Problems with MUST inverters

[JBChiangRai]

An update on the PH18-5548+ inverters.

 

They are pieces of cr?p. They do sound like jet engines under load. Their ability to export power to the grid is very limited.

 

I have 3 in parallel mode, they won’t export more than about 1Kw to the grid even though more than 15Kw if solar power is available.

 

They won’t utilize much of the solar to power household appliances, preferring to switch into “Bypass” mode and use PEA power.

 

They will destroy Ant BMS if your battery backs have them by constantly switching between charge and discharge.

 

You will get zero support from Must in China and the suppliers here don’t fully understand them either.

 

I now have them operating in “Uti”lity mode as expensive whole house UPS’s and added 3 of Must PH5000-6Kw Grid-Tied inverters to output to PEA.  They have a design flaw, they should limit output when approaching max safe voltage output level instead they hit it, generate an error and restart where the process repeats.  You can however cadence them in the advanced settings so they don’t all fault at once.

[Tubulat]

6 hours ago, JBChiangRai said:

An update on the PH18-5548+ inverters.

 

They are pieces of cr?p. They do sound like jet engines under load. Their ability to export power to the grid is very limited.

 

I have 3 in parallel mode, they won’t export more than about 1Kw to the grid even though more than 15Kw if solar power is available.

 

They won’t utilize much of the solar to power household appliances, preferring to switch into “Bypass” mode and use PEA power.

 

They will destroy Ant BMS if your battery backs have them by constantly switching between charge and discharge.

 

You will get zero support from Must in China and the suppliers here don’t fully understand them either.

 

I now have them operating in “Uti”lity mode as expensive whole house UPS’s and added 3 of Must PH5000-6Kw Grid-Tied inverters to output to PEA.  They have a design flaw, they should limit output when approaching max safe voltage output level instead they hit it, generate an error and restart where the process repeats.  You can however cadence them in the advanced settings so they don’t all fault at once.

I don't connected them yet because I'm waiting for somebody who is willing to install the panels on the roof.

But your comment doesn't bode well.

Only your experience about support from Must, I agree.

From the distributor here in Thailand, where I bought the inverters and batteries, I've got a description about parallel connecting. Do you have this also?:  https://drive.google.com/file/d/1gA2CuHLru2f9VFihW1tlMd5ETrUtCZAD/view?usp=drivesdk

[BritManToo]

6 hours ago, JBChiangRai said:

I have 3 in parallel mode, they won’t export more than about 1Kw to the grid even though more than 15Kw if solar power is available.

My cheap Suoer GTis (2,500bht each) have generated 100 units to the grid this month 5x 330w panels).

There's something to be said for basic equipment that just does one job!

[Tubulat]

4 minutes ago, BritManToo said:

My cheap Suoer GTis (2,500bht each) have generated 100 units to the grid this month 5x 330w panels).

There's something to be said for basic equipment that just does one job!

I know, I know, you are a real lucky guy....there must be a different.

[sezze]

18 hours ago, JBChiangRai said:

An update on the PH18-5548+ inverters.

 

They are pieces of cr?p. They do sound like jet engines under load. Their ability to export power to the grid is very limited.

 

I have 3 in parallel mode, they won’t export more than about 1Kw to the grid even though more than 15Kw if solar power is available.

 

They won’t utilize much of the solar to power household appliances, preferring to switch into “Bypass” mode and use PEA power.

 

They will destroy Ant BMS if your battery backs have them by constantly switching between charge and discharge.

 

You will get zero support from Must in China and the suppliers here don’t fully understand them either.

 

I now have them operating in “Uti”lity mode as expensive whole house UPS’s and added 3 of Must PH5000-6Kw Grid-Tied inverters to output to PEA.  They have a design flaw, they should limit output when approaching max safe voltage output level instead they hit it, generate an error and restart where the process repeats.  You can however cadence them in the advanced settings so they don’t all fault at once.

There must be something wrong . I did just check and you say you got more then 15kW of solar , when checking here

https://www.mustups.com/wp-content/uploads/2016/07/PH1800-PLUS-折页.pdf  , i see that they accept 4kW . Even if it is full loaded on all 3 , then that still is only 12kW. Aren't you overdriving them , giving all kinds of faults ? Did you check all power going in and out , meaning amp/voltage meters on all in/outs to check that you are well in the limits of all ? You did put them in parallel mode to combine the output , try to dismantle the parallel com , and see if it works then , just to check if there might be something wrong with the parallel mode ... . I do know it is a hassle , but since it isn't working as it should ( the noise will be there ..) , then we should find a reason why it isn't . 

