on my MUST hybrid inverter;
If my battery runs out and results in a fault "battery voltage is too low", my expectation would be that after the sun comes and starts charging again via solar, the inverter should be able to switch itself on again.
This is not happening and I am not able to configure this desired behavior via the settings.
any ideas?

3 hours ago, Kz_ said:

on my MUST hybrid inverter;
If my battery runs out and results in a fault "battery voltage is too low", my expectation would be that after the sun comes and starts charging again via solar, the inverter should be able to switch itself on again.
This is not happening and I am not able to configure this desired behavior via the settings.
any ideas?

It's possible that the BMS shuts the battery down so no power can get from solar to charge it. It will have to be jump started if it does not come on with a reset. This if it's a lithium. 

Provide more details of the make and model of the battery in use. 

Edited November 21, 20232 yr by Scorp007

20 minutes ago, Scorp007 said:

It's possible that the BMS shuts the battery down so no power can get from solar to charge it. It will have to be jump started if it does not come on with a reset. This if it's a lithium. 

Provide more details of the make and model of the battery in use. 

Yes, it is a LiFePO4.
The BMS doesn't shutdown. I've avoided that by making sure the cutoff voltage is well above the BMS shutdown voltage.
The shutdown is on the MUST inverter after it records a 'fault', normally when this happens, I have to manually disconnect the inverter from the battery for the inverter itself to restart inverting, which I'd like to avoid

Thanks.

2 hours ago, Kz_ said:

Yes, it is a LiFePO4.
The BMS doesn't shutdown. I've avoided that by making sure the cutoff voltage is well above the BMS shutdown voltage.
The shutdown is on the MUST inverter after it records a 'fault', normally when this happens, I have to manually disconnect the inverter from the battery for the inverter itself to restart inverting, which I'd like to avoid

Thanks.

Quite a schlep to disconnect the inverter to battery. Do you have a fuse disconnect or circuit breaker between the 2 to make it an easy task?

2nd place. Can you just switch off the battery and on again if it might get the inverter to start?

17 minutes ago, Scorp007 said:

Quite a schlep to disconnect the inverter to battery. Do you have a fuse disconnect or circuit breaker between the 2 to make it an easy task?

2nd place. Can you just switch off the battery and on again if it might get the inverter to start?

Yes, I guess I could add a circuit breaker.

Though I was hoping for a way to wake up the device automatically when the sun is up 

23 minutes ago, Kz_ said:

Yes, I guess I could add a circuit breaker.

Though I was hoping for a way to wake up the device automatically when the sun is up 

Funny how the Must works. Although not when the inverter switched off with low voltage my Axpert wakes up to start charging even with the on/off in the off position every morning at 1st good light. 

Have you perhaps tried it by leaving it off. 

2 minutes ago, Scorp007 said:

Funny how the Must works. Although not when the inverter switched off with low voltage my Axpert wakes up to start charging even with the on/off in the off position every morning at 1st good light. 

Have you perhaps tried it by leaving it off. 

To clarify it does work up to charge but does not invert power to the AC side. 

So, I'll find it charging but not supplying power

any ideas here? this still bothers me.

additional observations:
The inverter will shut down at the low DC voltage mark. which is expected.
The inverter will attempt to restart at the first sign of daylight. But this light is not enough to sustain the system so it will shut down soon after, after a few minutes.
at this point, the inverter will continue charging the batteries but not inverting. This situation persists until I attempt to manually clear the fault code. switching off for a few minutes.
 

8 hours ago, Kz_ said:

any ideas here? this still bothers me.

additional observations:
The inverter will shut down at the low DC voltage mark. which is expected.
The inverter will attempt to restart at the first sign of daylight. But this light is not enough to sustain the system so it will shut down soon after, after a few minutes.
at this point, the inverter will continue charging the batteries but not inverting. This situation persists until I attempt to manually clear the fault code. switching off for a few minutes.
 

The inverter will normally  stay on grid up to the battery voltage as set. Setting 13 I think on the Axpert. It takes a while. 

Once it cuts out it is normally better to charge from grid and in bypass than from weak PV in the morning. Provided you have grid. 

Edited April 26, 20242 yr by Scorp007

What modes are you running (output and charger source) ?

What do you have for parameters 20 and 21 (similar to Axpert 12 and 13 settings)?

