Anyone had grief with a Victron SmartSolar 100/30 not bulk charging properly in winter?

Got a 200W panel (Renogy mono, Voc 24.3V) on a 100Ah AGM and the controller keeps sitting in float at around 13.2V most of the day even when the battery's only showing 60-70% SOC on the BMV-712. Absorption target is set to 14.7V, bulk done voltage is at 14.6V — all looks right on paper but it's just not doing what I'd expect.

Wondering if it's a temperature thing — it's been around 3-5°C here in the van the last few weeks and I've got the temp sensor attached to the battery. Could the compensation be pulling the voltage targets down so aggressively that it's basically skipping bulk? I've read the Victron docs but they're a bit vague on exactly how far the temp comp shifts things.

Has anyone actually cracked this or is it a known quirk with AGMs in cold weather? Happy to share screenshots from the VictronConnect app if that helps anyone diagnose it.

@HalfAJob93 classic winter absorption skip — your panel's generating barely enough current to satisfy the tail current threshold, so the controller thinks absorption is "done" and drops to float prematurely.

A few things worth checking:

• Tail current setting in VictronConnect — default is often 2A or 1% of battery capacity. Drop it to 0.5A for winter
• Max absorption time — set a fixed value rather than adaptive, something like 4–6 hours
• Battery temperature compensation — without a Smart Battery Sense or temp sensor, the controller assumes 25°C and your absorption target voltage is likely too low for a cold AGM in winter

On my narrowboat setup I run a Smart Battery Sense alongside the SmartSolar and the difference in winter bulk/absorption behaviour was immediately noticeable. Worth the £30 outlay.

What absorption voltage is currently configured?

@HalfAJob93 worth checking your absorption voltage setting and tail current threshold in the VictronConnect app. If tail current is set too high (factory default is often 2A), the controller thinks the battery's full and drops to float prematurely — happens constantly on my boat in winter when panel output is already marginal.

Also double-check your battery temperature. AGMs want higher absorption voltage in the cold (around 14.7-14.8V at 10°C vs 14.4V in summer). If you've got no temp sensor fitted, the MPPT is just guessing.

Grab the VE.Smart Networking dongle or a Smart Battery Sense — transformed my winter charging. The BMV-712 can feed temp and voltage data directly to the SmartSolar and it'll compensate automatically.

@HalfAJob93 had almost identical grief on my narrowboat last January. One thing nobody's mentioned yet — have you checked whether your panel's actually reaching the bulk voltage trigger in the first place? On cold overcast days my 100/30 was reading a deceptively healthy panel voltage on open circuit, but the operating voltage was collapsing the moment any load came on.

Worth pulling up the History tab in VictronConnect and checking your peak wattage figures for recent days. If you're consistently seeing under 40-50W from a 200W panel, the controller's barely getting started before it decides bulk is "done."

Also — what's your battery temperature? AGMs want higher absorption voltage in the cold, so if you haven't got a temperature sensor fitted that could be compounding things.

@HalfAJob93 on my narrowboat I just slap a bit of insulation round the battery — AGMs hate the cold and a chilly bank reads falsely high voltage to the controller, so it thinks it's done when it's barely started, basically the solar equivalent of your mate saying he's "nearly ready" then taking another 45 minutes.