Anyone know if a Victron SmartSolar 100/30 will work with lithium without the temp sensor?

Got a bit of a head-scratcher here and hoping someone can save me from going down another rabbit hole.

Running a SmartSolar 100/30 on my static caravan setup — currently charging a pair of 100Ah lead-acids but I'm planning to swap over to a Fogstar Drift 100Ah lithium sometime in the spring. The old batteries are on their last legs, frankly.

Now, I know with lead-acid the temp sensor earns its keep, especially through winter. But with lithium it's a different story isn't it? My understanding is that most decent LiFePO4 batteries have their own BMS handling temperature cutoff, so the Victron doesn't need to know the ambient temp to protect the cells — the battery sorts itself out.

What I'm less sure about is:

• Will the 100/30 throw any warnings or behave oddly without the sensor connected when set to lithium profile?
• Should I be using the Li preset in VictronConnect or setting a custom absorption/float voltage manually?

I've had a poke around the Victron docs and they're not exactly written for people who've had three cups of tea and still can't concentrate properly, so I may have missed something obvious.

The caravan is in North Yorkshire if that's relevant — temperatures can get properly grim up there from October onwards, which is partly why I'm fussing about this.

Anyone done a similar swap? Did you bother with the temp sensor or just leave it off entirely?

@RetiredEngineer72 running mine without the temp sensor on a Fogstar Drift 100Ah in the van — the SmartSolar handles it fine because most lithium BMS units already have their own thermal protection built in.

The key thing is making sure your charge profile is set correctly in the VictronConnect app. I've got mine on the User Defined lithium preset rather than the generic lithium option, which lets you dial in the exact voltages your battery manufacturer recommends.

The temp sensor matters more for lead-acid because the charge voltage needs compensating with temperature swings. Lithium is far less fussy about that.

Only caveat — if your static is somewhere that gets genuinely cold in winter (sub 5°C), worth checking your BMS will cut charging before the cells get damaged rather than relying on the MPPT to do it.

@RetiredEngineer72 the good news is lithium basically is its own temperature compensation — it just says "charge me properly or I'll sulk." 😄

The SmartSolar's fixed lithium profile works fine without the temp sensor because a decent LiFePO4 BMS will disconnect before anything goes pear-shaped anyway. That's

@RetiredEngineer72 here's the bit nobody's mentioned yet — the temp sensor on the SmartSolar is designed for lead acid compensation (adjusting voltage based on temperature). LiFePO4 doesn't want that voltage fiddling at all, which is actually another reason to leave it disconnected.

What you do want is a BMS with its own low-temp charge protection. Most decent cells — Fogstar, Eve, CATL-based packs — will handle that internally and just disconnect if it's dangerously cold.

The critical step is setting a lithium charge profile manually in VictronConnect. Fixed absorption voltage around 14.2V, no float (or float at 13.5V), absorption time as short as possible. That's where people go wrong — they assume "no temp sensor = sorted" but leave the charger on an AGM profile. That's the actual rabbit hole worth avoiding.

Good shout from @LiFePO4Nerd there — worth adding that if your Fogstar or whatever LiFePO4 you go with has a built-in BMS (they all do these days), that's your real protection layer. The BMS will just disconnect if temps go daft, simple as.

Main thing is making sure your charge profile in VictronConnect is set to lithium properly — default lead acid settings will overcharge it. Easy to miss if you're coming from lead.

Had mine running on a Fogstar Drift for about 18 months, no temp sensor, no drama. Static setup like yours is probably even less of a concern than a van bouncing around in all weathers.

So what actually happens if it gets genuinely cold — below 5°C say — and the BMS cuts charging to protect the cells? Does the SmartSolar just sit there confused, or does it throw a fault? My static's in Scotland so this isn't a hypothetical.

Also nobody's mentioned whether the charge profile matters more than the sensor here. I've got mine currently set to AGM because I've not switched the batteries yet. Do I need to sort a proper lithium preset before I connect the new cells, or can I get away with flicking it over in the VictronConnect app after the fact?

Asking because I nearly fried a Renogy controller years back by connecting first and configuring second. Don't fancy repeating that with kit that costs actual money.