Is this system still safe?

Had a similar panic last year when Renogy quietly updated the specs on my 400W panels mid-build — suddenly my Voc calculations were looking a bit spicy for the Victron SmartSolar I'd already bought.

The bit that catches people out is temperature-corrected Voc — on a cold Scottish morning (not that I'm in Scotland, but you get me) those open-circuit voltages climb nastily, and if the updated datasheet has shifted even slightly, you could theoretically be nudging your controller's absolute maximum input.

Key things I'd check if the datasheet changed:

• New Voc — run it through the temperature correction at your local record low (-10°C to be safe for most of the UK)
• New Isc — does it still sit comfortably within your charge controller's rated input current?
• String configuration — if you've got panels in series, small Voc changes stack up fast

For the Victron Multi RS specifically, I believe the PV input limit is 680V — sounds generous until you've got a long string on a crisp February morning.

Worth firing your updated figures into Victron's MPPT calculator online, it'll flag any issues pretty quickly without the guesswork.

Anyone else had a manufacturer quietly shift their datasheets and only noticed halfway through an install? Feels like a rite of passage at this point. 🔆

@SamFrost73 classic Renogy move that — their datasheets have been known to shift between production batches too, not just spec updates.

Key thing to check: your MPPT's absolute maximum input voltage, not just the rated voltage. On most Victron SmartSolars that's 150V (some 100V models exist, easy to mix up). Then calculate your worst-case Voc — that means panels in series at -10°C using the temperature coefficient on the datasheet. UK mornings in January will get you there.

If you're within 10-15% of that absolute max, I'd be having a serious think. Victron's own sizing calculator is worth running. I did exactly this on my narrowboat build — ended up rewiring two panels from series to parallel just to keep comfortable headroom. Bit annoying but better than a fried controller.

@SamFrost73 been there with the motorhome build — spent a weekend rechecking every Voc figure after a Renogy datasheet discrepancy nearly put me over my SmartSolar's 150V input limit. The thing people forget is that Voc climbs as temperature drops, so even if your summer numbers look fine, a crisp January morning in Scotland could push you right to the edge. I now run everything through Victron's MPPT calculator with the lowest recorded temp for my area plugged in, not just the standard -10°C. Adds maybe 8-10% headroom to whatever the datasheet says. If you're already borderline on the existing specs, I'd honestly consider rewiring to a slightly lower string voltage rather than hoping for the best.

@SamFrost73 worth remembering that Victron's MPPT input voltage limits are absolute maximums, not "soft" limits with any headroom built in. The SmartSolar 100/30 is hard-capped at 100V, and that's before you factor in the UK cold-morning worst case — a clear January dawn at say -10°C can push Voc 8-12% above the STC figure. I learned this the hard way before I even switched the system on; rechecked everything against the Victron wiring unlimited calculator with the temperature coefficient from the actual datasheet. If Renogy have shifted specs between batches as @ExSquaddie49 suggests, I'd be pulling the physical label off the panels themselves and cross-referencing against whatever batch/serial documentation you can dig out. The printed label Voc sometimes differs from the marketing datasheet too. Don't trust a single source on this one.

@LesWood78 makes a solid point — worth adding that the Voc figure on the datasheet is measured at STC (25°C cell temp), which you'll basically never see in UK conditions. Cold clear mornings in January are where it gets interesting; cell temps can drop well below that, pushing Voc higher than the rated figure. Standard practice is to derate using the temperature coefficient and your lowest expected ambient — most people use around -10°C as a reasonable UK worst case. Run those numbers before assuming you're safe. On my narrowboat I leave a deliberate headroom of at least 10% below the controller's absolute max for exactly this reason.