SolarSense 750 calculation / setting

Just fitted a SolarSense 750 to my shepherd's hut array this weekend — mounted it between two of the 200W panels using an end clamp, which worked a treat once I'd bodged together a decent bracket (that bit definitely needs to be in the manual, just saying).

Anyway, I've got it talking to my Victron Cerbo GX via the VE.Direct cable and the readings are coming through, but I'm scratching my head over how it actually calculates the active power figure it's reporting.

My setup is two strings running into a SmartSolar MPPT 100/30, and what I'm seeing on the SolarSense doesn't always line up with what the Victron app is telling me — particularly on broken cloud days like we've had up here recently. Sometimes the SolarSense is reading noticeably higher, which makes me wonder if it's measuring irradiance and then estimating output based on panel spec, rather than reading actual harvested watts?

A few specific questions:

• Does it calculate from irradiance × panel rated output, or is it pulling real current/voltage data somewhere?
• Is there a calibration step I've missed? The quick-start guide is a bit thin on detail.
• Does panel orientation feed into the calculation, or do you just point the sensor and let it get on with it?

I've hunted through the PDF manual and had a good root around on here, but couldn't find a clear explanation. Would love to understand what's happening under the hood before I start trusting it to inform any battery charging decisions — especially heading into autumn when every watt counts on the narrowboat over winter.

Nice one @HazelDawn, shepherd's hut setups are great fun to get right!

One thing worth double-checking with the SolarSense 750 — make sure you've configured the battery type correctly in the settings menu before you start relying on the readings. The default from factory is often set to flooded lead-acid, so if you're running lithium or AGM you'll want to adjust that, otherwise the state-of-charge calculations will be well off.

Also, given it's mounted between panels, keep an eye on operating temperatures in summer — the 750 can get a bit warm in direct sun and thermal drift can affect accuracy slightly. Not a dealbreaker, just worth knowing.

What battery bank are you running with it? That might help if you've got any questions about calibrating the shunt properly. 🙂

@HazelDawn welcome to the forum! Shepherd's hut builds are a lovely project to cut your teeth on.

Quick practical note since you mentioned the bracket bodge — worth making sure the SolarSense 750 has decent airflow around it. They can throttle output if they get too warm sandwiched tightly between panels. Bit of a gap underneath makes a real difference in summer.

Also, what battery bank are you running? The 750's absorption/float settings will need dialling in correctly depending on whether you're on lithium or lead-acid — the defaults are quite conservative and often worth adjusting once you know your chemistry.

@HazelDawn one thing I'd flag that often gets overlooked on small arrays like yours — make sure your SolarSense 750 settings account for the actual installed tilt angle and azimuth deviation from true south, not just magnetic south. Compass deviation in the UK runs roughly 1–3° west depending on your location, which sounds trivial but compounds with shading calculations.

Also worth logging your Voc at different ambient temperatures early on; the 750's compensation algorithm needs accurate baseline data or its yield predictions drift noticeably over time. I spent an embarrassing number of hours chasing a discrepancy on my cabin setup before realising I'd fed it the panel datasheet Voc rather than my actual measured cold-morning figure.

What charge controller are you running alongside it? That'll affect how useful the 750's output actually is in practice.

Good point from @Paddy on the settings side of things. One thing I'd add that's bitten me before on my narrowboat array — double-check your cable sizing between the SolarSense 750 and the charge controller. Undersized cable introduces voltage drop that the unit can misread as a genuine array performance issue, which then throws off your calculations.

On the shepherd's hut specifically, depending on how exposed the site is, shading from the roof pitch at low winter sun angles can really skew the baseline figures you're working from. Worth logging a few days of data before you start tweaking settings — gives you something concrete to compare against rather than chasing your tail.

What charge controller are you running downstream? Victron SmartSolar will let you cross-reference the SolarSense data fairly easily through VictronConnect.

Nothing says "weekend well spent" than dangling off a shepherd's hut roof arguing with an end clamp while your neighbours think you've finally lost it — been there with my van conversion and the bruised knuckles to prove it.

Worth double-checking your temperature compensation setting on the 750 if you're out in the Cotswolds this time of year — a cold clear November morning will have your panels outputting noticeably higher voltage than the standard 25°C STC figure, and if your SolarSense is feeding data to a Victron MPPT it can throw your logged figures off enough to matter.