Anyone else running EV charging off solar in a shepherd's hut setup?

Finally got my Victron Multiplus-II 48/3000 talking nicely to the Zappi via OpenEVSE mod — took three weekends and one very patient YouTube rabbit hole, but we're here.

Running 4x 200W Renogy panels on the hut roof feeding a Fogstar 48V 200Ah LiFePO4 bank. On a decent day I'm squeezing about 6–8 miles of range into the van before the battery drops below 80% SoC, which is enough for my lane since I'm not commuting to London from a field.

The garden office next door is also on the same system and somehow still works, which frankly feels like a miracle given how much the kettle hates sharing.

Anyone else managed EV charging without a grid connection, or am I the only one doing something this daft in a paddock?

JohnShaw86 | 47 posts

@DalesOffGrid nice one, that Multiplus-II / Zappi combination is something I've been eyeing up for our setup in the Pennines. Three weekends sounds about right for anything involving OpenEVSE honestly 😅

Quick question — how are you handling the prioritisation when battery SOC drops on cloudy days? I'm wondering whether you've set grid-tie assist thresholds in VEConfig or letting the Zappi's eco mode do the heavy lifting on that side.

We're currently just running a basic 48V LiFePO4 bank with a bog-standard EVSE and the manual juggling gets old fast. Would love to automate it properly before winter sets in properly up here.

What panels are you running alongside those Renogy 200Ws? Curious whether you're mixing strings.

BurnJim | 203 posts

@DalesOffGrid cracking result mate, three weekends sounds about right for getting those two to shake hands properly!

One thing worth keeping an eye on — with only 800W of panels feeding a 48V system, you'll want to make sure your Zappi's minimum charge current (6A = roughly 1.4kW) isn't constantly fighting your battery SOC on cloudy days. Might be worth setting a lower battery floor threshold in VenusOS so it doesn't try to push charge sessions when you're already drawing the bank down.

What battery capacity are you running behind that Multiplus? Makes a big difference to whether overnight top-ups are realistic or whether you're purely daytime-dependent for the EV side of things.

@JohnShaw86 the combo does work well once it's sorted — the OpenEVSE firmware approach is the sensible route these days.

Wendy1968 | 312 posts

@DalesOffGrid brilliant work getting that sorted! I've got a slightly different setup — Multiplus-II 24/3000 with a Tesla Model 3 and we charge mostly overnight using stored solar from the previous day. One thing I'd flag: keep a close eye on your battery state of charge thresholds in VE.Configure, especially through autumn. I was too aggressive with mine and ended up underselling the batteries on a run of overcast days in October.

What battery bank are you running with those Reno panels? I'm on 200Ah of lithium and honestly I'd go bigger if I were starting again — EV charging really does gobble capacity faster than you expect even at low amps.

@JohnShaw86 the Zappi integration is genuinely worth the faff once it's dialled in.

Got a similar bodge running at my cabin — Multiplus-II 24/3000 rather than the 48V, which I slightly regret now. Charging a small EV off solar feels almost too good to be true the first time it actually works properly.

One thing worth flagging: if you're not already, set a minimum SOC before the Zappi pulls anything. Learned that the hard way after a cloudy week left me with basically nothing in the Fogstar cells.

Also curious what your Zappi's minimum charge current is set to — the 6A floor can be awkward with marginal solar. Some people drop it further with the OpenEVSE firmware but I've not gone down that rabbit hole yet.