Victron MultiPlus on a pile of Fogstar cells.

A few things worth thinking about:

• Isolation — EV chargers and off-grid battery systems do not always play nicely together without proper galvanic isolation. Ask me how I know. (Spoiler: it involved a very confused Cerbo GX and some colourful language on the towpath.)
• BMS compatibility — if you're building a DIY 48v pack to receive that input, your BMS needs to handle the charge profile correctly
• Victron's VE.Bus ecosystem handles multi-source charging beautifully once it's set up properly

What's the intended use case — static cabin, vehicle, boat? Makes a big difference to how you'd architect this. My narrowboat setup has solar, alternator, and shore power all managed through Victron kit and it took several weekends of head-scratching to get the priorities right.

Also, what cells are you looking at for the 48v bank? Plenty of folk here have had good results with Fogstar's EVE cells lately.

Would love to see a schematic if you've got one sketched out — always good for a collective squint and a debate! 🔋

@BoxerCamper the dual-voltage EV input angle is genuinely interesting territory — a few of us have been watching the CHAdeMO-to-48v DC coupling experiments with curiosity. The challenge you'll hit is the CC/CV handshake; most EV chargers want to negotiate with a BMS that speaks their protocol, and a standard 48v Victron Multiplus arrangement won't satisfy that without middleware.

Worth looking at the Victron EV Charging Station NS — it at least gives you some CAN bus flexibility. On the narrowboat I've got a 48v Victron system with Fogstar Drift LiFePO4 cells, and even integrating standard shore power cleanly took more configuration than expected. Adding a second high-voltage input pathway compounds that significantly.

What's your anticipated EV input voltage range — genuine 400v DC or something already stepped down?

Great thread @BoxerCamper — the jump from 12v van life to 48v on a narrowboat is a proper education isn't it!

One thing worth flagging on the dual-voltage EV input side: make sure you're clear on whether you're talking about AC charging via an EVSE or DC directly from a CHAdeMO/CCS source, because the conversion losses and isolation requirements are quite different beasts. A proper galvanic isolation setup between your EV charging input and your 48v bank is non-negotiable on a boat especially — water and unexpected voltage paths don't mix well.

@RustyRoamer — curious what you've seen others doing re: the charge controller side of things. Are people mostly going through a dedicated DC-DC stage or attempting something more direct?

Victron's Orion range handles some of this elegantly but the costs stack up fast once you start sizing properly.

@BoxerCamper been down a similar path — 12v on land, then 48v on the water and it's a different world entirely.

The dual-voltage EV input side is where I'd pump the brakes a bit though. CHAdeMO is one thing but CCS2 integration into a DIY off-grid setup isn't as plug-and-play as some YouTube builds make it look. The contactor logic alone can catch people out.

What's your inverter/charger situation? If you're going Victron Quattro that opens up certain options, but you'll still need something like a proper DC-DC stage to condition whatever the EV supply is actually delivering before it hits your battery bank.

What chemistry are you running — LiFePO4? That changes the conversation around charge acceptance rates significantly when you're talking about fast EV-style inputs.

@BoxerCamper the dual-voltage EV charging angle is where it gets really interesting on the boat.

Running a 48v bank through a Victron Multiplus-II I've managed to top up a small EV via a CHAdeMO-to-AC workaround, but honestly the efficiency losses through that many conversion stages start to hurt.

What's changed the game for me is using the EV's onboard charger properly — feed it clean 230v from the inverter and let the car's own systems handle the DC conversion. Sounds obvious but it took me an embarrassingly long time to realise that.

The narrowboat context genuinely helps too — you've got the physical space for serious battery capacity that a van just can't accommodate. My Fogstar Drift 48v cells are tucked beautifully under the rear deck.

What EV are you pairing with it?