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Solis RHI 5kw + Pylontech US500 not stopping discharge at defined SOC

K-Tech

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Sep 30, 2022
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Hi everyone,

This is driving me mad. Solis inverter Over discharge SOC set @30% but when this SOC is reached the system still continues to discharge, albeit at a limited rate of approximately 130W. It will continue to do this all through the night. This morning battery SOC was at 12% when I woke up so manually stopped the battery.
It's as if the battery will not go into idle as I've also noticed that the battery can be 100% SOC and the system will be exporting 2kw after demand from the house is accounted but still the battery is discharging 130W.
Inverter set to self use. Timed charge/discharge etc switched off.
System works great apart from this with current daily energy import around 0-1kWh.

Any suggestions welcomed
 
Is that 130w draw not perhaps used to power the inverter itself?
No it's a grid tied inverter so it will be primarily powered by the DC from the PV. If it was off grid that would be an unusually large and impractical standby current.
 
Battery's have self-discharge due to the balancers / BMS doing their thing which is powered internally by the battery, you will see the battery SOC go down. On my 10kw BYD, it needs to top off the battery twice a day due to this, so around 4% a day of the rated energy ( its about 130 watts on the BYD packs, but this isn't unique to BYD )
 
Battery's have self-discharge due to the balancers / BMS doing their thing which is powered internally by the battery, you will see the battery SOC go down. On my 10kw BYD, it needs to top off the battery twice a day due to this, so around 4% a day of the rated energy ( its about 130 watts on the BYD packs, but this isn't unique to BYD )
As mentioned in the original post, it is not respecting the max discharge SOC setting, not just loosing energy from self use. In fact I have seen it go into idle at 30% SOC twice, but only for an hour or so , and then I've noticed as the cell voltage creeps up it then starts to discharge again and ignore the SOC. Also, at 130w continuous BMS use the Pylontech would use over 60% of its capacity in a 24hr period of no charge/discharge. This would be an obvious design flaw, hence the ability to be put into idle, which is not happening either at full charge with no demand or after max discharge level has been reached with no available charge. Once max discharge SOC has been reached the BMS should put battery into idle until charge is available otherwise the max discharge SOC will be breached due to BMS usage and the whole concept of protecting over discharge becomes null and void.
See current state. The battery should be in idle now. There is no reason to be discharging 170w continuously. This is not BMS use, and I would hope BMS use would not be shown in energy flow schematics. But this is my first play with a Solis Hybrid inverter and also Pylontech batteries. Luckily this is a test before potentially rolling out to customers otherwise I imagine this would be causing me more stress than it already is?
 

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Starting to think this might be related to the Acrel meter at the grid position. Just dropped the grid connection and the battery goes straight into idle as it should when there is no demand
 

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Inverter and BMS - do they have any communication between them?

"the BMS should put battery into idle" - Only thing BMS can do is shut off DC output (no power reaches inverter) or request inverter to stop.

My guess (not being familiar with either) is inverter stops discharging battery when it sees a voltage it associates with 30% SoC. When voltage drifts back up, it again draws down to that voltage. If inverter doesn't keep track of current in/out of battery, voltage is all it knows.

BMS I assume is where you're getting 30% and 12% SoC readings.
I think 30% is higher than where voltage would reliably detect.

Communication would be preferred.
A voltage distinctly into discharge knee might serve as reliable minimum for inverter to stop. (If you want to to stop with more reserve in the battery, e.g. to keep things running when grid fails, need communication with BMS or other device tracking charge in/out.)
 
Inverter and BMS - do they have any communication between them?

"the BMS should put battery into idle" - Only thing BMS can do is shut off DC output (no power reaches inverter) or request inverter to stop.

My guess (not being familiar with either) is inverter stops discharging battery when it sees a voltage it associates with 30% SoC. When voltage drifts back up, it again draws down to that voltage. If inverter doesn't keep track of current in/out of battery, voltage is all it knows.

BMS I assume is where you're getting 30% and 12% SoC readings.
I think 30% is higher than where voltage would reliably detect.

