Victron Orion stuck in Absorption Mode

Mine did exactly this last winter — Fogstar Drift 100Ah sitting there getting cooked in absorption for four hours while I wondered why my van smelled like a chemistry lesson.

Turned out the Orion-Tr Smart wasn't seeing a proper voltage drop signal from the stop/start alternator on my Transit — these modern smart alternators mess with the Orion's head something chronic. It reads the variable voltage as "battery not full yet" and just loops absorption indefinitely.

Few things worth checking:

• Are you on the latest firmware? Victron pushed an update a while back that helped with smart alternator detection
• Have you set the charge algorithm to match your battery chemistry? Fogstar and most lithium suppliers have recommended Victron profiles floating about on their sites
• Tail current setting — if it's not configured, the Orion doesn't know when to call it done and move to float

The fix for me was enabling the BMS assistant in VictronConnect and letting the Lynx/BMS tell the Orion when to back off, rather than relying on voltage alone. Game changer.

Anyone else running a Roamer or similar leisure battery on a stop/start van hit this? Curious whether it's more of a battery comms issue or purely the alternator profile confusing things — reckon there's a few setups on here that'll have cracked it differently.

Ben1960 replied:

@ExBrickie94 — the Orion-Tr Smart has a known quirk where if it loses Bluetooth connection to the battery's BMS mid-session, it can't receive the "absorption complete" signal and just sits there stubbornly holding voltage.

Worth checking whether your BMS was dropping connection intermittently — common with Fogstar units when the van's chassis vibration loosens the balancing wires slightly.

Quick fix that worked for me: enable the "tail current" termination in VictronConnect rather than relying solely on the BMS signal. Set it around 2-3% of battery capacity and the Orion will drop to float on its own regardless. Bit of a belt-and-braces approach but saved me the same headache on my camper build last spring.

Also double-check your alternator sense wire is properly grounded — a dodgy ground can confuse the voltage readings entirely.

@Ben1960 mine sorted itself out after I hard-wired the tail current sense wire properly — turns out "close enough" isn't a valid electrical standard, who knew.

@SolarKeith that's interesting about the tail current sense wire — is that the wire going to the battery negative terminal directly, or are some people just tapping it at the busbar and calling it done?

Asking because I've got an Orion-Tr Smart 30A feeding a Fogstar Drift 200Ah and I'm wondering if my wiring is actually correct. The manual isn't exactly crystal clear on where that sense connection needs to land for accurate readings.

Also — does anyone know if the VictronConnect app shows you what the measured tail current actually is during charging? Or does it just show the mode it's currently in? Would help massively with diagnosing whether the charger thinks absorption is done or not.

@CopperSparky — yes, it goes to battery negative, but the critical thing is where on the negative it lands.

I learned this the hard way on my narrowboat. Had the sense wire looped through the bus bar rather than directly at the battery terminal. Orion was reading a slightly elevated voltage due to volt drop across the shunt, so it never registered the tail current dropping — just sat there in absorption indefinitely.

Moved the sense wire to land directly on the battery negative post, keeping it as close to the cell as physically possible. Problem vanished.

Worth checking your Victron documentation too — there's a specific wiring diagram for this scenario. The Orion-Tr Smart is genuinely excellent kit once it's set up correctly, but the sense wiring has to be treated as precision work, not an afterthought.