Problem diagnosis · Victron Energy

Victron MPPT Error Codes — PV Overvoltage, String Sizing & SmartSolar Diagnosis

Your Victron SmartSolar or BlueSolar MPPT controller is showing an error code — most likely Error 33 (PV overvoltage) or Error 38 (PV input shutdown). The solar charge controller has stopped generating and the battery is no longer charging from solar. This is almost always a string configuration issue, and it gets worse in cold weather.

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Error 33 & 38 specialists
SmartSolar 150 & 250 series
Cold-weather Voc calculations

MPPT error stopping your solar charging?

We review VRM solar data, calculate your string Voc with cold-weather correction, and determine whether the fix is a reconfiguration or a controller replacement.

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13 Trustpilot reviews

Trustpilot Google

I have a GivEnergy system consisting of two batteries, two inverters and a controlling EMS (Energy Management System) which has not worked since Nov 2025. After six months I discovered Solar Tech Support, reached out to them and Ron phoned me back – how often do you get that service? Could not be more helpful – worked directly with me over the phone, outside what I would call normal working hours. Lucid explanations and we were able to discuss the issues and history using camera and email history. As this was a very rare setup, Ron was able to access an EMS expert in the field to confirm the solution. One sunny day in, I am now only paying for standing charge and a few pence for spikes in grid consumption while battery catches up with house demand.

Ian · May 2026 Trustpilot

When my GivEnergy system had an issue, I was completely left without support and had honestly lost all hope. Thankfully, I searched online and found Ron, which completely turned things around. After sending him a message, he responded incredibly fast and called me to assure me that he would get the problem fixed. I really admire his dedicated, supportive nature and his determination to find a solution. With this kind of outstanding attitude and customer service, he has absolutely secured a future customer in me.

Sree · May 2026 Trustpilot

Ron want out of is way to help, nothing was to much. He was very thorough in what he did Very knowledgeable I would highly recommend Ron and his company He did a fantastic job for me. if you have any problems, he'll do his best to help you out and resolve your problem. I wouldn't hesitate to recommend them

Dennis Brown · May 2026 Trustpilot

Ron took me through a diagnostic to confirm my GivEnergy Inverter had a fault. A common one as it turns out with the AC Inverter. As GivEnergy is defunct there is no immediate fix, aside from sourcing 2nd hand replacement. It may be that a fix becomes available over the summer which would make a lot of GivEnergy customers happy (Again)

Tony Deacon · May 2026 Trustpilot

Contacted Ron with a problem and he sorted it out quickly with no problems at all. Very knowledgeable on anything solar/ batteries. I would recommend him to anyone

Phill · May 2026 Trustpilot

I've spoken to Ron a couple of times with issues with my Givenergy installation. Such a friendly knowledge guy very highly recommended. Thank you very much for resolving my issues

michael fairhurst · May 2026 Trustpilot

Contacted Solar Tech Support in desperation. After explaining the issues I had with my system a diagnosis was made and a solution proposed. Fantastic service, even contacted a manufacturer to arrange replacement parts for me. Great communications, explained all they were doing and what I had to do, clearly and precisly. Followed up to confirm all was ok. Excellent service.

Mr Machin · May 2026 Trustpilot

After GivEnergy went into liquidation, just my luck, my battery started playing up (internal board crashed). Contacted my installer - not interested! Found Solar tech support on a Google search. Sooo glad I found this company! Ron is extremely helpful and has plenty of experience. He soon confirmed what the fault was, and helped me to get my system up and running again. Now moved my GivEnergy account to Solar tech support, and will definitely use again if I have more issues. Unusual to find such a helpful company in these times, no morons reading scripts, just direct contact with the engineer.

Keith Ballard · Apr 2026 Trustpilot

Contacted Solar Tech Support when trying to understand what my Givenergy inverter problem might be and what might be my options. Received good/honest advise which backed up my thoughts.

