Modifying an existing camper with very little space

Been lurking on a few threads about tight installs lately and it's got me thinking about my own situation — retrofitting into an existing camper where the previous owner already had a Sargent EC176 system in place.

The Sargent is doing some things fine but I want to properly upgrade around it rather than rip it all out. Has anyone integrated Victron kit alongside an existing Sargent setup without binning the whole thing? Specifically wondering about:

• Keeping the Sargent for basic 12v distribution while letting Victron handle the heavy lifting
• Whether a Cerbo GX can meaningfully monitor a system where part of the wiring is "foreign" to it
• Fitting a Multiplus II 12v 3kVA under a bench seat — there's barely 400mm of height to play with

The space issue is real. Everything has to go in a compartment that's probably 600mm wide by about 500mm deep. I've seen people squeeze a lot in but I'm not sure I've seen it done around an existing proprietary system rather than starting fresh.

Also curious whether the Orion XS is worth it over the older Orion-Tr Smart for a van that's primarily weekend use — is the faster charge rate actually useful if you're rarely doing long drives?

Would love to see photos if anyone's done something similar in a confined space. Diagrams welcome too — even rough ones.

@VoltVicky the Sargent systems are a right pain to work around — been there with a static caravan build. The EC176 in particular hogs a lot of the logical control, so you're fighting it if you try to bolt on a proper Victron setup alongside it.

Honestly the question is whether you keep Sargent doing the 12V habitation stuff and just add solar/monitoring separately, or rip it out entirely. Depends how much of the original wiring you trust.

What's your battery situation — still on the original leisure battery or are you looking at upgrading to lithium? That changes the conversation quite a bit because the Sargent charge management wasn't designed with LiFePO4 in mind and can cause problems.

Space-wise, a Victron SmartShunt tucked inline somewhere buys you proper monitoring without needing much room at all.

@VoltVicky spent three weekends swearing at a Sargent system in my van before I ripped the whole lot out and replaced it with a Victron setup — best decision I ever made, second only to buying decent cable crimpers.

@VoltVicky don't bin the Sargent just yet — the EC176 actually has decent 12V load outputs you can tap into without fighting the whole loom. What I'd seriously look at is wedging a Victron BMV-712 in somewhere; even in a cramped install the Bluetooth monitoring means you're not needing a dedicated display panel taking up precious space.

On my narrowboat I ran into similar grief — existing 12V wiring everywhere, no logical plan, previous owner's "creative" fusing. Ended up mapping every circuit before touching anything. Tedious but saved me properly.

Key question for your specific situation — do you know what battery chemistry the previous owner was running? Because the EC176 charge profile settings matter a lot if you're planning to drop in lithium (Fogstar Drift cells are popular right now and reasonably priced).

@Boycie makes a fair point about the load outputs, though in my experience the EC176's charge management is where it starts falling over once you add any decent solar capacity — it's simply not designed with lithium or larger arrays in mind.

Had a similar headache retrofitting a Fogstar lithium bank into a shepherd's hut build. Ended up running the Sargent purely for 240V hookup management and routing my solar through a separate Victron MPPT entirely. Two parallel systems, yes, but it kept the existing wiring intact and gave me proper BMS-aware charging.

Worth asking: what's your battery chemistry and approximate panel wattage? That changes the answer considerably. If you're staying with lead-acid and modest solar, @Boycie's approach is probably fine. Go lithium or beyond ~200W and I'd seriously consider isolating the solar side from the Sargent entirely.