Smart BMS 12/200 in Ford eTransit

Interesting situation has come up with a friend's Transit Custom conversion that I thought worth raising here, because I've been mulling something similar for my boat.

He's running a Victron Smart Lithium 12/200 with the Smart BMS 12/200, and wants to feed a third-party sine wave inverter from it — not a Victron MultiPlus. The BMS load disconnect output is obviously sized for the job in terms of continuous current, but the question is how cleanly it handles the inrush when a chunky inverter initialises. Some inverters pull a fairly savage spike on startup, and I'm not convinced the BMS load disconnect is designed to absorb that repeatedly without degrading over time.

On the boat I've been considering doing something similar — Fogstar Drift 200Ah paired with a Victron SmartShunt and a non-Victron inverter (budget being what it is). The BMS question is where I keep stalling.

Has anyone here actually run a third-party inverter — say a Renogy or Giandel unit — directly off the BMS 12/200 load output rather than switching it via a separate contactor or relay? Or is the sensible approach to use the BMS's load disconnect signal to trigger an external relay, keeping the high-current path separate from the BMS's own switching circuitry?

Feels like it should work but I'd rather hear from someone who's done it long-term rather than fry a BMS finding out. The Victron documentation is characteristically thorough but doesn't really address third-party inverter inrush specifically.

Any real-world experience welcome, particularly from van or marine installs where space makes a tidy solution important.

@DougPearce you've cut off mid-sentence there — "Smart Li..." what exactly? The Smart Lithium 200Ah, or the Smart BMS 12/200 controlling something else entirely? Makes a difference because the 12/200 has that rather infamous load output current limit that catches people out when they're running inverters directly off it rather than through a separate DC bus.

The eTransit alternator situation is also worth flagging — Ford's variable-voltage smart alternator will absolutely confuse a standard MPPT or DC-DC charger unless he's got a proper Orion-Tr Smart in there. Victron's done some firmware work on this but it's still not entirely painless.

Finish your sentence and let's dig in properly — boat applications have some overlapping quirks (damp, vibration, bilge pump loads) so genuinely curious where this is heading.

@DougPearce yeah you've left us hanging there mate — need the full setup before anyone can give useful advice. Smart BMS 12/200 and Smart Lithium are quite different beasts in terms of how they handle load disconnect events.

That said, I ran into something nasty on my boat last autumn with a Smart BMS 12/200 paired to a 200Ah Victron Smart Lithium. The BMS tripped under heavy inverter load and took the alternator circuit with it — nearly cooked the diode pack on a Beta Marine. Turned out the load disconnect wasn't being handled gracefully because the pre-charge resistor wasn't properly spec'd for the cable run length.

What's his alternator situation in the Transit? That's usually where these installs get interesting.

@DougPearce yeah the post got chopped, need the full details before this goes anywhere useful. What's the actual issue you've hit — is it a comms problem between the BMS and the inverter/charger, or something physical with the install?

Asking because I had a nightmare with my garden office setup getting the Smart BMS talking nicely to a MultiPlus — turned out to be a dodgy VE.Bus cable rather than anything clever. Sometimes it's the boring stuff.

@DougPearce looks like your post got truncated — we're all working blind here until you can edit or repost the full setup details.

That said, the Smart BMS 12/200 is a fairly specific bit of kit with some well-known quirks worth flagging now regardless:

• It's designed to work with Victron's own Smart Lithium batteries specifically — pairing it with third-party cells (Fogstar, EVE, etc.) is unsupported and can cause load-disconnect headaches
• The 12/200 load output rating is often misunderstood; that's continuous, but inrush on inverters can trip it
• In a Transit Custom the alternator charging interaction via the BMS is worth scrutinising carefully — you'll want a proper DC-DC charger (Orion-Tr Smart) in the loop

Running something similar on my narrowboat so genuinely interested to hear the full scenario once you've recovered the rest of that post.

@DougPearce while we wait for the full post, worth flagging that the Smart BMS 12/200 has a few known quirks in vehicle installations specifically — the alternator interaction via the Cyrix-Li-ct is the usual culprit. The 200A continuous rating also gets derated significantly once ambient temps climb inside a van bodywork in summer. If your friend's setup includes a DC-DC charger (Orion-Tr Smart being the sensible choice here) rather than direct alternator feed, that changes the troubleshooting entirely.

Also curious whether this is a Fogstar or CATL cell pack, as the BMS communication behaves differently depending on cell chemistry reporting. Post the full config when you can — specifically the load disconnect behaviour and whether he's seeing this under charge, discharge, or both.