Solax Master & Slave Inverter arrangement not performing

Hope someone can provide a little guidance on this as my installer has been unable to figure this out despite many site visits and attempts to resolve.

I had a single phase Solax X1 hybrid inverter system installed with a Master & Slave arrangement on 2 x 3kW inverters, with 2 x 5.8kWh Triple power batteries (and 1 solar string) linked to each inverter.

I have been having persistent problems with both inverters not delivering the expected level of performance in terms of kWh delivered from the batteries. I would expect from the arrangement in place that the stated capacity of 23.2kWh (5.8kWh x 4) should actually give me somewhere in the region of 20kWh of usable storage when I take off the 12% min SOC that the inverters are set at and also a bit more for the round trip efficiencies. In reality I am getting roughly 15 - 16kWh of usable capacity from the system.

My observations are:

The master inverter (controlling 2 x 5.8kWh batteries) is delivering in the region of 9kWh which is lower than the circa 10kWh expected.
The slave inverter (controlling a further 2 x 5.8kWh batteries) is delivering in the region of 6.5kWh of usable storage, significantly lower than the 10kWh expected.

I can see when I look at the overnight charge cycle on cheap rate that 1 inverter charges for roughly 3 hours and the other inverter charges for roughly 2 hours, which does stack up regarding the capacity seen - 3kW inverter charging for 3hrs & 2hrs = circa 9kWh and 6kWh respectively.

Has anyone come across this scenario or can offer some advice as this has been dragging on too long and I just want a system that works and delivers the manufacturer stated performance (or at least within a few percent of it!!).

Many thanks

I have Solax system, PV array 5.2kw to solax X1 Boost 3.6kw inverter and Solax x1 AC 3.6kw inverter connected to Solax LFP Master Battery with BMS 5.8.kw and Solax Slave LFP 5.8kw giving a total of 11.6kw.

On cheap TOU tariff octopus go for EV and Batteries.

Have you installed the solax iphone or android app and is working, you can see all the details and change various varible settings including for
batteries, charge/discharge ampage 35A all at Default settings, lowest SOC mine is 10%. Battery set to 100% on the Mode of Use... from Self Use to Force Time Use and Octopus Go times 0030hrs-0430hrs are set for both time periods for the X1 AC models.
Charge Percentage % is set at Default 100%.

Daily discharge and charging when solar pv is present, not good this time of year in winter period is roughly 10.2 kw and charges up in about
3 hours... depending on ambient temps outside, in the house/garage, mine are in cold garage (batteries covered by insulation to retain battery temps), and the cold temps effect the charging/discharging.

Plus you incur losses (10- 15%) from AC charging to the batteries DC for every kW added all depending again on the ambient temps for inverter and batteries.

Today in January 2023 charging and discharging at from 200-w to 3680w max of inverter battery temp of around 19'C to plus 20'C by 2'C max

What Solax inverters are your batteries connected to?

Why did you not use one inverter connected to Solax Parallel box using Slave batteries only (max 6-8 batteries depending on configuration)

No Solax Master batteries required in setup.

What is your house consumption usage in kW per day... does that max your battery setup.

To be honest mine are working fine since middle of November 2022 install in UK also.

My worry was after installer installed the battery system, was a constant 200w base load of 2.4kw per day on the Octopus Go, as my inverter
is CT Clamp connected in main meter cabinet on outside garage wall and was aware of this by my Octopus Home Mini connected in the double garage attached to house by the Octopus iphone app which shows Live data for usage in two time periods of 5mins and 30mins, plus Daily Live data for total house consumption in kw per 30min time periods, the Live 5min and 30 min would show Positive import reading of 150w-200w per hour, but now changed some settings in the solax iphone app under Advanced, and now the Octopus Live data shows Negative value form -20w to -150w with the Grid supply.
Confirmed daily monitoring of iphone apps for Octopus Compare and Octopus Watch... for the daily usage in kw and costs, solax system in total is working better than I had expected anticipated.

I did contact the installer and informed him of my base load, his response is working fine, and would try to find time to come and inspect...
alas that has not happened... far too busy imo to provide good customer service after install.

