I just buy a Multiplus II GX and it turns out that it can't start without AC Input (Grid/Generator).
When I am off-Grid I would like the opportunity to turn off the inverter on the switch and back on when i need power ...
The batteries are fully charged (48v/200Ah, using mppt 250/100).
what am I doing wrong? How do I turn the “MP II GX” on?
As nickdb suggested the error was a failed firmware updat….-on the other hand, it is not necessary to remove any internal cable to connect the mk3 adapter.
Unfortunately, it was not possible to perform a remote update, because the GX is apparently not powered by the battery, but by the inverter!
maybe it will work if AC is connected.
thank you, nickdb!
How have you configured the inverter?
Did you program the correct battery and charger settings?
An inverter will happily run off charged batteries and no grid.
Batteries (BMS) can trip when connected to a multi as the initial surge to charge the caps may overwhelm the BMS.
Alternatively the parameters on the inverter are configured incorrectly so it does not know the battery is at the right voltage.
The MP is configured with a lithium battery, according to the supplier's specifications - by the way, as the "Victron MPPT" configuration (since it's the same battery ;o).
Am I to understand that neither the GX part nor the inverter part can start if the battery is not 100% charged?
Do you have a guide?
As long as the battery is above the inverter cutoff/restart voltages - which have to be manually set - and above ESS cutoffs then it will start.
What will prevent it is if the BMS has disconnected, for example physically connecting the battery to the inverter or turning the battery pack on. This can result in a surge that trips the battery or causes the BMS to block, pre-charging solves this.
What firmware is the inverter?
There are known power on issues with older firmware that requires an update.
While the inverter appears off, in this state it can still be reached with a mk3 adapter and updated with veflash.
BMS is not disconected and the battery voltage is far over inverter cutoff.
ESS is disbaled, do I need an "Energy Storage System" in an off-grid environment?
I don't think is could be a pre-charge problem since it's the battery isn't disconnected. The inverter is turned off (and on) from the switch.
I have tried with firmware 3.12 and 3.20-30.
No, the inverter is not reachable with MK3 adaptor, before AC is connected.
Do you have a link to a guide on how to setup the "PM II GX"?
ESS isn't actually supported offgrid.
3.12 and 3.20 is the GX software version, the multi has its own unique firmware that is updated separately.
The GX model is a little quirky as the GX is embedded within the chassis rather than an external model, which imo, is just easier.
To use the mk3 you need to disconnect the internal vebus connection from the GX as both can't be connected together.
The setup instructions are all in the manual which you can find here:
https://www.victronenergy.com/media/pg/MultiPlus-II_GX/en/index-en.html
If you keep struggling you may need to take it to your supplier for a benchtest.
Or, if you are up to it, carefully remove the cover and make sure nothing is loose or disconnected inside.
Thanks for your prompt reply.
But I have the manual, I asked for a guide to set up the MP, (Ve.configure guide,specific to MPII GX, I think).
Do you have experience with MP II GX...? According to the manual you sent the link to and my little experience, you can communicate with the MK3 -(provided AC is connected).
The manual does not mention an option to disable internal GX.
My other question was whether I have to configure ESS when my system is not connected to the grid?
It is configured like any other multi, the best reference is the veconfigure guide, but since you don't need the ESS assistant you can use the victron connect app instead which is more intuitive.
If you pop the cover there is an internal connection from the embedded GX to the Inverter for the vebus. It is what used to be disconnected when an external cerbo was going to be used.
The inverter should be responsive to a mk3 when powered from DC provided it is on.
Is the GX LCD also blank? That should at least show signs of life if there is power.
Can only suggest you try an alternative source of DC power, open it yourself, sometimes things come loose, or take it for testing.
The switch position is at position 1 (on) not 2 (charger only)?
@nickdb just a thought on this one, could there be a switch turned off that prevents the Multiplus from powering up from battery only, or a missing interlock? Just a thought. 
Thank you for your contribution.
No missing interlock.yes, that switch.
When switched off, the inverter cannot be switched on again (without AC).
How do you switch it on again (without AC connected)?
@claus@hemdrup.dk What voltage do you have measured on the DC contacts on the Multiplus with the batteries connected and the Multiplus turned on? By any chance do you have AES enabled in VE Configure and do you have 'shut-down on SOC turned on, if so what are your settings? Also do you have anything connected to AUX1?
A screenshot of your VE Configure settings would provide some helpful info.