I have a MUST too, but haven't tried to run it down fully. I did set my BMS cutoff lower than the inverter cutoff.

Anyways, I suspect that it will charge up the battery up to either setting 20 or 21 (depending on other settings, like LBU/BLU), and only then it will enable AC output from inverter. But I would also expect AC out to be in bypass mode during this charging, if grid is available.

 

But you got me thinking that I really need to check these edge cases with my setup, to make sure it can recover in case of a prolonged power outage and cloudy weather.

 

8 hours ago, Kz_ said:

 This situation persists until I attempt to manually clear the fault code. switching off for a few minutes.
 

If it has got grid and no AC output no matter the state of the battery then there is a problem. 

On the similar Axpert a low voltage error 4 (or cut out low IIRC) will stay on the screen so that one can see the condition did exist even if charging has taken place until one switches the unit off and on again then it is cleared. Actually great to know the condition did exist. 

1 hour ago, Scorp007 said:

If it has got grid and no AC output no matter the state of the battery then there is a problem. 

On the similar Axpert a low voltage error 4 (or cut out low IIRC) will stay on the screen so that one can see the condition did exist even if charging has taken place until one switches the unit off and on again then it is cleared. Actually great to know the condition did exist. 

the situation appears when the grid is not available.
If a similar situation appears when the grid is available, this problem doesn't arise, as you said, it will flash on the screen but work as usual

4 hours ago, meetyg said:

What modes are you running (output and charger source) ?

What do you have for parameters 20 and 21 (similar to Axpert 12 and 13 settings)?

I have a MUST too, but haven't tried to run it down fully. I did set my BMS cutoff lower than the inverter cutoff.

Anyways, I suspect that it will charge up the battery up to either setting 20 or 21 (depending on other settings, like LBU/BLU), and only then it will enable AC output from inverter. But I would also expect AC out to be in bypass mode during this charging, if grid is available.

 

But you got me thinking that I really need to check these edge cases with my setup, to make sure it can recover in case of a prolonged power outage and cloudy weather.

 

01.  Output source priority selection  -- SBU

05. solar supply priority – LBU

06. overload bypass – bye, bypass enabled

07. autorestart when overload occurs – enabled

08. autorestart when overtemperature occurs – enabled

10. charger source priority – CSO

11. maximum charging current – 60A

13. maximum utility charging current – 10A

14. battery type – USE

17. bulk charging current (CV voltage) – 14.0V

18. floating charging voltage – 13.6V

19. low DC cut off voltage – 12.0V

20. battery stop discharging when grid is available  –- 12.1V

21. battery stop charging when grid is available  -- 12.5V

27. Record Fault code – FON
28. Solar power balance – SBD

29. power saving mode – SEN

OK, so it seems like the settings are OK. At least I would expect the inverter to supply output when battery reaches 12.5v.

How long did you wait to see if output is re-applied ? Are you sure battery is charging (is voltage rising slowly)?

BTW, you have power saving mode ENABLED. Have you tried to put a large enough load (say above 50w) ?

With this mode enabled, the inverter will scan every few seconds (could be up to 30) to see if a load is applied, and only then it starts supplying power. But it needs to see a large enough load in order to activate output.

I would suggest disabling this mode first, and then retest that low battery fault your are experiencing.

Edited April 27, 20242 yr by meetyg

On 2024/04/26 at 8:48 PM, Kz_ said:

28. Solar power balance – SBD

Just another tip: I would suggest you change this to ENABLE.

According to the manual (and my own observations), it enables the inverter to pull maximum PV in order to charge the battery, but also to power any loads.

If it's disabled, you allow it to take a maximum of setting #11 (60 amps in your case, times 12v) from your PV, for battery charging and powering loads.

I don't know your exact model and how much PV it can take (or how much PV you have available). So this might not hinder your PV performance anyways. But I really don't see a reason why anyone would disable this setting (or to be more precise: why anyone wouldn't enable it, because it's disabled by default).

 

10 hours ago, meetyg said:

Just another tip: I would suggest you change this to ENABLE.

According to the manual (and my own observations), it enables the inverter to pull maximum PV in order to charge the battery, but also to power any loads.