Hi thanks for the reply.

I have:
PV array around 5.5kw
Qty 2 x Solax X1 3.0kw inverter (master & slave)
Qty 4 x Solax Triple Power 5.8kw giving a total of 23.2kw (1 master and 1 slave battery per inverter)

EDF electric vehicle tarrif which allows for low cost charging overnight

I have the Solax iphone App which seems to be working fine

The settings in the App are all fine. Max charge = 100% and Min charge = 12%. This is set slightly higher than I would like as the batteries were tending to discharge down below the minimum of 10% which has implications for the long term life of the batteries...

The system is set for Self Use at the moment and working correctly in terms of charging and discharging at the correct time of day.

My batteries are in the loft space and temperature looks good and stable.

The layout of the system was defined by my installer. As it is a single phase system, you can only have max 3 batteries on 1 inverter, so 4 batteries required 2 inverters.

Everything is working great and doing what it should do, other than the reduced capacity on the batteries as mentioned in the first comment.

PMR said:

Hi thanks for the reply.

I have:
PV array around 5.5kw
Qty 2 x Solax X1 3.0kw inverter (master & slave)
Qty 4 x Solax Triple Power 5.8kw giving a total of 23.2kw (1 master and 1 slave battery per inverter)

EDF electric vehicle tarrif which allows for low cost charging overnight

I have the Solax iphone App which seems to be working fine

The settings in the App are all fine. Max charge = 100% and Min charge = 12%. This is set slightly higher than I would like as the batteries were tending to discharge down below the minimum of 10% which has implications for the long term life of the batteries...

The system is set for Self Use at the moment and working correctly in terms of charging and discharging at the correct time of day.

My batteries are in the loft space and temperature looks good and stable.

The layout of the system was defined by my installer. As it is a single phase system, you can only have max 3 batteries on 1 inverter, so 4 batteries required 2 inverters.

Everything is working great and doing what it should do, other than the reduced capacity on the batteries as mentioned in the first comment.

Click to expand...

Hi PMR, can’t help you but wondered if you can help me. I have similar setup to you but my batteries are 3 x 4.5 KWh on one X1-AC and 1 x 6.3 KWh on the other X1-AC. Of course these are not hybrid inverters, I also have two PV inverters.

Only one of the X1-AC is connected to the system, the second one charges the second battery overnight and I manually change them over each day when one depletes.

Are your two inverters hybrids? If so then I won’t waste your time, but if they’re both X1-AC I’d appreciate it if you would draw a diagram of your CT/Meter connections.

Thanks in anticipation.

My solax X1 AC 3.6 betray inverter for Master and Slave LFP 5.8kW total capacity 11.6kW

Using CT clamp (no meter) to incoming Grid Live between DNO meter and Henley block

CT + to RG45 pin 1 orange/white
CT - to RG 45 pin 4 blue

Position CT clamp in DNO meter box

On the invert AC under Setting>Advanced check Export Control > Meter/ CT

Mine is Checked for CT and Set the Export Control to 0watts

To test put on Kettle for a cuppa to check the inverter is discharging 3000watts
on the AC inverter LCD screen should show
3000watts or less if your solar is running.

To Charge /Discharge battery on like TOU cheap tariff Octopus Go, change Working Mode from Self Use to Force Charge and enter your Octopus Go time in both the Charge Periods.

When Charging you are on Grid for House load When Charge time is Finished the inverter will run the House Load until the next charge period on Octopus Go

Solar PV will charge the batteries on sunny days

PMR said:

Hope someone can provide a little guidance on this as my installer has been unable to figure this out despite many site visits and attempts to resolve.

I had a single phase Solax X1 hybrid inverter system installed with a Master & Slave arrangement on 2 x 3kW inverters, with 2 x 5.8kWh Triple power batteries (and 1 solar string) linked to each inverter.

I have been having persistent problems with both inverters not delivering the expected level of performance in terms of kWh delivered from the batteries. I would expect from the arrangement in place that the stated capacity of 23.2kWh (5.8kWh x 4) should actually give me somewhere in the region of 20kWh of usable storage when I take off the 12% min SOC that the inverters are set at and also a bit more for the round trip efficiencies. In reality I am getting roughly 15 - 16kWh of usable capacity from the system.