Hugh Speirs · Apr 2026 Trustpilot

Ron is a super star. Two months ago my GivEnergy battery failed a firmware upgrade leaving it a brick. My installer couldn't/wouldn't fix it. GivEnergy couldn't/wouldn't fix it. Then they went into administration and all hope was lost. A flurry of emails later and Ron had diagnosed the fault (failed USB flash drive, something I'd suspected) and talked me through resolving it. Two months of nothing resolved in about 3 hours. It's great to work with someone who pays attention to the details, knows that they're doing (not just following a script) and gets stuff sorted without a fuss or up-charging.

Christopher · Apr 2026 Trustpilot

I can add to the list of customers who had already 'given up' on GivEnergy due to their appalling customer service, and that was before they went into administration (their Trustpilot reviews don't lie!). So you can imagine my desperation when, having changed my ISP and my Inverter, predictably, proving to be the only device that didn't connect automatically to my new network, I found zero prospect of any customer support with GivEnergy having called in the administrators just five days earlier! The salvation came from Solar Tech Support. My IT advisor stumbled across their web site and some very helpful tips for beleaguered GivEnergy customers, as well as an offer to provide direct assistance. Nothing ventured, I decided to drop them an E-Mail, with very low expectations based on my experience of GivEnergy customer support. Within an hour Ron had responded with some pin point advice, and after a few exchanges of E-Mails he had nailed the problem, enabling the combined efforts of my IT advisor and solar installer to resolve it and reconnect my Inverter. Thank you Solar Tech Support, and Ron in particular, for coming to the aid of a deserted and despondent GivEnergy customer. Expert, razor sharp advice and first class customer service, even though I wasn't officially a customer.

customer · Apr 2026 Trustpilot

This company are a rare gem, I had a very unusual problem following a failed firmware upgrade on my GivEnergy kit. I then found out GivEnergy were in administration and had dismissed all their support staff! None of the usual fixes to try and restore my inverter comms would work, and I looked everywhere, forums, GivEnergy youtube support videos - even AI couldn't figure it out. My installer was talking about huge sums for system replacements, and being vague / evasive about if they'd even install replacement GivEnergy inverter. Enter Solar Tech Support, reassuring and knowledgeable from the very start, I've learnt loads about my solar system though the friendly chat while my engineer worked as he diagnosed the problem and figured out a fix procedure that I've not found anywhere else - amazing . If you need solar system repairs - especially if you like me have been left high and dry by GivEnergy, I cannot recommend this company enough. Give them a call.

Andy Thomas · Apr 2026 Trustpilot

I sent a message on their website regarding a problem I have on my Givenergy system. Although not supplied by Ronald, I thought it was worth an email. Within the hour on a Saturday, he phoned and we discussed the problem. He logged in remotely and gave excellent advice. I'm too far away for his on-site help but he did diagnose the problem and was happy also to chat through my thoughts about an upcoming solar/battery install I'm planning. Great bloke.... if only he was nearer!

Philip · Apr 2026 Trustpilot

Ian · May 2026 Trustpilot

Sree · May 2026 Trustpilot

Dennis Brown · May 2026 Trustpilot

Tony Deacon · May 2026 Trustpilot

Contacted Ron with a problem and he sorted it out quickly with no problems at all. Very knowledgeable on anything solar/ batteries. I would recommend him to anyone

Phill · May 2026 Trustpilot

I've spoken to Ron a couple of times with issues with my Givenergy installation. Such a friendly knowledge guy very highly recommended. Thank you very much for resolving my issues

michael fairhurst · May 2026 Trustpilot

Mr Machin · May 2026 Trustpilot

Keith Ballard · Apr 2026 Trustpilot

Contacted Solar Tech Support when trying to understand what my Givenergy inverter problem might be and what might be my options. Received good/honest advise which backed up my thoughts.

Hugh Speirs · Apr 2026 Trustpilot

Christopher · Apr 2026 Trustpilot

customer · Apr 2026 Trustpilot

Andy Thomas · Apr 2026 Trustpilot

Philip · Apr 2026 Trustpilot

MPPT error codes MultiPlus not charging VE.Bus error codes Battery BMS disconnect VictronConnect setup System underperforming Victron hub →

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Safety note: PV strings can produce dangerous voltages — up to 250V DC or higher depending on configuration. Do not disconnect MC4 connectors under load or in direct sunlight. If you need to isolate the PV string, use the DC isolator switch. Never work on PV wiring without confirming zero voltage with a multimeter.

