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Axpert King 5KV - Solar priority setting


Roentgenzap
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Hi All, 

So, my setup: 3 x Axpert King 5Kva in parallel (working as single phase) (Firmware 71.9) 16 x Narada 200ah batteries (Narada 12ndt200) setup in 4 x 48V parallel.  28 x 370W panels (2s14p split 5/5/4 between the inverters). 

My question relates to setting 16 - Solar energy priority on the Axpert King. Options for this setting:

SBL / UCB - Solar energy for battery first, Allow utility to charge (default)  //  SBL / UDC - Solar energy to battery first, disallow utility to charge  //  SLB / UCB - Solar energy for load first, Allow utility to charge   // SLB / UDC - Solar energy for load first, disallow utility to charge

 

Now I fully understand the functionality to enable or disable utility battery charging - that makes complete sense. 

The problem I have is between the SBL and SLB settings - what difference does it make in practical terms? When PV power is more than load, the batteries will charge with the excess power available (no matter SBL / SLB option). When PV power is not enough to supply load, then the shortfall will be taken from the batteries or grid, depending on operating mode setting (SBU or SUB respectively). 

From what I can see, what difference does the SBL / SLB setting make, or am I missing something?

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51 minutes ago, Roentgenzap said:

From what I can see, what difference does the SBL / SLB setting make, or am I missing something?

I have a different model Axpert, but from I have seen the difference is the following:

  • SBL / UDC - PV priority will be for charging the batteries, grid will be used to power the loads. Only if PV is higher than max PV charge current will excess PV be used to power the loads
  • SLB / UDC - PB priority will be for powering the loads. Any excess PV will be used to charge the batteries

If you want to maximize your savings and are confident that you have sufficient excess PV to fully charge your batteries over the course of the day, you should run in SLB (which to my understanding is the same as SBU on my Axpert)

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1 hour ago, Roentgenzap said:

what difference does the SBL / SLB setting make

I don't own a King, but this is how I interpret what the manual says. In SBL priority, "solar energy charges the battery first". In SLB, "solar energy provides power to the load first".

In a King, net power to/from the battery can be controlled by adjusting how much power the AC-in (utility) provides to the load. So in SLB mode, even though you have power to charge the battery, the system can lower the utility power by the amount it would have charged the battery, thus "stealing" the power for the loads.

Perhaps an example, ignoring losses for simplicity. This is the way I imagine it; I could easily be wrong. Load 600 W, available PV 1000 W.

With SBL priority, the system would power the 600 W for the load from the utility, so that all the 1000 W charges the battery. As Wolfandy says above, if the battery can only take 800 W, then 200 W is available to power the loads, and the other 400 W comes from the utility. This is handy if you are expecting load shedding, so your priority is to charge the battery.

With SLB, it would not use any utility power in this example, so 600 W goes to the load, and 400 W charges the battery. This is handy if you aren't expecting load shedding, and want to minimise utility energy use.

Would any King owners care to confirm or deny?

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30 minutes ago, Coulomb said:

I don't own a King, but this is how I interpret what the manual says. In SBL priority, "solar energy charges the battery first". In SLB, "solar energy provides power to the load first".

In a King, net power to/from the battery can be controlled by adjusting how much power the AC-in (utility) provides to the load. So in SLB mode, even though you have power to charge the battery, the system can lower the utility power by the amount it would have charged the battery, thus "stealing" the power for the loads.

Perhaps an example, ignoring losses for simplicity. This is the way I imagine it; I could easily be wrong. Load 600 W, available PV 1000 W.

With SBL priority, the system would power the 600 W for the load from the utility, so that all the 1000 W charges the battery. As Wolfandy says above, if the battery can only take 800 W, then 200 W is available to power the loads, and the other 400 W comes from the utility. This is handy if you are expecting load shedding, so your priority is to charge the battery.

With SLB, it would not use any utility power in this example, so 600 W goes to the load, and 400 W charges the battery. This is handy if you aren't expecting load shedding, and want to minimise utility energy use.

Would any King owners care to confirm or deny?

In theory you are correct and it works in SBU mode, in reality the inverter does just what it wants in SUB mode.

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17 minutes ago, wolfandy said:

I have a different model Axpert, but from I have seen the difference is the following:

  • SBL / UDC - PV priority will be for charging the batteries, grid will be used to power the loads. Only if PV is higher than max PV charge current will excess PV be used to power the loads
  • SLB / UDC - PB priority will be for powering the loads. Any excess PV will be used to charge the batteries

If you want to maximize your savings and are confident that you have sufficient excess PV to fully charge your batteries over the course of the day, you should run in SLB (which to my understanding is the same as SBU on my Axpert)

Hi

 

The SBL / SLB setting is separate from the operating mode (SBU / SUB) in the Kings. 

You can have either SBL or SLB enabled and operate in SBU or SUB mode. Hence my confusion. 

 

25 minutes ago, wolfandy said:

SBL / UDC - PV priority will be for charging the batteries, grid will be used to power the loads. Only if PV is higher than max PV charge current will excess PV be used to power the loads

That may be the case if operating in SUB mode. With the Kings ability to blend AC/PV/Battery power, does it make a difference though? if (PV power) + (Ac power) = Load + battery charge, does it matter where it each one is assigned to, as total power usage will be the same? The only impact I can forsee in this circumstance would be the charging rate (limited to PV availability). 

If operating in SBU mode, then there will be no AC usage unless battery voltage is below cutt-of or back-to-grid voltages. Should PV power be insufficient for loads, then battery will be consumed until battery cut-of value or back-to-grid voltage has been reached. 

 

32 minutes ago, Coulomb said:

With SBL priority, the system would power the 600 W for the load from the utility, so that all the 1000 W charges the battery. As Wolfandy says above, if the battery can only take 800 W, then 200 W is available to power the loads, and the other 400 W comes from the utility. This is handy if you are expecting load shedding, so your priority is to charge the battery.

With SLB, it would not use any utility power in this example, so 600 W goes to the load, and 400 W charges the battery. This is handy if you aren't expecting load shedding, and want to minimise utility energy use.

Once again, this would only be if operating in SUB or USB mode. 

 

So if I re-hash this, then operating in SBU mode (and given that the battery voltage is above back-to-grid and cutt-off settings), then SBL / SLB will basically be the same. 

Only when operating in SUB mode, then SBL / SLB comes into play when consuming utility with impact on the battery charge rate (depending on PV availability). This obviously is further confounded when taking the UCB / UDC setting (and max AC charge rate setting) into account.?

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