My observations are:

The master inverter (controlling 2 x 5.8kWh batteries) is delivering in the region of 9kWh which is lower than the circa 10kWh expected.
The slave inverter (controlling a further 2 x 5.8kWh batteries) is delivering in the region of 6.5kWh of usable storage, significantly lower than the 10kWh expected.

I can see when I look at the overnight charge cycle on cheap rate that 1 inverter charges for roughly 3 hours and the other inverter charges for roughly 2 hours, which does stack up regarding the capacity seen - 3kW inverter charging for 3hrs & 2hrs = circa 9kWh and 6kWh respectively.

Has anyone come across this scenario or can offer some advice as this has been dragging on too long and I just want a system that works and delivers the manufacturer stated performance (or at least within a few percent of it!!).

Many thanks

Click to expand...

I have exactly same issue, 2 x Solax Xi hybrid inverters condigured as Master / Slave, 1 PV string on each inverter. I have 2 x 5.8kWh Triple power batteries linked to the master inverter (only). Power consumed on discounted rate overnight charge calculates as approx 7.2 kW to charge from 10% min SOC to 100%, meaning the 100% capacity for 2 x 5.8kW batteries is only about 8kWh. DIscharge cycle similarly yields well under the nominal 2 x 5.8kWh. I've read somewhere that the batteries should be balanced when installed, but if not will self balance over time. I've had this configuration a few months with no significant improvement, so mayeb self balancing is a myth. Any ideas of feedback?

How many times have you discharged to Default 10%? Which should equate to1160W
My batteries seem now to be balanced better overall since install and use of plenty of full cycle Discharges/Charges.

Also since my install discharging to 10% (numerous times) Default setting (my X1AC 3.6kW inverter charges/discharges max 3680W and only drops Amps when ambient temps are below 16’C. PS you might of noticed yourself from the solax app on the battery setting to be confirmed with local temp and Octopus Home Mini device; cost free but you need to apply for one, it has been very handy for data comparison.

I do think the efficiency of 97% from spec sheet data is on the high side for AC- DC and back DC-AC to house loads after some time monitoring solax app data (way off for feed-in and usage as well as total daily use) compared to my Octopus Home Mini with Electric Daily Live Data every 5 mins or 39 mins intervals including Gas coverage Live data on it aswell imho.
Plus colder day/s temps all result in different daily usages in higher losses for the inverter for both discharge/charge cycles for the 24 hr periods.

My battery system is working fine in last two months only Imported 16kWh and 12.3kWh
from Grid respectively apart from my EV and batteries on off peak tariff Octopus Go.

Don’t forget Contiuous base load of the inverter @ 50W / 0.05kWh for 24 hrs is 1.2kW or even higher to maintain the Grid voltage incoming to near zero import alll the time which never happens you will get some import when house loads change during the same period. CT clamps respond quicker than Solax Eastron SDM 230 Modbus meter
where more import is accounted for for slower response to demand.

My CT clamp is always above -66W to prevent import by the inverter so when Kettle go a cuppa is on the response between Inverter+ batteries to Grid import is 3W

JayHaich said:

I have exactly same issue, 2 x Solax Xi hybrid inverters condigured as Master / Slave, 1 PV string on each inverter. I have 2 x 5.8kWh Triple power batteries linked to the master inverter (only). Power consumed on discounted rate overnight charge calculates as approx 7.2 kW to charge from 10% min SOC to 100%, meaning the 100% capacity for 2 x 5.8kW batteries is only about 8kWh. DIscharge cycle similarly yields well under the nominal 2 x 5.8kWh. I've read somewhere that the batteries should be balanced when installed, but if not will self balance over time. I've had this configuration a few months with no significant improvement, so mayeb self balancing is a myth. Any ideas of feedback?

Click to expand...

I have exactly the same issue, 2x Solax 5.8Kwh giving me about 7.5-8KWh. So losing around 2.5Kwh/day. Have you managed to sort this issue out? I am trying with Solax but no luck yet.