[JBChiangRai]

The 3 Must PH18-5548+ units are connected correctly in parallel mode and yes They we’re supplied with the same documentation on the google drive mentioned but in paper form.

 

It appears to me that they are primarily designed for cycling the batteries. I have two 14 KwHr battery packs in parallel give ng me 28 KwHr in LiFePo4 batteries on mine. 
 

My batteries came fully charged because a friend built them for me and they worked great on his system.

 

On my installation, the Ant BMS units failed, the first one failed within a few hours and the second one within a day.

 

When charged, one inverter would be in charge mode, another in discharge mode, one would disconnect the solar panels entirely and switch into bypass mode.

 

They take turns at exporting power to PEA or powering the load and take turns at screaming like jet engines.

 

I did have more than 4Kw of panels on each it I don’t think that is the problem as the problems I was having were at all times of the day when the solar irradiance was well under 4Kw per inverter.

 

It’s possible that once my Ant BMS systems were goosed it was no longer possible for them to perform properly as the batteries still had output but wouldn’t accept a charge.

 

However, even before this, I was expecting to see lots of solar power with limited or no PEA supply and we found that as soon as the load was up to 2 or 3 Kw they were producing very little solar power and drawing most of the load from PEA.  
 

I had mine configured differently from most, I only wanted my batteries using in the event of a power cut and I suspect this is what they don’t like.

 

They are now working flawlessly as UPS units with no solar connected.

 

I have 3 of Must PH5000-6Kw units in parallel Grid-Tied exporting to PEA, we have hit over 80 KwHrs exported in one day, but the grid is weak here being several hundred meters from the transformer and these inverters don’t perform as I would want.

 

I would prefer them to attempt to export their full power but if in doing so they are going to exceed the maximum safe voltage set on the advanced parameter screen then I would like to see them throttle back their output instead of crossing that threshold, erroring, disconnecting, entering delay before restart then the whole process repeats.

 

They are provided with a Hall sensor coil to power match with your load, it seems crazy to me that the power limitation feature can’t be used to stop it crossing a safe output voltage.

 

I have cadenced my 3 inverters, so the first one fails and the next one only fails 2 volts above the first but what I want them to do is climb to 253v and stay there, pumping out more power if the grid will accept it.

 

There are some parameters on the advanced screen I don’t understand and all Must will tell me is “Don’t touch them”, parameters like 
 

Power Return Gradient %

Statism s %

Power Limitation Delay time (s)

 

perhaps they are only related to the Hall sensor (they are all set to zero), but I’m not happy having parameters I can adjust with no explanation available.

[Crossy]

@JBChiangRai I know you've "sorted" the issue, but did you try running in one of the more conventional hybrid modes, charge during the day, discharge at night? (maybe with no mains connection available for it to switch to)

 

It's not unusual for the lesser used modes to have software "features" (bugs), we are still finding them on (not solar) systems that have been in service for several years. Turn on a feature, find it doesn't work, then find the DLP (Defect Liability Period) expired last month ????

 

[JBChiangRai]

Actually I didn’t try them in a more conventional mode.

 

I think my expectations were probably unreasonable, I wanted to export as much as possible to the grid during the day, drawing it back at night and keeping the expensive batteries for power cuts.

 

I think the grid export feature on the PH18 hybrid inverters is an afterthought and they’re not meant to export very much.

 

I should have listened to the supplier on Lazada, he warned me off them saying they were too complicated.

[Peterphuket]

Don't know if this forum still being consulted but I have problems to connect my Wi-Fi plug14 to the MUST inverter, is there anybody with experience with this?

[Peterphuket]

On 6/23/2021 at 6:21 AM, JBChiangRai said:

The 3 Must PH18-5548+ units are connected correctly in parallel mode and yes They we’re supplied with the same documentation on the google drive mentioned but in paper form.

 

It appears to me that they are primarily designed for cycling the batteries. I have two 14 KwHr battery packs in parallel give ng me 28 KwHr in LiFePo4 batteries on mine. 
 

My batteries came fully charged because a friend built them for me and they worked great on his system.

