Hi everybody, I've added a second Multiplus ('Generator') that feeds the 1st Multiplus, this to add more power during peak AC moments.
All is working great since a week or so but when I just checked VRM I noticed strange numbers.
The Generator shown in VRM is the added Multiplus, why does it says 1781W when the main loads are 446W?
I went home and found the new Multi (Generator in VRM) with cooling fans on, plugged the mk3 in and saw this:
Although AC loads in VRM said 446W, I still checked the house for any loads, nothing to find that could cause a 9,4A load.
So I plugged in an electric heater (3kW):
Unplugged the heater:
All looks great now, but I have no idea what caused this behavior.....
Well, we're over an hour further and again, odd numbers which doesn't make sense to me:
If you connected the two Multi's in series, to which one is the GX device connected to? The Multi's where not designed to be connected in series. This is likely the cause of your strange readins.
If you want extra power, you need two (or more) identical Multi's and connect them in parallel. Before experimenting with this though, be sure to read up on how to do this as it's easy to make errors which affect performance.
There is plenty of documentation and training in the Victron websites. Reading "Wireing Unlimited" would helpo a lot also.
The 'Old' Multi was and still is connected to the Cerbo GX.
Both Multi's are identical and will certainly look into parallel, thanks for this advice.
Call me a bit stubborn, sorry, but I don't see the difference between a real Generator being driven by petrol or a 2nd Multi driven by a battery, both being connected to the AC-in of a Multi. I mean, voltage going in the old Multi, does it really matter where the voltage is coming from?
I have just updated all device with latest firmware, let's see if this makes a difference, if not I will definitely be going for parallel as you suggested.
Thanks again for taking you time to reply, much appreciated !
I agree it would be better to connect them in parallel, but maybe the OP can't parallel them as they may be different sizes or hardware versions.
Thanks, the only reason I've connected them this way is that is was/is much quicker than parallel. Both Multi's are 48/5000/70-50, but I've read somewhere there's something else that needs to be identical? The first four digits?
Will definitely looking into this if the current setup fails, although it has been working great and tested over a week now.
Updated all firmware from all devices.
Let's wait and see how and if it develops in the next few hours.
Fingers crossed! 
After having it tested for several months I can now confirm it's running the way I wanted:
Multi 1 (connected to Cerbo); I use the virtual switch to avoid 'grid' (2nd multi) unless loads are higher than set.
I can now use their potential AND be able to charge the battery automatically (2nd Multi connected to grid) by SOC when needed in case of no sun.
No more funny readings and no more fans running when there was no load anyway.
I love the sun/summer but in this case I can't wait for the winter haha.
