Help with SPD recommendation. (Other suggestions or tips welcome too!)

Been doing a fair bit of research into surge protection devices lately after finally committing to a proper solar upgrade on the Vivaro — 400W of panels feeding a Victron SmartSolar MPPT into a pair of Fogstar Drift 100Ah LiFePO4s. The system's been solid but I've been increasingly paranoid about transient voltage spikes, particularly when the compressor on my 12V diesel heater kicks in and out.

For anyone running LiFePO4 chemistry specifically, my understanding is that the BMS offers some inherent protection, but it's not designed to handle repeated transient events — that's wear you don't see until it's too late.

What I've been looking at:

• DC-side SPD rated to 12/24V (harder to find than AC equivalents)
• Victron's own surge arrestors, though they're priced accordingly
• Some folk on other forums swear by automotive-grade MOV-based suppressors wired in parallel close to the battery terminals

One thing I haven't fully resolved is where exactly to position the SPD in the chain — pre or post the MPPT? My instinct says post, protecting the load side, but the panels themselves are arguably the bigger lightning/surge risk in a roof-mounted setup.

Anyone here running SPDs in a motorhome or van setup? Particularly interested if you've got experience with:

1. DC SPDs at lower voltages (not just 48V grid-tied stuff)
2. Whether it's worth protecting both the panel input and the load output
3. Any UK suppliers worth recommending beyond the usual Amazon lottery

Would be good to get some real-world input rather than just spec sheets — the documentation for a lot of this kit assumes a static installation rather than

Hey @VivaroAdventure, nice setup! For a van install at that scale I'd point you towards the Citel DS50VGP or similar Type 2 SPD on the DC side — rated for the voltage range you'll likely be running. Make sure you're matching the SPD's Uc rating to your actual open-circuit panel voltage with a decent safety margin.

One thing people often overlook on van builds specifically — bond your SPD as physically close to the MPPT as practical, and keep those earth leads short. Long earths largely defeat the purpose.

Also worth grabbing a DIN rail mounted unit if you're running a proper enclosure, makes everything much tidier and replaceable down the line.

What's your array voltage running at? That'll help narrow down the spec further. 🙂

Just don't forget your SPD is only as good as the earth bonding holding it all together — learned that the expensive way when my garden office Victron setup basically shrugged at a nearby lightning strike like "not my problem mate" 🔌⚡

Good shout from @MrBodge73 on the earthing — can't stress that enough.

One thing nobody's mentioned yet: fuse your SPD line separately. Had a shepherd's hut build where the SPD itself failed short and took out more than it should've because it was sharing protection with everything else. Lesson learned.

Also worth thinking about Type 1+2 combined units if you're regularly parking in exposed spots — Type 2 alone is fine for most van life but if you're out on moorland or highlands regularly the combined units aren't much dearer and give better indirect strike protection.

For a Victron-based setup specifically, check Victron's own guidance on SPD placement relative to the MPPT — they're quite particular about it and getting it wrong can void warranty claims.

Good point from @MrBodge73 and @TracyKnight on earthing — won't repeat it, but it's critical.

One thing worth clarifying though: SPD type matters more than brand. For a van/mobile application you technically want a Type 2 (or combined Type 1+2) device. Type 3 alone isn't sufficient as first-line protection.

Also — your SPD needs to be rated for your actual system voltage. DC-side and AC-side are completely different devices; don't mix them up. I've seen people fit an AC SPD on their DC bus. Doesn't end well.

On the DC side for a 12V system, something like the Citel MDS50-12 is properly rated. Victron also sell their own SPDs now if you want everything from one ecosystem.

Check the Imax discharge current rating too — higher is better for exposed roof-mounted panels.