Communication would be preferred.
A voltage distinctly into discharge knee might serve as reliable minimum for inverter to stop. (If you want to to stop with more reserve in the battery, e.g. to keep things running when grid fails, need communication with BMS or other device tracking charge in/out.)
I see what you're saying about SOC calc and voltage. Pylontech require max 30% DOD for warranty purposes, but I'm starting to realise that maybe their "warranty" isn't worth much. Also, it seems the BMS determined that 30% SOC was at around 48.6V last night, but then continued to discharge until I woke this morning when realised it was at 12% SOC at 48.2 and switched off until the sun came up. Also to confirm, the LEDs that indicate battery state were still showing discharge at this level, whereas if it was functioning properly the BMS should have put it in idle until charge was available.

As far as I am aware the idle state should be no inverter to battery/cell connection but BMS still active and reporting voltage/SOC etc.

Maybe I'll try setting under Voltage to 48.6 and see what happens
 
Did you manage to find a solution at all?

I am currently facing the same issue. My batteries will be 70% charged when I go to bed and, despite nothing really being on, discharge to 30% by morning.

When it hits the discharge limit the drain does drop but it doesn’t stop.

It’s just waste of power ?

Thanks in advance!
 
I see what you're saying about SOC calc and voltage. Pylontech require max 30% DOD for warranty purposes, but I'm starting to realise that maybe their "warranty" isn't worth much. Also, it seems the BMS determined that 30% SOC was at around 48.6V last night, but then continued to discharge until I woke this morning when realised it was at 12% SOC at 48.2 and switched off until the sun came up. Also to confirm, the LEDs that indicate battery state were still showing discharge at this level, whereas if it was functioning properly the BMS should have put it in idle until charge was available.

As far as I am aware the idle state should be no inverter to battery/cell connection but BMS still active and reporting voltage/SOC etc.

Maybe I'll try setting under Voltage to 48.6 and see what happens
Your voltages don't sound right... pylontech are 15cells, so 48v should be about 50% SOC.

I've seen the Solis reduce battery draw to a low (but not zero) value if the voltage is below its undervoltage limit, but should cut off when SOC discharge limit is reached.

Does pylontech console port show anything useful?
 
I have same problem (Solis inverter not respecting the SOC limit that is set). This seemed to fix itself after a period of repeatedly trying to manually reset it.
Then installed a second Pylontech battery and am back to square one with no fix happening this time. Batteries go down to 10% with 30% SOC set; not good.
Am I likely to get any response if I raise this with Solis?
 
Does it stop at 10%? Sounds OK as Pylontech claim 95% DoD. 30% sounds too high.
 
Does it stop at 10%? Sounds OK as Pylontech claim 95% DoD. 30% sounds too high.
I've not seen it below 9%, so it probably does stop at 10% (when it was working properly it tended to overshoot by a few percent the 20% SOC that was set at that time; I can understand that because the voltage drop with SOC is very shallow on this particular Li battery chemistry).

I would like to set SOC to 40% for winter use, because I have two batteries which would otherwise be permanently poorly charged during winter (or I may turn off one of the batteries to enable what little PV there is to maintain the remaining battery at a higher state of charge).
Sure, the new Pylon LiFePO batteries are supposed to be good for 95% DOD, but life will be extended if this ability isn't exercised regularly; this was another reason for doubling battery capacity i.e. to give the batteries and easier and longer life.

Solis has issued a ticket number, so fingers crossed they get back to me with something positive. The inverter (RHI-3K-48ES-5G) software could be at least described as quirky!
 
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All sounds so much firmware issue

Got a Solis S5-EH1P with 2 Dyness A48100.
At night, as a result of normal discharge of the batteries, when the battery reaches the SOC I’ve specified in the Solis to stop discharging and use the grid, the batteries “leak” 62w constantly until it gets to the force charge parameter and then starts charging.

908F6CD1-AA53-44DC-B13B-089AEC1F5AF8.jpeg

My SOC setting is 16%. But if it were 20% it would be also ignored. :(
This has to be software fixable. Counterproductive.

Only once, a week back, saw the battery icon with a grey color in 13% and apparently idling and 0 kw as it should be triggered by the inverter.