If it's disabled, you allow it to take a maximum of setting #11 (60 amps in your case, times 12v) from your PV, for battery charging and powering loads.

I don't know your exact model and how much PV it can take (or how much PV you have available). So this might not hinder your PV performance anyways. But I really don't see a reason why anyone would disable this setting (or to be more precise: why anyone wouldn't enable it, because it's disabled by default).

 

I'll try this. I never understood this setting, so i left it in the default state

10 hours ago, meetyg said:

BTW, you have power saving mode ENABLED. Have you tried to put a large enough load (say above 50w) ?

yes, there is always more than 50W of load at any one time

I think I might have figured out what exactly causes the issue, but not the solution.

I don't know if other users face this, but the voltage indicator varies greatly depending on whether the battery is charging or discharging.
for example, it can show 12.9V while charging, but if charging stops and immediately starts discharging, it could go down to 12.3V and vice versa. Not sure what to say about this behavior, but I always observe this.

Now, if the system is recovering from a low DC voltage disconnection, based on whatever value is in setting 19. The system will briefly reboot perfectly, but soon afterward, the voltage will have seemed to go down as it normally does, but now to a value below setting 19 again, prompting the system to shut down.

11 hours ago, Kz_ said:

I think I might have figured out what exactly causes the issue, but not the solution.

I don't know if other users face this, but the voltage indicator varies greatly depending on whether the battery is charging or discharging.
for example, it can show 12.9V while charging, but if charging stops and immediately starts discharging, it could go down to 12.3V and vice versa. Not sure what to say about this behavior, but I always observe this.

Now, if the system is recovering from a low DC voltage disconnection, based on whatever value is in setting 19. The system will briefly reboot perfectly, but soon afterward, the voltage will have seemed to go down as it normally does, but now to a value below setting 19 again, prompting the system to shut down.

The change from charging to dis charging is very normal. That drop from 12.9V to 12.3V is because you are removing the high source(charger) than the battery level. Also you get a drop over the battery internal resistance when you start dis charging. The output value will always be lower when starting a discharge.

12 hours ago, Kz_ said:

for example, it can show 12.9V while charging, but if charging stops

Sorry to bud in here. This battery is a lifep04 as you previously confirmed. What it the battery capacity 100ah(1280wh or 200ah(2560wh)?

 

12 hours ago, Kz_ said:

it can show 12.9V while charging, but if charging stops and immediately starts discharging, it could go down to 12.3V

12.9v for a lfp battery is 3.225v/ cell and 12.3v is 3.075v/cell so this battery is respectively at 30% soc and 10%soc so you have a problem not charging the battery full. You say you charging up to 14v after the charger switch off after CV cycle it should settle to rest voltage of around 13.5v. 

On 2024/04/26 at 7:48 PM, Kz_ said:

21. battery stop charging when grid is available  -- 12.5v

Why are you stopping the charge at 12.5v rather stop charging at 13.8v(100% soc)

Edited May 9, 20242 yr by TaliaB

37 minutes ago, TaliaB said:

Why are you stopping the charge at 12.5v rather stop charging at 13.8v(100% soc)

I just noticed that his stop charging setting is fairly low, as you mentioned. This shouldn't affect the charge cycle (bulk then float). Rather in SBU priority, it affects when to use the battery to supply loads (otherwise from grid).

But, as his setting is low, it might cause some problems.

I like to have mine at 60% SOC (13.2v approximately for a 12v Lifepo4).

@Kz_ In general, I suggest that you change setting to a larger delta between values:

On 2024/04/26 at 8:48 PM, Kz_ said:

low DC cut off voltage – 12.0V

This is fine, as long as it's higher than BMS discharge cutoff by say at least 0.4-0.5v

On 2024/04/26 at 8:48 PM, Kz_ said:

battery stop discharging when grid is available  –- 12.1V

Change this to 12.5v

On 2024/04/26 at 8:48 PM, Kz_ said:

battery stop charging when grid is available  -- 12.5V

Change this to at least 13.2v

Then tell us if the problem is solved. 

Again, if grid is not available, I would expect the inverter to charge via solar. When 12.5v is reached, I suppose that only then it will start inverting (supply loads via battery).

Please change as recommended above and tell us if this solved the problem.

To summarize: Don't expect AC output when grid is not available, until solar has charged to 12.5v or above.