Smart MPPT 100/20 ne produit pas

Had a similar headache with my Victron Smart MPPT 100/20 a while back in the shepherd's hut build — solar input looked fine in the VictronConnect app but the thing just wasn't pushing any meaningful charge into the batteries. Drove me mad for days.

Turned out it was a combination of things:

• Battery voltage sense was off because I hadn't set the correct battery type (had it on AGM, switched to lithium when I fitted the Fogstar Drift 100Ah)
• The absorption voltage was set too low, so it was basically calling it done before it had really started
• Also had a dodgy MC4 connector on one of the panel strings — losing voltage before it even got to the controller

Worth checking in VictronConnect > History tab — if you're seeing zero yield on days you know were sunny, that's usually a clue something upstream is wrong rather than the MPPT itself being faulty.

Also — is your BMS cutting out? If you're running lithium and the BMS is briefly disconnecting under load or during a voltage spike, the MPPT can go into a weird protective state and just... stop. Seen it happen with cheaper BMS units.

Anyone else had the MPPT seemingly just "give up" mid-day for no obvious reason? Curious whether this is more common than people realise — especially on smaller hut/tiny house setups where the wiring runs are short but the connectors get a lot of vibration and movement.

Happy to share my wiring layout if it helps anyone diagnose.

@JLB_Boats the thread title's in French so just checking — are you getting the "absorption" phase triggering too early? Classic symptom when the battery voltage is being read slightly high (loose connection causing a voltage drop that fools the MPPT into thinking it's fuller than it is).

On my van setup I had exactly this — Victron Smart MPPT 100/20 sitting there looking busy in the app but actual amps into the Fogstar Drift LiFePO4 were pathetic. Turned out to be a dodgy negative connection at the busbar.

Worth checking:

• All terminal torque values (people forget the battery side)
• Whether your battery temp sensor is positioned correctly
• That the MPPT firmware is current via VictronConnect

What's your battery chemistry? LiFePO4 absorption thresholds are completely different to AGM and the default profile can catch people out.

@JLB_Boats classic one this. Nine times out of ten when the MPPT looks fine but isn't pushing decent amps, it's a voltage sensing issue — the controller thinks the battery is fuller than it actually is, so it backs off early.

Check your wiring resistance between the MPPT and battery. Even a small voltage drop on the battery positive/negative leads fools the unit into premature absorption. Victron recommend keeping that run as short as possible.

Also worth checking in VictronConnect: History > Max charge current. If that's suspiciously low, you've found your culprit. Had exactly this on my boat build — turned out to be a loose terminal on the negative bus causing phantom voltage readings. Tightened everything up and it sorted itself immediately.

What battery chemistry are you running? LiFePO4 with a BMS can also cause apparent throttling if the BMS is communicating oddly.

@RayWatson81 makes a fair point about voltage — worth elaborating though: on my narrowboat setup I had the exact same symptom and it turned out the battery voltage sense was reading high due to a dodgy connection at the battery terminals, so the MPPT thought the bank was fuller than it was and throttled output accordingly.

Check your wiring end-to-end with a multimeter. Voltage at the MPPT battery terminals versus actual battery terminal voltage — any meaningful discrepancy there tells you something. Also worth pulling the history data in VictronConnect; if your max charge current is suspiciously low across multiple days, that points toward a sense issue rather than a shading or PV problem.

What battery chemistry are you running? Charge profile settings on AGM versus LiFePO4 can cause exactly this kind of quietly-wrong behaviour.

Hey @JLB_Boats — one thing nobody's mentioned yet: check your battery temperature compensation settings if you're running a lithium. The 100/20 defaults to a lead-acid charge profile, and if VictronConnect isn't configured correctly for your battery chemistry, it'll throttle back way sooner than it should. Looks perfectly healthy in the app but you're barely getting any real charge through. Also worth a quick check on whether your absorption voltage ceiling matches what your BMS actually wants — mismatches there can cause the controller to back off thinking the battery's nearly full when it isn't. Happened on my shed build last winter and drove me mad for a fortnight! 😅