Orion XS reverse charging: feature request PV starter battery charging

Really glad Victron pushed the reverse charging feature out via firmware — that kind of update after purchase is what keeps me loyal to the brand tbh.

Got me thinking though. On my narrowboat I've got a Cerbo GX managing everything, and the Orion XS is doing a solid job keeping the starter battery topped up from the leisure bank. But what I'd love to see next is some way to route excess PV into the starter battery when it's sitting low and the alternator isn't running.

At the moment my setup means the starter battery is basically ignored by solar — it just waits for engine time. On longer winter mooring periods that's a bit rubbish, especially if I've had to use the starter battery for anything.

Wondering if this is even feasible within the Orion XS architecture or whether it'd need a separate DC-DC path entirely. Anyone run a relay-based workaround through VenusOS? I've seen some custom scripts floating about but nothing that felt properly integrated.

Would also be curious if this is relevant to anyone running motorhome setups — seems like the use case is similar, lots of solar on the roof but the starter battery only charges on the move.

Is there any way to submit this as a feature request to Victron directly, or does it have to go through the community portal? Last time I tried navigating that it wasn't exactly intuitive.

@SolarJulie the dream is real — PV → Orion XS → starter battery would basically mean my shepherd's hut roof is doing the work my alternator used to beg for 😂

Victron could potentially gate it off a BMS signal so it only tops the starter when the house bank's already fat and happy — like a pecking order built into firmware rather than bodged relay logic.

Fogstar drift lithiums as house bank already handle priority charging beautifully in my setup, so the logic exists upstream, just needs exposing downstream through the Orion.

Stick it on the Victron Community feature request board — they actually read those, unlike certain other manufacturers whose suggestion box is clearly a shredder.

@OffGridHamish that's exactly the use case I've been mulling over for my cabin setup too. At the moment I'm running a separate small Renogy controller just to keep the starter battery ticked over, which feels like an unnecessary extra box on the wall.

If Victron could implement PV-source logic in the Orion XS firmware — essentially letting it pull from a PV bus rather than just the house bank — that would genuinely simplify so many installs. One device doing the DC-DC and the solar top-up work.

Has anyone raised this formally on the Victron Community forum? I'd happily upvote it. Worth getting enough voices behind it before Victron's dev team prioritise other things.

Does the feature request need to account for MPPT behaviour, or would it just treat PV input as a voltage source the same way it handles the house bank?

This is basically what a lot of us want — a "solar donation" mode where excess house bank charge gets pushed to the starter rather than wasting it.

Worth noting the Orion XS already knows the input voltage pretty accurately, so in theory the firmware logic is already halfway there. The missing piece is probably the charge profile management for the starter battery side.

Workaround I'm running on my garden office setup: separate small Renogy 20A MPPT dedicated solely to the starter/chassis battery. Crude but effective, and means the starter stays healthy without touching the house bank logic at all.

For the narrowboat use case @SolarJulie is describing, that might actually be simpler than waiting for Victron to implement it — starter batteries on boats are usually tucked somewhere a second controller cable could reach easily enough.

@CE_Builds "solar donation mode" is a great way to put it actually. My garden office setup has a similar logic problem — the leisure bank sits fat and happy on sunny days whilst the van starter battery quietly sulks.

What I'd love to see is a voltage threshold trigger rather than just time-based — so the Orion XS only reverses into the starter once the house bank clears, say, 27.2V (on 24V). Means you're genuinely donating surplus rather than robbing Peter to pay Paul during a grey week.

Victron's Connect ecosystem already has the building blocks for conditional logic like this. Feels like it wants to exist as a GX automation rule if nothing else — even if the Orion XS firmware itself doesn't carry it natively.