Brand new Multiplus 2 not powering up

Had something similar happen with my Victron Multiplus-II 48/3000 when I first installed it last year — genuinely concerning when you've just dropped that kind of money and get absolutely nothing.

A few things worth checking straight away:

• Pre-charge resistor — did you use one when connecting the battery bank? Without it, the capacitors inside the inverter can cause issues on first connect, and some units can appear dead afterwards
• Fuse on the DC side — sounds obvious but worth pulling and checking visually, even brand new fuses can fail
• Battery voltage at the inverter terminals themselves — not just at the battery. Voltage drop across dodgy connections or undersized cable can fool you
• The rocker switch on the unit — easy to miss, especially if you're rushing the install

What battery setup are you running with the 24/5000? I ask because with a 24V system you need a fairly beefy bank to give the inverter what it needs on startup. If the BMS on a lithium pack is tripping due to inrush, you'd get exactly this symptom — no signs of life, unit appears totally dead.

Also worth checking whether Victron has had any recent firmware issues on that model. The community forum on their own site sometimes flags batch-specific problems before the official docs catch up.

What does your DC wiring setup look like — busbars, fuse size, cable gauge? That'd help narrow it down. Others on here have had what seemed like dead units that turned out to be installation gremlins rather than faulty hardware.

@Mike1980 what ended up being the cause in your case?

Mine did something similar when I first wired it up in the static van — turned out I'd not torqued the DC terminals properly and it just… refused to do anything. No lights, no fan, nothing. Felt like a brick.

Few things worth checking if nobody's mentioned yet:

• Is the battery voltage actually at the terminals on the Multiplus, or just at the battery? Voltage drop across dodgy connections can fool you
• What's your BMS doing — is it allowing discharge?
• Have you tried the on/off switch on the unit itself rather than just the remote panel?

What battery setup are you running? That changes the diagnosis quite a bit.

@Mike1980 @SmartSolarNerd — worth methodically ruling out the basics before assuming a fault:

1. DC fuse/breaker between battery and Multiplus — is it rated correctly and actually closed? The 48/3000 needs a properly sized MEGA fuse
2. Cable gauge — undersized DC cables cause a voltage drop that prevents startup
3. Battery voltage — what's the resting voltage at the Multiplus terminals under load, not just at the battery

In my static caravan setup I had a similar "dead on arrival" panic that turned out to be a 48V lithium pack with BMS protection tripped. The Multiplus draws a brief inrush on startup that can trigger an undersized BMS.

Also check the VE.Bus or remote on/off terminals — some installs accidentally leave the remote control connector in the off position. Easy to miss.

What's your battery chemistry and BMS brand?

@BlownFuse good shout on the basics — I'd add one thing that caught me out with my own Multiplus-II setup: the remote on/off connector (the two-pin plug on the unit itself).

Mine came with that unpopulated and the unit just sat there doing nothing. Bridging pins 1 and 2 with a small jumper sorted it immediately. Felt like an idiot but it's not obvious from the quick-start guide.

Also worth checking the battery voltage at the unit terminals rather than at the battery — I had enough voltage drop across undersized cable to confuse things initially.

Great point from @LiFePO4Fan on the remote on/off — that connector is a silent killer of first installs.

One thing nobody's mentioned yet: the Multiplus-II has a minimum voltage threshold before it'll even attempt to boot. If your 48V bank is freshly built and cells aren't balanced or top-charged, you might be sitting at 44-45V and the unit just refuses to play ball. Completely normal behaviour, completely terrifying if you don't know about it.

Also worth connecting via VE.Bus to VictronConnect — even a non-booting unit will sometimes enumerate enough to throw error codes that tell you exactly what it's sulking about.

Had this exact scenario with my cabin setup. Spent 45 minutes convinced I'd bought a brick, turned out my Fogstar cells had shipped at storage voltage. One bulk charge cycle later, she fired up perfectly.

Had exactly this with my garden office install — spent a genuinely embarrassing amount of time staring at it before realising the battery voltage was the culprit. The Multiplus-II has undervoltage lockout and if your pack is sitting low after storage or shipping, it simply won't budge. Worth sticking a multimeter directly on the DC terminals at the unit itself (not just at the battery) to rule out volt-drop across undersized cable or a dodgy lug connection. I was running 16mm² initially which was marginal and caused enough drop under load to confuse things. Also double-check your VE.Bus comms aren't interfering if you've got a Cerbo or anything else connected — sometimes disconnecting everything and doing a bare-bones power-up test isolates the issue quickly.

Right, so @AndyRobinson's embarrassing stare-off with the unit — I know that feeling intimately. Mine on the narrowboat nearly ended with me chucking it into the canal.

One thing nobody's mentioned yet: check your DC fuse or breaker between the batteries and the Multiplus-II is actually rated correctly AND fully seated. A partially-tripped breaker will read as "on" but pass zero current. Caught me out completely.

Also worth grabbing the VictronConnect app via Bluetooth — even a seemingly dead unit often responds enough to throw a fault code. Saved me hours of guesswork on the boat.

If you're on 48V, double-check your battery bank voltage with a multimeter at the inverter terminals, not at the batteries. Voltage drop across dodgy connections can fool the low-voltage cutoff into thinking the bank is dead.