System designs app

Been thinking about this after helping a mate plan his narrowboat refit last month — we spent ages manually cross-referencing Victron datasheets, cable sizing tables, and voltage drop calculators across three different browser tabs. There has to be a better way.

Victron's own VictronConnect is brilliant for commissioning and monitoring, but it's not really a design tool. The closest thing I've found is Victron's wiring unlimited PDF combined with their online product selector, but neither actually generates a wiring diagram or validates your cable runs against load.

A few options worth exploring:

• Solar Sizing Calculator (various) — Renogy and a few others have basic web tools, but they're obviously geared toward pushing their own kit
• DIY Solar Power Forum's calculators — reasonable for rough sizing but no diagram output
• Figma/draw.io with custom Victron symbol libraries — what I ended up doing for my shepherd's hut build, genuinely tedious but thorough

What I'd actually want is something that lets you drop in a SmartSolar MPPT, Multiplus, Orion-Tr DC-DC, and battery bank, then spits out recommended cable gauges, fuse ratings, and a proper schematic. Fogstar Drift cells have different charge profiles to drop-in LiFePO4 units so it'd need to handle that nuance too.

Does anyone know if Victron are developing anything like this properly, or is there a third-party tool specifically for 12V/24V off-grid systems that I've missed? Particularly interested if it handles both solar input and alternator charging simultaneously, which is the reality for most boats.

@LH_Marine mate, I feel this in my soul 😂 Spent three evenings last winter with seventeen browser tabs open, a notepad covered in scribbles that looked like I'd let a spider walk through ink, and a Victron datasheet that somehow contradicted itself on page 4.

What we really need is an app where you dump in your

@LH_Marine seventeen browser tabs is rookie numbers — I had 34 open once planning my garden office install, crashed Chrome, lost the lot, and had to start again. Nearly cried.

Anyway. Yes, a proper integrated tool would be genuinely useful. The real gap I see is cable sizing tied directly to your actual component selections — not some generic calculator

@LH_Marine the core problem with most "system design" tools I've encountered is they treat component selection as the hard part, when actually it's the interdependencies that kill you — change your battery bank voltage and suddenly your cable sizing, fuse ratings, MPPT selection, and inverter compatibility all cascade simultaneously.

What I'd actually want from such an app is constraint propagation — you modify one parameter and it flags every downstream consequence rather than just recalculating silently. Victron's own VictronConnect does some of this but only once you're already committed to their ecosystem.

For my cabin backup system I still maintain a spreadsheet with linked cells precisely because no app handles the UK-specific bits properly — G98/G99 compliance considerations, realistic UK irradiance figures rather than optimistic Mediterranean assumptions, and actual Fogstar/Pylontech BMS communication constraints.

The tool gap is real, but I'd be sceptical anything properly solves the interdependency problem without essentially being a full expert system.

@BrianBrown 34 tabs AND a crashed Chrome — that's not system design, that's a cry for help 😂

Honestly though, what I'd kill for is something that just knows the Fogstar Drift 200Ah won't play nicely with a certain BMS config before I've already ordered it — learned that the hard way with my static van setup. Real-world component compatibility warnings, not just "check manufacturer datasheet" which is basically telling me to go read War and Peace in Welsh.

If someone built a tool that combined proper UK cable sizing regs, live component compatibility flags, and actual voltage drop calcs in one place I'd pay actual money for it — and I say that as someone who considers "free" a personality trait.