Voltronic Axpert Inverter Programming: What to Set and Why

Programming a Voltronic Axpert inverter comes down to a handful of decisions, and every one of them has a right answer that depends on your battery, your grid and your loads. The program numbers on the screen change from one Axpert generation to the next, so this guide does not list them: it sets out the decisions, with the values the product records state, so that you know what to enter when your unit's own menu asks for it.

Before you open the settings menu

Write down three things: the exact model on the label, the battery you connected, and what feeds the AC input, grid or generator. The records in our catalogue show how the settings are reached. The Axpert King II TWIN states a detachable LCD control module and an AC/Solar input priority configurable via LCD setting. The Axpert MAX II Duplex 11K states a charging current adjustable via LCD operation and mobile APP, with built-in Wi-Fi.

If the inverter is not sized for the house, no setting will fix it. Check the load first with the sizing calculator.

Decision 1: which source feeds the loads first

The Axpert King II TWIN record calls this the AC/Solar input priority. The MAX II Duplex record goes further: an AC/PV output usage timer and prioritization, and two independent AC power sources that are connected and switched automatically. The choice is simple to state. Where the grid is weak or costly, solar and battery come first and the AC input is the reserve. Where the battery exists only for outages, the AC input comes first and the battery stays full.

Decision 2: the AC input range

The Axpert MAX II Duplex 11K record gives two input ranges, named after what they protect:

In both ranges the inverter leaves the AC input above 280Vac±7V and returns at 270Vac±7V. The UPS range suits computers and electronics, which tolerate little sag. The Appliances range suits a generator or a grid whose voltage dips often: the inverter stays on the AC input instead of dropping to the battery at every dip.

Decision 3: the charge current

This is where the inverter record and the battery record must be read together. The Axpert MAX II Duplex 11K can push 150A of solar charge current and 150A of AC charge current. The LIO 4810 battery record states a maximum charge current of 100A (0.5C), and the LIO 4805 states 50A. With a single LIO 4810 on a MAX II Duplex, the charge current setting has to come down to 100A or less. The LIO II-4810 record is more explicit still: charging current 100 A maximum, 30 A by default.

Decision 4: the battery voltages

Three inverter values frame the battery. On the MAX II Duplex 11K record:

• floating charging voltage: 54Vdc;
• low DC cut-off voltage: 44Vdc;
• high DC cut-off voltage: 63Vdc, with a cold start voltage of 46.0Vdc.

Now the battery side. The LIO 4810 record states a charge voltage of 52.5 ± 0.1V and a full discharge voltage of 34.5VDC. The inverter's 54Vdc float is above the 52.5 V this battery asks for, so the charging voltage must be set to the battery's figure rather than left as it is. The LIO II-4810 states a full charge voltage of 56 V ± 0.1 V, a full discharge voltage of 42 V and an operating range of 40 to 56 VDC, so 54Vdc and 44Vdc both sit inside its range.

Where the inverter and the battery share a communication link, the battery management system supplies these limits itself. The King II TWIN record states a reserved communication port for BMS (RS485 or CAN-BUS); the LIO 4810 has an RS485 port, the LIO II-4810 RS485 and CAN.

Decision 5: equalization

Several Axpert records, among them the Axpert VM III TWIN 6K, state a battery equalization function that extends battery lifecycle. Whether to switch it on is the battery's decision, not the inverter's: follow the charge method on the battery's own datasheet.

Decision 6: units in parallel

The MAX II Duplex 11K runs up to 6 units in parallel over a CAN link; the King II TWIN up to 9. Every unit in the group must carry the same settings, and the fault list says why:

• 71, firmware version inconsistent;
• 83, battery voltage detected different;
• 84, AC input voltage and frequency detected different;
• 86, AC output mode setting is different.

When a code points back to a setting

Three codes on the Axpert MAX II Duplex fault list usually send you back to the menu rather than to a repair bench. Code 03, battery voltage too high, has the cause "battery is over-charged": compare the charging voltage with the battery record. Code 04, battery voltage too low, asks whether the low cut-off suits the battery. Code 07, overload time out, means the inverter stayed at 110% load until the timer ran out: reduce the load. The same two-digit code means something else on another Voltronic model, so read it on your own model's page in the error-code lookup.

Where the values are printed

Every figure above is on the family datasheets: Axpert MAX II Duplex, Axpert King II TWIN and LIO 4805 and 4810. For the hybrid range, the steps are in our guide to configuring an InfiniSolar inverter.