I have the feeling after I got Octopus Home Mini to show Daily Live Data at 5mins and 30 mins intervals....
but also shows if import or export is taking place with your system.... I noticed the 2.4kW is 0.1 x24 hrs is my daily house load
being imported not covered by batteries... until i changed my CT direction to negative and Live data showed 0 watts
or 15 negative value... will put some screen shots up of daily usage from iphone.

Last week called Solax UK about anomaly with the app with over 6kw or 12kw import when charging my solax 11.6kw batteries and
EV car to 30kw for four hours at 7.5kw Hypervolt.... funny thing is I check the Octopus Home Mini Live Data and both times showed
import of 4.2kw for battery charging and house load... and 11.5kw for EV charger 7.5kw plus batteries at 3.6kw and house load
so was relieved that the app was overeading AC and Grid power.... Solax replied that a firmware updates where available for both
the Solax X1 Boost and Solax X1 AC inverters, which where done remotely online by Solax... but the App is always either down not long
or reporting Bogus power figures, since systems were installed....

For Hybrid if you notice house load not being covered by batterie.... check Settings>Advanced>PGrid Bias> Default is inverter
change to Disable... check your Live house load.

FVScimitar said:

I have the feeling after I got Octopus Home Mini to show Daily Live Data at 5mins and 30 mins intervals....
but also shows if import or export is taking place with your system.... I noticed the 2.4kW is 0.1 x24 hrs is my daily house load
being imported not covered by batteries... until i changed my CT direction to negative and Live data showed 0 watts
or 15 negative value... will put some screen shots up of daily usage from iphone.

Last week called Solax UK about anomaly with the app with over 6kw or 12kw import when charging my solax 11.6kw batteries and
EV car to 30kw for four hours at 7.5kw Hypervolt.... funny thing is I check the Octopus Home Mini Live Data and both times showed
import of 4.2kw for battery charging and house load... and 11.5kw for EV charger 7.5kw plus batteries at 3.6kw and house load
so was relieved that the app was overeading AC and Grid power.... Solax replied that a firmware updates where available for both
the Solax X1 Boost and Solax X1 AC inverters, which where done remotely online by Solax... but the App is always either down not long
or reporting Bogus power figures, since systems were installed....

For Hybrid if you notice house load not being covered by batterie.... check Settings>Advanced>PGrid Bias> Default is inverter
change to Disable... check your Live house load.

Click to expand...

What does the PGrid Bias setting do? Another of these mystery settings which is hard to make sense of...

Constant import for your inverter from Grid is my understanding for Solax X1 Hybrid inverters

Sorry to jump in on this thread but I have a different issue but related. My installer has told me you can't set up 2 inverters onto one user account despite their being a master and slave set up. Has anyone been able to set up two Solax inverters on one account? He has said the only way around this is to have 2 separate accounts one for the master and one for the slave.

Jmartinscott@btinterne said:

Sorry to jump in on this thread but I have a different issue but related. My installer has told me you can't set up 2 inverters onto one user account despite their being a master and slave set up. Has anyone been able to set up two Solax inverters on one account? He has said the only way around this is to have 2 separate accounts one for the master and one for the slave.

Click to expand...

My system comprises of:

1/ On my garage roof: Solar array of 4.3kWp, X1-Hybrid 3.7 G4 inverter, One master and one slave battery - both 5.8kWh
2/ On my house: Duplicate setup to Garage

I have the House Inverter set to 'Master' and a Cat 7 commination's cable connects the two inverters. On my Account, I have one Site and two Inverters. So in answer to your question: Yes you can have two inverters setup on one account.



However, they aren't working correctly yet!!! The Master system is working fine but the slave system just does it's own thing and happily and randomly charges and discharges with no relation to house demand. It also appears to be fighting with the Master Inverter (i.e. The Slave batteries charge from the Master Batteries and vice versa!)

The system was only installed 3 days ago and so I'm hoping that this will be sorted out soon. In the mean time, I've turned off charging from the grid temporarily while SolaX review the setup/settings remotely.