I bet you there are loads of people with this issue but haven’t noticed. Please do report if you hear anything towards a solution here.

Solis is very obscure on regards firmware versions and models, if they release a solution it won’t be effective in all inverters unless they apply a firmware update remotely and individually. I just hope it can be fixed toying with settings, no luck so far for me.
 
I have just set up my diy battery with Seplos BMS and an AC coupled Solis-3.0K-RAI-48 and have observed the same parasitic drain issue. Thanks to this thread I can assume the Solis is likely the culprit :)

I have set the SOC discharge limit to 15% on the Solis and the SOC discharge warning to 15% on the Seplos BMS with the actual cut off at 5% on the Seplos BMS.
Here is what happens:


The Solis drains the battery until 15% is indicated on the Solis information screen(under bms menu), at this point the current drawn from the battery is showing as zero on the Solis BMS info menu (proves canbus is working).
However the Seplos BMS actually shows 15.43% SOC and 0.65A being discharged.

This indicates perhaps a rounding error in the CAN comms between battery and inverter?

The 0.65A parasitic discharge continues until the Seplos BMS indicates 14.87% SOC (Solis showing 15% throughout).
At this point the Solis begins to charge from the grid at 4.85 battery amps as shown on the Seplos BMS screen until the Seplos BMS shows 15.5% SOC. At this point the battery flip flops from charging at 4.85A to the occasional discharge while hovering around 15.5% as shown on the Seplos BMS.

It seems that the battery for some reason isn't going into standby but the Solis is at least attempting to keep to the discharge SOC setting.
As K-Tech points out, briefly shutting off the grid isolator sends the battery to standby.
I'm not going to lose too much sleep over it but i'll be interested to see if a resolution is found.
 
Solis must do a better job with the firmware, is not only the wasted energy, is the fact the batteries are overused when there is no point, thus reducing the longevity of the batteries and inverter.
 
This morning my battery wouldn't charge. I switched it off and on again and did the same with the inverter grid isolator. It's all working ok now.
I would love to keep a close eye on this but I'm going away to work for a fortnight :cry:

Feels like the parasitic drain is keeping my battery in the discharge mode rather than allowing it to go to standby mode. I think the Seplos needs the discharge to go below 0.7A before it goes into standby and the Solis draws 0.65A, it's all a bit tickly.
 
...The Solis drains the battery until 15% is indicated on the Solis information screen(under bms menu), at this point the current drawn from the battery is showing as zero on the Solis BMS info menu (proves canbus is working).
However the Seplos BMS actually shows 15.43% SOC and 0.65A being discharged.

This indicates perhaps a rounding error in the CAN comms between battery and inverter?...

0.65A at around 48V would be about 30W, which IIRC is about the power the Solis uses (assuming no PV input) to keep it running - that sounds about right to me. I would also assume that the Solis info screen would only show battery power being inverted and not just the DC consumption to keep it running.

You could set the re-charge SOC to say 10% to avoid the on-off charge/discharge.
 
Hello,
I have similar problems with the standby consumption of the Solis.
Only with the difference that I have additionally activated the backup mode. In the mode, the standby consumption goes to zero after he has recharged once at night from the Grid.
Unfortunately the inverter refuses to charge from the PV next morning. In Self Use
mode it works without problems. There is also enough PV power
available!

My settings:
SelfUse on --> min-SOC 20% Force-Charge 15%; Backup on --> Backup-SOC
30%

It discharges to 30% after Backup Mode is activated. After that
the battery is discharged with about 30W (measured). At 27% it recharges from the
Grid and switches off the battery completely at 31% (0A). The Solis is
now supplied with approx. 25W from the Grid. (measured with extra Eastron
counter between Solis and Grid) As far as completely satisfied with the
behavior. Unfortunately, it no longer charges the battery at all. Backup mode off and on fixes the problem until the next night...

Furthermore, the display of the charging power and the house consumption is
incorrect. It is displayed that four times as much is discharged as
is charged! Discharge current of the battery from BMS in standby measured 0.55A. The Inverter
shows 4A. Thus, the Inverter shows a permanent discharge power of over 200W!

FW: 3A0030
Model: 3103
 
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