Multiplus set up sequence

I am in the final planning phase of a Victron 3000 24v Multiplus grid charge supplied system. This is Not grid tied.

I will only be feeding at 30 amp max from the grid and will be using a subpanel (separated neutral ground) for the supply side. Later it will be balanced with solar panels.

From previous discussions it was determined that this will be grounded through the grid supply line.

There has been a lot of discussion in the past about making sure that the batteries are attached before attaching the solar panel input in order to avoid "magic smoke". As stated above, the solar panels are in the future.

There has also been a lot of discussion about precharge circuits or using a resister to precharge the capacitors in order to avoid damaging sparks.

My questions are hopefully basic. Will the batteries need to be attached before attaching the ac input? If not, does the ac input precharge the capacitors?

I may have opened a can of worms. Hope not but trying to sequence this in my mind beforehand.

I believe- but I am not positive- that you can connect the 120v up first to charge up the capacitors. Then attach the DC wires. (This would be a good question for your Victron dealer).

I put a Rec pre-charge on my MotorHome- just so I didn’t have to think about it in the future. This worked for my system because my bms uses a contactor. The spark can weld contactors - so that was a concern of mine too.

When you build your system - think through the startup and shutdown procedures and write them down and post next to your system- just so you don’t forget.

Good Luck

Checked this out. Apparently the ac does not pre charge the capacitors.

If in doubt, simply fit a pre- charge circuit, consisting of a push switch and a resistor - fuse accordingly as circuit/ parts of it will be live at all times. Or use a resistor to bypass main DC isolator to pre-charge.
Victron state "Be aware there may be a spark when making battery connections ", but give no other info in the inverter manual I've looked at.

I wired my batteries to the inverter first, with the battery circuit breakers turned off and the inverter power switch turned off. Then I turned the battery circuit breakers on, and then I turned the multiplus II power switch on. I'm using a 48V model with 2xlifepower4 48V 100AH.

I verified the output frequency and voltage of the ac output terminals before connecting it to my main panel (I am off-grid).

If you want to be able to use a "precharge resistor" the first time you touch your inverter terminals with a hot wire (because you have no battery cut off switch, or fuse to remove from its' holder, for example), you could make the contact using a pencil that has been sharpened at both ends, that is a resistor. Or buy a resistor just for that purpose.

EDIT: After you've wired the batteries, here's the best reference in existence for wiring its' AC terminals:

Good tips in video in regards leaving slack, how annoying is it when you go to replace something and who ever done it didnt leave a bit of slack and the new items terminals are just a bit further away ☹.
Disappointed that no earth sleeve was put on the bare earth wire though.