 

On my installation, the Ant BMS units failed, the first one failed within a few hours and the second one within a day.

 

When charged, one inverter would be in charge mode, another in discharge mode, one would disconnect the solar panels entirely and switch into bypass mode.

 

They take turns at exporting power to PEA or powering the load and take turns at screaming like jet engines.

 

I did have more than 4Kw of panels on each it I don’t think that is the problem as the problems I was having were at all times of the day when the solar irradiance was well under 4Kw per inverter.

 

It’s possible that once my Ant BMS systems were goosed it was no longer possible for them to perform properly as the batteries still had output but wouldn’t accept a charge.

 

However, even before this, I was expecting to see lots of solar power with limited or no PEA supply and we found that as soon as the load was up to 2 or 3 Kw they were producing very little solar power and drawing most of the load from PEA.  
 

I had mine configured differently from most, I only wanted my batteries using in the event of a power cut and I suspect this is what they don’t like.

 

They are now working flawlessly as UPS units with no solar connected.

 

I have 3 of Must PH5000-6Kw units in parallel Grid-Tied exporting to PEA, we have hit over 80 KwHrs exported in one day, but the grid is weak here being several hundred meters from the transformer and these inverters don’t perform as I would want.

 

I would prefer them to attempt to export their full power but if in doing so they are going to exceed the maximum safe voltage set on the advanced parameter screen then I would like to see them throttle back their output instead of crossing that threshold, erroring, disconnecting, entering delay before restart then the whole process repeats.

 

They are provided with a Hall sensor coil to power match with your load, it seems crazy to me that the power limitation feature can’t be used to stop it crossing a safe output voltage.

 

I have cadenced my 3 inverters, so the first one fails and the next one only fails 2 volts above the first but what I want them to do is climb to 253v and stay there, pumping out more power if the grid will accept it.

 

There are some parameters on the advanced screen I don’t understand and all Must will tell me is “Don’t touch them”, parameters like 
 

Power Return Gradient %

Statism s %

Power Limitation Delay time (s)

 

perhaps they are only related to the Hall sensor (they are all set to zero), but I’m not happy having parameters I can adjust with no explanation available.

Can I ask you, do you have the Wi-Fi plug14 connected to your MUST inverter?

[JBChiangRai]

On 7/20/2021 at 5:30 PM, Peterphuket said:

Can I ask you, do you have the Wi-Fi plug14 connected to your MUST inverter?

No but I still have some WiFi RTU for them, I’ve never connected them

[Peterphuket]

2 minutes ago, JBChiangRai said:

No but I still have some WiFi RTU for them, I’ve never connected them

OK, thanks I have 2 of them but don't get connected.

 

Another question, I have lithium batterys connected, but because there is no sun the last days the batterys drawns empty so when i take a look in the morning i get an warning signal and code 04, meaning battery empty, only when i disconnect the batterys and switch on again, the warning signal stops and then the inverter switched to the grid to load the batterys. Do you have the same experience?

[Peterphuket]

On 6/23/2021 at 4:55 AM, sezze said:

There must be something wrong . I did just check and you say you got more then 15kW of solar , when checking here

https://www.mustups.com/wp-content/uploads/2016/07/PH1800-PLUS-折页.pdf  , i see that they accept 4kW . Even if it is full loaded on all 3 , then that still is only 12kW. Aren't you overdriving them , giving all kinds of faults ? Did you check all power going in and out , meaning amp/voltage meters on all in/outs to check that you are well in the limits of all ? You did put them in parallel mode to combine the output , try to dismantle the parallel com , and see if it works then , just to check if there might be something wrong with the parallel mode ... . I do know it is a hassle , but since it isn't working as it should ( the noise will be there ..) , then we should find a reason why it isn't . 

May I ask you, do you have the same inverters?

[sezze]

34 minutes ago, Peterphuket said:

May I ask you, do you have the same inverters?

No i dont have them

[JBChiangRai]

4 hours ago, Peterphuket said:

OK, thanks I have 2 of them but don't get connected.

 

Another question, I have lithium batterys connected, but because there is no sun the last days the batterys drawns empty so when i take a look in the morning i get an warning signal and code 04, meaning battery empty, only when i disconnect the batterys and switch on again, the warning signal stops and then the inverter switched to the grid to load the batterys. Do you have the same experience?

