Hi all! 

This is my first post on the forum. I've already learned so much about inverters / batteries / firmware etc. 

I have been experiencing an issue where whenever I connect the AC powercord to my inverter (even if the AC switch is off), my inverter faults and gives an error code 52. 

A simple restart using the DC battery circuit breaker sorts the issue out, until an AC power failure occurs etc. 

If there is no AC power connected, it seems to run perfectly fine on battery power. Also, seems to mess up the voltage meter after it trips on the inverter.

Has anyone experienced this before or know of any possible causes of this? Could it be incorrect wiring of the AC inputs? 

Thank you!

18 hours ago, Trick720 said:

This is my first post on the forum.

Welcome.

18 hours ago, Trick720 said:

whenever I connect the AC powercord to my inverter (even if the AC switch is off), my inverter faults and gives an error code 52. 

Do you not have this inverter wired in permanently? When this inverter is running full power and charging from utility, it could be drawing some 8 kW, which is way too much for your average "power cord". But perhaps it is wired in permanently, and you are referring to the AC input breaker.

Fault code 52 is "Bus voltage is too low", which is uncommon and sounds serious.

Do you have a proper 48 V battery connected, via thick (at least 35 mm²) battery cables? But if the battery was the problem, I'd expect fault code 04 (battery voltage low).

Hi Coulomb,

Thanks for the welcome! 

The inverter is not permanently wired to my house. I have an extension cable wired to the input socket and connected to an AC house output in case I need AC power. It is currently being used as a UPS and connected to my computer/wifi. Max load is around 250W at the moment so I don't think it is a load issue.

I have a 51.2v 100ah BSL LifePO4 battery connected - and there is sufficient voltage in the battery. (SOC is around 80%). 

The issue only happens when either the AC power is connected (for instance to a wall socket), or the AC electricity trips/reconnects. The inverter runs fine on battery power and solar power, and AC power when connected. 

Error 52 happens only when I connect the AC cord to the inverter. After a hard reset (i.e. switching the DC breaker off and on), the inverter runs fine again.

 

I've attached some watchpower setting screenshots to show the setup. It's currently cloudy, so not much PV production at the moment.

You may want to get an installer to come and check your grounding on the unit, it may be that, just thinking outside the box, I suspect your Inverter does not have an earth cable connected to the chassis that then runs to an earth rod outside... food for thought.

Hi Moffat,

Thank you for the information. Here is the watchpower error/fault log:

I switched off the AC power input at the wall socket at around 16:21:36 and fault 52 ended up showing on the inverter. However, in my understanding, Bus Soft start Fail is error 09? 

Again, a simple hard reset using the DC circuit breaker between the battery and the inverter allowed me to use the inverter. 

Edited January 8, 20223 yr by Trick720
Add additional information.

I ran additional tests as follows:

1) Unplugged the AC input - the battery voltage reported by the inverter ended up going far too high. 

2) Plugged the AC input back in, but kept it off (i.e. there was no input recorded) - again, the battery voltage reported by the inverter was inaccurately high.

3) Plugged the AC input back in, and turned it on. AC input was recording correctly and the battery voltage reported by the inverter was correct when comparing to the multimeter recording. 

Not sure if this makes any difference or provides better insight.

On 2022/01/09 at 1:08 AM, Trick720 said:

1) Unplugged the AC input - the battery voltage reported by the inverter ended up going far too high. 

That could be causing the firmware to go crazy, possibly resulting in fault code 52.

Is it possible that the battery voltage sense resistors could have gotten wet? That would cause the readings to go high.

I don't understand how restoring the AC-input could fix it though. I feel it has to be some sort of weird earth leakage somewhere.

Is it possible that the Solar Charge Controller, which has a separate CPU that also measures the battery, is coming on line at about the same time as the AC-input comes on, and that's confusing things? When the two battery measurements disagree, there is some sort of protocol for deciding who wins; I forget the details. The SCC does communicate its version of the battery voltage to the main inverter DSP (processor).

I purchased a grounding box - I suspect after doing research that it may have something to do with grounding. 
 

I will keep you updated if it helps once I get it.

Hey @Trick720 - Did you manage to get this sorted out ? - I have a similar scenario - I have 2 x 5kwh Lithiums connected to a 7.2KW Axpert Max, permanently wired to AC input - when power either fails or is restored - I end up with Error 52 - it is random - not every time. Powering off everything and on again and it all works fine again until the next time which could be 1 day or 2 days later.

Hi guys @Rosh - Quantum Solar @Coulomb @Trick720

Same issue here with Axpert max II 8kva.

Often during the night in SBU or SUB mode when batterie level is low the circuit breaker of the AC Input is kicked off. The default "line fail" is reporter on watch power app.

A little while after, when battery reaches the cut off voltage, the inverter stops and default "low battery" occurs, which is normal.

I also suspect the grounding but dont know how to solve it.

On 2024/02/17 at 11:12 PM, sylvain said:

the circuit breaker of the AC Input is kicked off.

Is this a pure breaker, or a combined Residual Current Breaker with Overload? If the latter, what is the trip current? Any RCBO before the inverter should have a high trip current, e.g. 300 mA, or at least 100 mA, because of the capacitors to earth inside high frequency switching devices like inverters.

On 2024/02/17 at 11:12 PM, sylvain said:

I also suspect the grounding but don't know how to solve it.

You need to ensure that there is only one connection from neutral to earth at any one location, given that the inverter will connect AC-out neutral to earth when it's not connecting AC-in to AC-out.

On 2024/09/24 at 10:51 AM, Scorp007 said:

If I read it correctly you will be using 2 x 24V lifepo4 in series to get 48V and then another 2 in series which you parallel with the 1st 2?

 

On 2024/02/17 at 9:12 AM, sylvain said:

Hi guys @Rosh - Quantum Solar @Coulomb @Trick720

Same issue here with Axpert max II 8kva.

Often during the night in SBU or SUB mode when batterie level is low the circuit breaker of the AC Input is kicked off. The default "line fail" is reporter on watch power app.

A little while after, when battery reaches the cut off voltage, the inverter stops and default "low battery" occurs, which is normal.

I also suspect the grounding but dont know how to solve it.

Hello i am having that exact issue did you ever solve yours at the time it was causing that thanks.