Anyone else running a Victron Orion-Tr Smart alongside a DC-coupled solar setup — how are you handling the charge priority?

Got a bit of a head-scratcher here. Running a 200Ah Fogstar Drift LiFePO4 on a 12V system in my tiny house build, with 400W of solar through a Victron SmartSolar 100/30. Recently added an Orion-Tr Smart 12-12/30 to top up from my van's alternator when solar's been rubbish (which, you know... winter in the UK).

Problem is I'm not entirely sure how the two play together when both are active simultaneously. Both are on VE.Smart networking via Bluetooth. In theory they should both be seeing the battery voltage and cooperating, but I've had a couple of instances where the Orion seemed to be pushing current in while the MPPT was also in bulk — battery hit absorption voltage faster than expected and I'm wondering if something's logging wrong or if there's actually a calculation issue somewhere.

Has anyone actually stress-tested this dual-input scenario with a Fogstar or similar 100A BMS battery? Curious whether the BMS is doing any of the heavy lifting here or if I should be relying entirely on the Victron network to sort charge coordination.

Hey @LiFePO4Fan, great setup! One thing worth considering is using the Orion's engine detection feature properly so it's not fighting your SmartSolar when both are trying to bulk charge simultaneously. I've got a similar arrangement and what worked for me was setting the Orion to a slightly lower absorption voltage than the SmartSolar — let the solar do the heavy lifting when there's decent irradiance, and treat the Orion more as a top-up from the alternator when you're moving or the sun's being typically British about showing up.

Also make sure you've got both devices visible in VictronConnect and check your charge profile settings match across both — Fogstar publish recommended charge parameters on their site which is handy. What's your current absorption and float voltage set to on each?

@LiFePO4Fan ooh this is almost exactly my setup except I've got it all going into a garden office rather than a tiny house. One thing I kept banging my head against — have you looked at the charge source priority settings in VictronConnect? You can essentially tell the Orion-Tr to throttle back when the SmartSolar is already pushing decent amps, but I'm honestly not 100% sure I've configured mine optimally either.

What's your absorption voltage set to on both devices? I had mine slightly mismatched for ages without realising and the Fogstar was getting confused about when to taper off.

Are you using a Cerbo GX or anything to tie it all together? I keep meaning to add one but haven't justified the cost yet. Would make diagnosing this so much easier presumably?

@LiFePO4Fan nice one, the Fogstar Drift is a solid choice for that kind of build. One thing I'd look at is setting your SmartSolar's absorption voltage slightly higher than the Orion's — so on a good solar day the MPPT essentially "wins" and the Orion backs off naturally once the battery's happy. With VE.Smart networking you can get both talking to each other via Bluetooth which helps enormously with coordinated charging. Also worth enabling the Orion's input voltage lockout properly so it's not pulling from your alternator when the engine's just ticking over — saves a lot of grief with smaller alternators. What voltage thresholds are you currently running on both units? Knowing your bulk/absorption/float settings would help narrow down whether you're likely to see them fighting each other.

Been through exactly this rabbit hole on my boat build. The thing that sorted it for me was using VE.Smart Networking to link the SmartSolar and the Orion together — once they're sharing battery voltage and temperature data on the same network, the Orion naturally backs off when solar is doing the heavy lifting.

The key bit people miss: set your Orion's absorption voltage slightly lower than the SmartSolar's. Maybe 5-10mV lower. That way solar always "wins" the top-of-charge conversation and the Orion isn't fighting it unnecessarily.

@SolarMike makes a fair point about charge settings generally, but the VE.Smart piece really is the glue that makes the whole DC-coupled setup behave as one system rather than two chargers arguing over the same battery.

Just to add to what @VDH_Boats mentioned about VE.Smart Networking — once you've got that set up, the SmartSolar naturally takes priority because the Orion-Tr will back off when it sees the battery voltage climbing from solar input. Works a treat in practice.

One thing worth double-checking is your absorption voltage settings are identical across both devices. If they're even slightly mismatched you can end up with one charger fighting the other, which is particularly unforgiving on LiFePO4 chemistry. I'd set both to 14.2V absorption and 13.5V float if you're running standard Fogstar Drift parameters — matches their own recommendations nicely.

Also, are you running the Orion in engine-running-only mode? Assuming this is connected to a vehicle alternator rather than mains?

Great points from @VDH_Boats and @Tel1997 on VE.Smart Networking — that really is the backbone of getting this working properly.

One thing nobody's mentioned yet: have a good look at your absorption voltage settings across both devices. If your Orion and SmartSolar aren't set to identical charge profiles for the Fogstar Drift, you can end up with one device "disagreeing" with the other mid-charge cycle, which causes unnecessary cycling and can confuse the BMS.

Fogstar publish recommended charge parameters on their site — worth grabbing those exact figures and inputting them consistently into both units via the VictronConnect app. I'd also suggest setting a slightly lower tail current threshold on the Orion than the SmartSolar, so solar naturally takes priority when it's doing the heavy lifting and the DC-DC steps back gracefully rather than fighting for headroom.