How to set up the timer to charge the batteries at night – Off Grid Conversol 8kW Max & Max-II

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How to set up the timer to charge the batteries at night – Off Grid Conversol 8kW Max & Max-II

This is a simple step-by-step guide on how to program your off-grid inverter to charge from the grid at specific hours. In order to use low-cost energy tariffs at night, it is important to adjust the settings of the inverter accordingly. This guide is applicable to Conversol Off-grid inverters MAX and MAX-II 7.2kW, 8kW, and 11kW.

This system does not require any paperwork or special license to operate because the inverter is off grid and does not feed back to the grid any power. When the batteries are low the grid will “see” the inverter as any other appliance in the house or as a charger that demands power. For that reason this set up is free from complicated contracts with the electricity suppliers.

How the system works

  1. Charges from Solar First and then from Utility
  2. If the load exceeds the capacity of the inverter then the system goes in by pass mode – The utility supplies all the power
  3. If the energy stored in batteries is low and power from solar is low too, the inverter will go in bypass mode. The grid will charge the batteries
  4. The timer will be set to charge from 12:30 to 4:30  am using the Octopus GO tariff (available in the UK)

To achieve the operations in steps 1-4 please follow the steps below

  1. Prog.01 SBU
  2. Prog.16 OSO  – Only Solar
  3. Prog.99 USB 00 04  or 00 03 (It’s due to the Timer setting is based on “Hour”. 00 04 means 00:00AM~04:59AM is USB or 00 03 which means 00:00AM~03:59AM is USB)
  4. Enable auto restart when an overload occurs in menu 06

Prog.01 at SBU. When the battery voltage is less than the setting of Prog.12 then switch to Line mode. The charger source is defined in Prog.16. If you do not need the AC to charge the battery then set it to OSO. However, if the battery voltage is low and the battery BMS asks for forcing charging then the AC would still charge the battery for a period of time till the battery BMS stops forcing charging. If the SNU is selected in menu 16, then the AC will charge the battery in Line mode.

In SBU mode the inverter may return to AC Line Mode due to low battery voltage, then the PV energy will only be used to charge the batteries (if lithium batteries the voltage is around 53Vdc), until the next battery discharge cycle.


If the timer setting is set to SNU (solar and utility) for 12  04, it means it will charge from utility between 12am to 4am

You MUST set Prog.16 firstly then do the Timer setting later. 12 16 means 12:00 to 16:59 is SNU and out of this time slot is OSO

What happens after an overload condition?

If an overload is detected and the auto-reset function is disabled, the inverter will go into Line-Mode (back to the utility), this is a protection feature in case the overload is frequent and the inverter should stay in bypass until it is reset manually. To continue as normal back the battery/solar mode, the Over-Load function should be set to “auto reset automatically”. Check menu 06

Timer setting for charging 12am to 4am – Menu 99

Inverter is AC Line Mode- The grid charges the batteries


NOTICE  CSO means the AC will charge the battery when PV is not available

Example with two different source priorities:  SNU between 01 and 06 time then going to OSO  between 07 to 00.  It means the AC charger works within 01:00~06:59.