New Smartsolar MPPT 100/50 not charging

Had something similar with my 100/30 a while back — new out of the box and barely a flicker on the charge side.

Turned out I'd wired the panels in series without double-checking the Voc first. In cold weather that can spike well above what you'd expect, and if the controller sees something it doesn't like on startup it just... sits there doing nothing useful. Worth checking your actual open-circuit voltage with a multimeter before anything else.

Also — and this catches people out — the Smartsolar won't start charging until it sees a minimum panel voltage above the battery voltage. If your battery's already fairly full or the panels are shaded, it'll just show absorption or float with zero amps. Looks broken, isn't.

Few things worth checking:

• VictronConnect app — connect via Bluetooth and look at what the controller is actually reporting. Faults show up there clearly.
• Battery voltage at the controller terminals, not just at the battery. Voltage drop on dodgy connections is surprisingly common.
• PV input voltage — if it's reading 0V something's wrong upstream of the controller.

What's your battery setup? 12V or 24V matters quite a bit here — if you've got two 12V panels in series feeding a 12V bank, the voltage could be tripping an overvoltage protection internally depending on conditions.

Not saying that's definitely it but it's worth ruling out before assuming the unit's faulty.

Anyone else seen odd startup behaviour with the newer Smartsolar firmware? Noticed mine got a bit temperamental after one of the updates last year.

@Wez1961 did you check whether the MPPT had gone into a protection mode? I had a similar head-scratcher on my boat — turned out the unit had latched into a fault state and needed a full power cycle (disconnect battery first, then panels) to clear it.

Also worth checking: is the battery voltage being read correctly in the VictronConnect app? If the MPPT thinks the battery is already full it simply won't charge. What voltage is it actually showing on the battery terminals vs what the app reports?

@Wez1961 there's another one worth ruling out — the battery voltage sense. My first Victron install in the shepherd's hut had me stumped for a full afternoon. The MPPT was seeing a falsely high battery voltage because I'd tapped the sense wires too close to the charge input rather than directly at the battery terminals. Controller thought the bank was full, sat there doing absolutely nothing.

Worth pulling up the history tab in the VictronConnect app too — it'll show you bulk/absorption cycles even if current charging looks flat. Sometimes the unit has been working, just not in the way you're watching for.

@Wez1961 worth checking the absorption/float voltage settings too — if someone's previously set the charger profile to something like 14.4V absorption but your battery BMS is cutting out at 14.2V, the MPPT just sits there looking confused.

Also check VictronConnect actually shows the input voltage from the panels when you tap on the device. If PV voltage is showing 0V or something stupid like 2V, you've likely got a dodgy MC4 connection or a dry joint on the panel combiner box. Seen this a few times.

Easy test: disconnect everything, multimeter on the panel output terminals in direct sun — if you're not seeing expected Voc there's your culprit before the MPPT even comes into play.

@Wez1961 one thing nobody's mentioned yet — check your BMS comms if you're running lithium. Had this exact nonsense on my narrowboat last spring with a Fogstar Drift 200Ah. The MPPT was sat there looking perfectly happy in Victron Connect, showing bulk charge, but the BMS had quietly sent a charge inhibit signal via the VE.Direct port and current was effectively zero. Took me two hours of increasingly colourful language to figure it out. If you're on lead-acid ignore me, but if you've got any smart battery in the system, disconnect the data cable temporarily and see if the controller actually starts pushing amps. Sometimes the solution is stupidly simple and that's what makes it so infuriating.

Also double-check the battery + connection at the MPPT itself — mine looked seated but was barely making contact, spent a whole Saturday convinced my Fogstar cells were dying before I noticed the terminal was just finger-tight 🔩