I’m guessing you have LiFePo4 batteries?

 

You shouldn’t use the Lithium setting on the inverters, that is for Lithium Ion, use the “Use” User Defined setting and program the bulk and float voltages and charge currrents according to how you want (ie max SoC) also set the inverters to restart on error.  
 

I now only use them for backup with no PV attached, basically as whole house UPS charging each pack with 45 Amps from PEA only and a max SoC of about 85%.  I also have 3 of MUST PH5000 series 6Kw inverters that I use grid-tied, producing an average of 80KWhrs per day, best day so far was over 120KWhrs.

[Peterphuket]

13 hours ago, JBChiangRai said:

I’m guessing you have LiFePo4 batteries?

 

You shouldn’t use the Lithium setting on the inverters, that is for Lithium Ion, use the “Use” User Defined setting and program the bulk and float voltages and charge currrents according to how you want (ie max SoC) also set the inverters to restart on error.  
 

I now only use them for backup with no PV attached, basically as whole house UPS charging each pack with 45 Amps from PEA only and a max SoC of about 85%.  I also have 3 of MUST PH5000 series 6Kw inverters that I use grid-tied, producing an average of 80KWhrs per day, best day so far was over 120KWhrs.

NO, I use this batteries "BYD battery 48V 260Ah assembled with 1xANT smart BMS 320A plus 1x16S 5A active balancer"

2 sets, and bought this by the same shop as the inverters: Thai Jean Trade, and he give the info how to adjust the inverters for this batterie packs.

[Peterphuket]

1 hour ago, Peterphuket said:

NO, I use this batteries "BYD battery 48V 260Ah assembled with 1xANT smart BMS 320A plus 1x16S 5A active balancer"

2 sets, and bought this by the same shop as the inverters: Thai Jean Trade, and he give the info how to adjust the inverters for this batterie packs.

OK, special for Crossy

[FarangRimPing]

On 7/20/2021 at 5:28 PM, Peterphuket said:

Don't know if this forum still being consulted but I have problems to connect my Wi-Fi plug14 to the MUST inverter, is there anybody with experience with this?

My Wi-Fi Plug14 worked well for over a year, but it stopped working about a week ago. I tried resetting it and it doesn't even send out any wi-fi signal, so it's kaput. I contacted the MUST Thailand distributer in Rayong, who I bought all of my solar equipment from, and asked to purchase a replacement. He ignored my emails. I then contacted him through Lazada chat and he replied after a day. His reply was a brief "I can't help you". I've now filled out the quote form on the China MUST site but no response as of yet. I wonder if I can use a different company's wi-fi data logger but I'm guessing that the firmware is vendor specific.

[Peterphuket]

40 minutes ago, FarangRimPing said:

My Wi-Fi Plug14 worked well for over a year, but it stopped working about a week ago. I tried resetting it and it doesn't even send out any wi-fi signal, so it's kaput. I contacted the MUST Thailand distributer in Rayong, who I bought all of my solar equipment from, and asked to purchase a replacement. He ignored my emails. I then contacted him through Lazada chat and he replied after a day. His reply was a brief "I can't help you". I've now filled out the quote form on the China MUST site but no response as of yet. I wonder if I can use a different company's wi-fi data logger but I'm guessing that the firmware is vendor specific.

If you like, you can get one from me, I have 2 pieces as I say I don't get working it but when you have one from me, maybe you can get working it and can explain me.

[Crossy]

47 minutes ago, FarangRimPing said:

I wonder if I can use a different company's wi-fi data logger but I'm guessing that the firmware is vendor specific.

 

It's even market specific. I have two Sofar inverters, one from the Thai market, one from the ML China market. They have different WiFi units that talk to different servers and they won't talk to the other WiFi unit if you swap them.

 

I've given up with the WiFi and gone MODBUS and NodeRed.

 

[sezze]

Something i have found on another website about Sorotec Revo inverters ( they are sold in Thailand also ) . They also make some noise , but somebody added changing his original fans by 12cm Be Quiet computer fans with a duct entrance , making his unit whisper quiet , and using less power then the original fans . Noctua and Be Quiet fans are available in Thailand for around 600-900 baht a piece . Since warranty is not really happening in Thailand it might be a very good solution to a known problem of most if not all ventilator inverters ( like the Must units ) .