Diagnostics

5-step MPPT error code diagnosis

MPPT errors 33 and 38 are overwhelmingly caused by PV string voltage exceeding the controller's maximum input. Cold weather makes panel voltage rise — a string that works in summer can trip the controller on a cold morning. Start with the error code, then verify the maths.

Identify the specific MPPT error code from VictronConnect or VRM

Open VictronConnect (Bluetooth) or the MPPT device page in VRM. The error code is shown on the main status screen:

Common MPPT error codes

Error 2 — Battery voltage too high: Battery overvoltage detected — check charge parameters and BMS communication

Error 17 — Controller overtemperature: MPPT too hot — check ventilation, mounting location, ambient temperature

Error 18 — Controller overcurrent: PV current exceeds rated input — check string configuration

Error 33 — PV overvoltage: PV input voltage exceeded maximum Voc rating — most common error

Error 38 — PV input shutdown: Protective shutdown following sustained overvoltage — may indicate internal damage

Check the error history in VictronConnect under the History tab. If Error 33 only appears on cold mornings and clears by midday, this confirms a cold-weather Voc issue.

Calculate your PV string open-circuit voltage including cold-weather correction

The key calculation: panels in series × panel Voc × cold correction factor

Example calculation

Panel: 400W, Voc = 46.2V (from datasheet at STC / 25°C)

String: 4 panels in series → 4 × 46.2V = 184.8V at STC

Cold correction (−10°C): +12% → 184.8V × 1.12 = 207.0V

SmartSolar 150/45 max: 150V → exceeds by 57V — Error 33 guaranteed

SmartSolar 250/100 max: 250V → within limits ✓

The temperature coefficient for Voc is on the panel datasheet — typically −0.25% to −0.35% per degree Celsius. For a rough UK calculation, add 10–15% to the STC Voc to cover worst-case winter conditions (−10°C ambient, panel at sub-zero before sunrise).

Use the Victron MPPT Calculator at victronenergy.com to verify your configuration. The calculator includes location-based temperature data.

Check whether the string configuration exceeds the controller rating

Common UK configurations that trigger Error 33:

• SmartSolar 150/45: 4× high-power panels (400W+) in series — Voc typically 184V+ at STC, 206V+ cold-corrected. Must be reconfigured to 2s2p or 3s1p.

• SmartSolar 150/35: Even 3× panels with Voc above 50V can exceed 150V cold-corrected. Check panel specs carefully.

• SmartSolar 250/100: 6× panels in series with Voc above 42V can exceed 250V in cold weather. Less common but possible with newer high-efficiency panels.

• Mixed panels: If panels of different models are wired in series, use the highest individual Voc for your calculation — mismatch can cause unexpected voltage distribution.

The fix for an oversized string is to reconfigure: reduce panels in series (add parallel strings if needed), or upgrade to a higher-voltage MPPT controller.

Inspect PV wiring for damage or partial shading issues

If the string Voc calculation is within the controller rating but errors persist, investigate the wiring:

• MC4 connectors: Check for moisture ingress, corrosion, loose connections, or cracked housings. Damaged MC4s can cause voltage spikes.

• Cable insulation: Inspect for physical damage along cable runs — rodent damage in lofts, UV degradation on exposed runs, pinch points at roof penetrations.

• Junction boxes: Open and inspect panel junction boxes for water ingress or burnt diodes. A failed bypass diode can change the string's voltage behaviour.

• Ground fault: An insulation breakdown between the DC circuit and earth can cause voltage anomalies. Measure string voltage to earth with a multimeter.

Measure the actual string Voc at the MPPT input terminals using a multimeter. Compare with your calculated value — a significant discrepancy indicates a wiring fault.

