Anyone else running a split-charge relay alongside solar on a tight budget? How are you managing the two together?

I've been piecing together a fairly basic system in my Transit camper over the past few months — 200W of cheap panels off eBay, a Victron 75/15 MPPT, and a 110Ah leisure battery. It's been decent enough for keeping the lights and phone charging ticking over, but I'm struggling a bit during the winter with just solar. Parked up for a few days of proper grey British weather and the battery is looking sorry for itself by day two.

So I'm thinking about adding a split-charge relay off the alternator to top things up on driving days. I've seen the basic VSR (voltage sensitive relay) kits on Amazon for around £15-£25 and I'm wondering if that's genuinely good enough, or whether I'd be throwing money away and should save up for a proper DC-DC charger like the Victron Orion. The Orion seems to be what everyone recommends but it's £80-£100 for the non-isolated version, which is a stretch right now.

Has anyone here got a VSR running alongside an MPPT without any issues, or is it genuinely a problem worth spending the extra on? My van is a 2014 Transit so it's got the smart alternator setup — not sure if that changes things significantly.

RetiredNurse43 | 847 posts | ⭐ Trusted Member

@WillRoss That sounds very similar to how I started out! I've got a split-charge relay on my old Berlingo alongside a modest solar setup and they work together surprisingly well without much fuss. The main thing I'd flag is keeping an eye on your battery not getting confused between the two charging sources — in practice it's rarely an issue but worth monitoring voltage with a simple battery monitor. I picked up a Victron BMV-712 secondhand which transformed how I understood what was actually happening. On overcast days here in Scotland the relay does most of the heavy lifting anyway! What's your alternator output like? Some older Transits have fairly modest charging capacity and it's worth knowing your baseline before you start tweaking anything. 😊

LisaHunt88 | 203 posts | 🌱 Member

Running almost identical on my static caravan — 200W Renogy panel with a Victron 75/15 and a split-charge from the site car park hook-up when I bother driving over.

The thing I'd add that nobody mentions: watch your battery voltage carefully when both sources are active simultaneously. My MPPT and the split-charge were occasionally fighting each other and I was getting weird absorption cycling. Fixed it by adding a basic battery-to-battery charger (B2B) instead of a dumb relay — proper current limiting means the two sources play nicely together.

Fogstar Drift 100Ah LiFePO4 helped massively too since it accepts charge from both without complaining, unlike my old AGM which seemed to sulk constantly.

Not saying you need to spend big, but a smart relay or B2B is worth saving up for if you're running dual sources regularly.

StormyMechanic | 1,204 posts | ⭐ Trusted Member

The thing that caught me out early on — and nobody warned me — was the split-charge relay dumping alternator voltage straight into batteries that were already near full from a sunny afternoon. My Victron MPPT had done its job beautifully, then the relay piled in and confused everything.

What sorted it for me at the cabin was wiring a simple voltage-sensing relay set to not engage above around 13.6V. Costs pennies compared to a proper DC-DC charger. The relay only kicks in when the bank actually needs it — usually early morning before the panels wake up.

Not the slickest solution, @WillRoss, but on a tight budget it keeps the two sources from fighting each other without spending £150+ on a Victron Orion.