Victron mppt 75/15 not loading

So my Victron MPPT 75/15 has decided to go on strike mid-week, which is absolutely peak behaviour considering I've got the garden office running off it and a deadline looming.

Here's what's going on:

• Panels are showing ~19V at the terminals when I measure with my multimeter
• The VictronConnect app shows the controller is alive but charging has just... stopped
• Been like this for about 4 days now
• Fogstar 12V LiFePO4 battery is sitting at 70% from before the fault, so nothing's died yet

What I've already ruled out:

• It's not a blown fuse (checked both the PV fuse and the battery fuse)
• Wiring looks intact, no visible chafing or dodgy connections
• The app isn't throwing any obvious error flags, which somehow makes it more suspicious

My setup is in a shepherds hut so it's not exactly like I can run an extension lead from the house — this thing needs to work!

Has anyone seen the MPPT just decide to stop accepting charge like this? I'm wondering if it could be:

1. A temperature protection issue (it has been properly Baltic here lately)
2. Some kind of absorption/float quirk where it thinks the battery is full but clearly isn't
3. A dodgy PV input connection I've missed

Worth noting the panels are Renogy 200W mono if that's relevant. Any UK folks dealt with this in winter conditions specifically? Happy to pull logs from the app if that helps diagnose it.

@BoatPaddy you've cut off your post mid-sentence, which is either a dramatic cliffhanger or your battery just died — either way, tell us: what are the actual symptoms, what does the VictronConnect app say the charge state is, and have you checked that your PV open-circuit voltage isn't exceeding 75V (easy mistake with series-wired panels)?

The 75/15 is solid kit but it'll throw a #38 wiring fault or just sit there looking smug if the input voltage is out of range. Also worth confirming your battery type setting — if someone's accidentally switched it to Gel when you're running lithium, it'll undercharge like a teenager doing homework.

@BoatPaddy yeah gonna need you to finish that sentence before anyone can help properly 😄

In the meantime — classic things to check while you're getting that post finished:

• What's the battery voltage showing in the VictronConnect app?
• Any error codes on the unit (blinking LEDs)?
• Is it actually the MPPT or could it be a wiring/fuse issue upstream?

Had a similar panic in my van build once, turned out to be a blown inline fuse between the panels and the controller. Twenty minutes of stress for a 50p fix.

Download VictronConnect if you haven't already — the Bluetooth diagnostics on these units are genuinely brilliant for narrowing it down fast.

@BoatPaddy looks like the post got cut off at both ends — @OldSailor and @BurnBen already flagged it but we're still missing the actual symptoms.

When you get chance, tell us:

• What the MPPT display/LEDs are showing (bulk, absorption, float, or error codes)
• Battery voltage at the terminals
• Whether the VictronConnect app is showing anything useful
• Panel VOC vs your 75V input limit — easy to accidentally exceed it if panels are wired series

The 75/15 is generally rock solid so there's usually a logical cause. Most common culprits I've seen are reverse polarity on initial wiring, a tripped internal protection, or panels pushing too high a voltage in cold weather.

Get the VictronConnect readout if you can — it logs faults and that'll narrow it down sharpish.

Seems like the forum's eaten your post from both ends — the classic double-truncation. Genuinely curious what the issue is though because I've got a 75/15 in my van build and it's been faultless, so if yours is misbehaving I'd like to know what to watch for.

When you get a chance to repost, worth including:

• What the VictronConnect app is showing (any error codes?)
• Whether the MPPT LED is doing anything unusual (solid, blinking, what colour?)
• Panel voltage going into the controller vs what's coming out
• Whether this started suddenly or gradually crept up

The garden office angle is interesting too — is it a fixed panel setup or portable? Wondering if a connection has worked loose somewhere.