Assess whether the MPPT controller needs replacement or reconfiguration

Two outcomes are possible at this point:

String exceeds rating → Reconfigure

Reduce panels in series, add parallel strings, or upgrade to a higher-voltage controller. This is the most common resolution and does not require replacing the MPPT itself.

String within spec → Controller may be damaged

If the string is correctly sized but overvoltage errors persist, the controller's input protection (varistors, TVS diodes) may have degraded from a previous overvoltage event or lightning surge. The MPPT likely needs replacing.

A remote diagnostic can confirm the fault pattern from VRM historical data — we check daily peak PV voltage, error frequency, and whether the issue correlates with temperature before recommending a replacement.

If replacing, ensure the new controller's Voc rating exceeds your cold-corrected string voltage by at least 10% margin. See our VictronConnect setup guide for configuring a new controller.

Why cold weather is the hidden cause of most MPPT errors

Solar panels are rated at Standard Test Conditions (STC) — 25°C cell temperature, 1000W/m² irradiance. In the UK, panel temperatures regularly drop to −5°C or below in winter, especially in Scotland, Wales, and northern England. At these temperatures, the open-circuit voltage of a solar panel rises significantly — typically 10–15% above the STC value. A string that is safely within the MPPT controller's limit at 25°C can exceed it at −10°C. This is why Error 33 is seasonal — it appears in November or December and disappears in spring, leading homeowners to think it has "fixed itself." It hasn't. The underlying misconfiguration is still there, and it will return every winter.

The SmartSolar 150/45 is the most commonly affected controller in the UK because it hits its 150V limit quickly with modern high-efficiency panels. Three 400W+ panels in series produce around 138V at STC — apparently fine — but 155V cold-corrected, which exceeds the limit. Installers who size strings at STC without applying the temperature correction are the root cause of most Error 33 cases we diagnose. The SmartSolar 250/100 gives much more headroom and is now recommended as the standard choice for UK off-grid and hybrid installations.

MPPT error codes — common questions

What does Victron MPPT Error 33 mean?

Error 33 means PV input voltage has exceeded the controller's maximum rating. This is an overvoltage protection trip — the controller shuts down the PV input to protect itself. The most common cause is too many panels in series for the controller's voltage rating, especially in cold weather when panel Voc rises 10–15% above the datasheet STC value.

Why does my Victron MPPT trip in cold weather but not in summer?

Solar panel Voc increases as temperature drops. At −10°C, Voc can be 10–15% higher than at the 25°C STC rating. A string that's within limits in summer can exceed the controller's maximum on a cold winter morning. This is why MPPT manufacturers require cold-weather Voc correction when sizing strings — and why Error 33 is seasonal in the UK.

How do I fix Victron MPPT Error 38?

Error 38 is a PV input shutdown — the controller has disabled solar input as a protective measure. Resolve the underlying overvoltage by reconfiguring the string, then clear the error by disconnecting PV and battery, waiting 30 seconds, and reconnecting battery first then PV. If Error 38 persists after reconfiguration, the controller's input protection circuit may be damaged from a previous overvoltage event.

Can I add more panels to my Victron SmartSolar without upgrading?

You can add panels in parallel without increasing string voltage — the controller clips excess current above its rated output. But you cannot add panels in series if doing so pushes the cold-corrected Voc above the controller maximum. If you need more series voltage for long cable runs, upgrade to a higher-voltage model (e.g. 150-series to 250-series SmartSolar).

How much does it cost to diagnose an MPPT controller fault?

Our free remote diagnostic and covers VRM performance data, MPPT error history, PV string voltage calculation with cold-weather correction, and controller health assessment. If the MPPT needs replacing, we confirm the correct model and verify the new configuration before ordering.

Book

MPPT error killing your solar generation?

Tell us the MPPT model (e.g. SmartSolar 150/45), the error code, your panel specs, and how many panels are in each string. We'll calculate whether a reconfiguration or controller replacement is needed.

Free remote diagnostic · no fix, no fee
Cold-weather Voc calculations
String reconfiguration guidance

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