Hello Everyone,

I have a weird one, my friend asked me to assist him with his Mecer SOL-I-AX-5VP 5Kw. He tells me flats were built near him and after the completion of the flats, the input voltage began to increase above 230v sometimes even higher 236v/240v. This would show an Error 51 High input voltage on the Mecer screen.

Using WatchPower v1.18 I changed the input Voltage to 240v and that was that.

Strangely, although the setting showed "Successful" and closing WatchPower and opening it again it has jumped back to 230v?? Been doing this for sometime now.

What I'm trying now is leaving his laptop connected the Inverter whilst it shows 240v on WatchPower and see what happens up until Friday.

Is there an issue perhaps with the Firmware or maybe the version of WatchPower I'm using? Or the Mecer itself has an issue with 240v setting? I don't know.

Anybody on the Forum experienced this as well?

Regards

Budgie

Are you changing to 240V with the "power" (really a "load") switch off? Otherwise, the command is ignored.

The other possibility is that the firmware isn't saving the voltage setting into EEPROM, so it's there for next time the inverter powers up from nothing. Perhaps change a setting like battery float voltage, then setting it back again? Then power the inverter down completely, power up and check that the 240 V setting has "stuck".

Hello Coulomb,

Long time no chat, thank you for replying.

Well, I did some research and this is what I discovered:

Error 51 on the Voltronic Axpert V platform is "Over current or surge" — it is not an AC input overvoltage protection. The inverter's AC input range is 90–280VAC (Appliances mode) or 170–280VAC (UPS mode, set in Program 03). At 236–238V, your utility voltage is well within spec and would not trip an overvoltage protection on its own.

The most likely mechanism:

If the inverter is in inverter mode (outputting from the battery, not in line/transfer mode) while the utility is present at 236–238V, there is a voltage differential between the inverter's 230V regulated output and the 236–238V grid.

This differential drives current back into the inverter from the grid side, which the inverter interprets as an overcurrent/surge event → Error 51.

The higher the grid voltage drifts above 230V, the more likely this becomes.

Other possible causes (from field reports on this model):

Cause Detail

Faulty current sensor or gate driver capacitors A degraded sensing circuit can falsely report overcurrent. Common on older Axpert V units.

Internal component failure Bulged capacitors (1000µF/16V, 470µF/25V) on the main board are a known failure mode that causes intermittent Error 51.

Thermal issue Overheating inside the enclosure can cause the protection to trip. Improving airflow sometimes resolves it.

PV interaction In some cases, PV input combined with high utility voltage triggers the fault even at moderate loads.

So, my understanding to assist my friend, that he take the Inverter to the agents, allow them to perform tests on the sensor or gate driver capacitors, inspect the Thermal for overheating.

Your thoughts Coulomb

Regards

Budgie

On 2026/09/01 at 3:35 PM, Kawaman said:

He tells me flats were built near him and after the completion of the flats, the input voltage began to increase above 230v sometimes even higher 236v/240v.

This indicates that the electrician in the new flats has made or altered a bad connection with the neutral. You are getting part of the phase to phase voltage. You must inform your electricity provider, ether Escom or the municipality.

22 hours ago, Beat said:

This indicates that the electrician in the new flats has made or altered a bad connection with the neutral. You are getting part of the phase to phase voltage.

It could also mean that the flats have solar panels installed, and the flats are exporting power to the grid. This often pushes up the grid voltage nearby.

On 2026/09/04 at 5:28 PM, Kawaman said:

Error 51 on the Voltronic Axpert V platform is "Over current or surge" — it is not an AC input overvoltage protection.

Yes, I was just looking that up.

When you say "Axpert V", for a moment I thought you meant Infini V models, which are very "Axpert like", except that they can export to the utility. But you also mentioned Watchpower, which is used for Axperts only (SolarPower is for monitoring Infinis). It might be better to refer to these models as "VP" models, or perhaps "SOL VP" models. The "VP" seem to to indicate PWM solar chargers, with 105V max PV input, and the panels pegged at battery voltage when bulk charging. "M" is the equivalent code for MPPT models (145 V max PV input, with Maximum Power Point Tracking). Apart from solar charging, the VP and M models are very similar.

On 2026/09/04 at 5:28 PM, Kawaman said:

The most likely mechanism:

If the inverter is in inverter mode (outputting from the battery, not in line/transfer mode) while the utility is present at 236–238V, there is a voltage differential between the inverter's 230V regulated output and the 236–238V grid.

This differential drives current back into the inverter from the grid side, which the inverter interprets as an overcurrent/surge event → Error 51.

Yes, I agree with this. In fact, I have a similar situation here, with two PIP-4048MS (roughly equivalent to a SOL-I-AX-5M). The mains voltage here is almost always over 240 V, so I've switched to an output voltage of 240 V as well. I did this (as far as I remember) merely to reduce the perceived thumping that the relays encountered when the mains and output voltages differ significantly. I've actually replaced my relays, but sadly haven't gotten around to a post mortem on the old ones to see how bad (if at all) the old ones were. I don't recall running into fault code 51, but it could be.

I just found a note in my phone about fault code 51. Eceman (who used to post on this forum regularly) says that a 2n2 capacitor across the MOSFETs fixes this fault code. It's not clear to me how this would help. He also says that an LM339 comparator on the control board has cured some 3 kVA models .

On 2026/09/04 at 5:28 PM, Kawaman said:

Internal component failure Bulged capacitors (1000µF/16V, 470µF/25V) on the main board are a known failure mode that causes intermittent Error 51.

I know that these cause restart cycles (where the power supply voltage collapses and the DSP resets or glitches), causing the LEDs to flash. I guess that with chaotic power supply voltages, all sorts of intermittent fault codes could be thrown up, including fault code 51.