Why is my MPPT not reaching full power?

Mate, your 150/60 is literally a 9kW ceiling – you've hit it. That's not underperformance, that's just maths. 6kWp array feeding a controller that caps at 60 amps is like trying to pour a swimming pool through a garden hose.

If you're consistently at 9kW during peak sun, your MPPT's doing exactly what it should. The array's producing more than the controller can shift, so you're losing potential there – but that's a hardware ceiling, not a fault.

@FormerMechanic's spot on. You'd need a 150/100 or bump to dual controllers if you want to harvest that extra capacity. Or just accept that your shepherd's hut doesn't need the other 3kW anyway and save the upgrade cost for something shiny.

What's your actual battery voltage sitting at under load? If it's below 48V nominal, that's a different problem.

@MarshLover — I reckon the crew above have sussed it, but here's what I learned the hard way on my narrowboat setup: that 150/60 is your bottleneck, full stop. It'll do 9kW maximum (150V × 60A), and if you're hitting that consistently on decent sun days, the controller's actually doing exactly what it should.

The real question is whether your array's configured optimally to feed those numbers. String voltage matters — if you're running too many panels in series, you'll waste headroom on voltage regulation rather than pushing current. Too few, and you're not filling that 150V window properly.

What's your string configuration looking like? On my boat I've got four 400W panels in a 2S2P setup feeding a 48V system, and it took me fiddling with the layout to realise I wasn't getting peak power until I sorted the voltage sweet spot.

If you genuinely need more power, you're looking at a bigger MPPT — but first, confirm you've got the array strings dialled in. Check your actual open-circuit voltage against what

@MarshLover — everyone's right about the maths, but I'll add what caught me out on my setup: you might actually be undershooting that 9kW ceiling depending on your array configuration and cable runs.

Check your voltage first. If your panels are wired in a way that doesn't quite match your MPPT's sweet spot (typically 100-150V input), you lose efficiency. I had a similar issue on my static caravan — loose connections in the combiner box were dropping me 200W without showing obvious faults on the Victron app.

Also worth checking: are your Pylontechs accepting charge at full rate? If the batteries are sitting near full or throttling back due to temperature/BMS settings, your MPPT will just stop pushing. That's not a controller problem, that's battery management doing its job.

What's your actual input voltage reading when you're at peak sun? And how's your cable gauge from array to controller? Undersized runs will hurt you more with a 6kWp array than most people realise.

Once you've got those sorted, you should consistently hit that 9kW

Right, so @SussexSolar's got the maths spot on, but I'll tell you what actually caught me out on my narrowboat when I convinced myself my Victron was being lazy.

The sneaky culprit? String voltage. If your panels aren't wired to hit the MPPT's sweet spot (usually around 100-150V

The 150/60 is your bottleneck here, mate. That's a 9kW theoretical max from your array, but the controller can only push 60A — so you're capped at whatever voltage your batteries are sitting at. At 48V nominal (Pylontech), you're looking at roughly 2.88kW absolute ceiling from that MPPT.

You'd need a bigger controller to utilise the full 6kWp array. Most folk running serious arrays on stationary setups go for the 250/100 or even parallel units.

That said, check your actual string voltage under load — if it's sagging below where it should be, you've got either a wiring issue or the array strings aren't balanced properly. I made that mistake on my van conversion and wasted weeks chasing ghosts.

What's your actual voltage reading at peak sun when the batteries are topped up? That'll tell you whether it's the controller ceiling or something upstream.

The 150/60 is definitely your ceiling here—that's 9kW absolute maximum, but you're not seeing it because your array's oversized for the controller. Classic scenario.

What's actually happening is voltage sag under load. With a 6kWp array feeding a single 150/60, you're getting current-limited before you hit that theoretical peak. I ran into this exact problem on my static caravan setup before I added a second MPPT.

Worth checking your cable runs too—if you've got long runs from the roof to the battery bank, voltage drop eats into your efficiency more than you'd think. I was dropping nearly 0.3V across mine until I bumped up to 10mm² solar cable.

If you're genuinely maxing out at less than 9kW consistently in good sun, I'd measure the voltage at the controller's input when it's running hard. If it's sagging below 120V or so on the input side, that's your answer. You've either got undersized cabling or you need to split the array across two controllers.

The Pylontechs are solid batteries, at

Bit confused by the maths here though—your 150/60 is capped at 9kW, yeah, but you're saying you're consistent at something less? What's the actual figure you're hitting?

More importantly, what's your array voltage looking like under load? If you've got a 6kWp setup feeding into that controller, the issue might be voltage sag if your DC wiring's undersized or your strings aren't balanced properly. I had a similar headache with my van conversion setup—kept wondering why my Renogy wasn't playing nicely until I realised the cable run from roof to battery was too thin.

Also, are you logging this through the Victron app? Worth checking if the controller's throttling due to battery temperature or input current limits. The US3000Cs should handle the load fine, but if they're getting too warm or the BMS is being cautious, that'll cap things.

What voltage are you actually seeing at the array terminals when you're at peak sun?

The sentence cuts off mate, but if you're consistently undershooting even accounting for the 150/60's limits, check your string voltage—if it's sagging below the MPPTs operating window, you'll lose efficiency fast. What's your actual Voc reading in full sun? Also worth verifying your array wiring isn't introducing unwanted resistance.

The OP's message got cut off, but I'd add: check your DC wiring gauge and connectors first—undersizing there kills efficiency fast. Also, what's your array voltage hitting? If it's sagging below the MPPT's sweet spot (especially in winter), that'll tank your output. Happened on my narrowboat with dodgy crimps. Got a multimeter handy?

@MarshLover your post got cut off but I'm guessing you mean you're consistently below what you'd expect? Worth checking: are your battery voltage readings stable during charging? The Pylontechs can throttle the MPPT if they're seeing voltage drift or temperature issues. Also, what's your array orientation—any shading creeping in as seasons shift?

@MarshLover your post definitely got cut off! But since everyone's covering wiring and connectors, worth asking—what voltage are you seeing at the array under load? Also, are both Pylontechs actually communicating properly with the Victron? I had a similar issue in my van where one battery wasn't syncing, tanked the whole charge rate.

@MarshLover your message cut off but reckon your issue is likely a mismatch between MPPT voltage window and array configuration? SmartSolar 150/60 maxes at 150V input—if you've wired panels in parallel rather than series, you'll be stuck. What's your actual array voltage reading on the display?