Anyone else had grief with a Sargent EC155 draining the leisure battery overnight?

Had exactly this on my old Elddis before I stripped most of the Sargent system out. The EC155 has a known issue where the "battery protect" logic doesn't actually disconnect cleanly — there's a parasitic draw through the control board itself that can pull 30-50mA continuously even when everything appears off. Over 10-12 hours that's genuinely enough to flatten a tired 100Ah leisure battery.

Few things worth checking:

• Measure the actual standby draw with a clamp meter or a decent inline ammeter between your leisure battery negative and the EC155. If you're seeing anything above 10-15mA at rest, the board is suspect
• Check the relay on the unit — they do fail partially, leaving a small bleed-through
• Firmware — some EC155 units shipped with early firmware that made this worse, though getting Sargent to acknowledge this is like drawing blood from a stone

My longer-term fix was fitting a Victron BatteryProtect 65A inline, which gives you a proper hard disconnect based on voltage threshold. Paired with a Fogstar Drift 100Ah lithium it transformed the reliability completely. The Sargent box still handles the habitation stuff but it's no longer trusted to protect the battery by itself.

Anyone else finding this is more common on units made before 2019? I've seen several posts elsewhere suggesting a batch issue but nothing confirmed. Would be useful to know if there's a pattern with build dates — worth noting yours if you've reproduced the drain.

Really glad you've flagged this @LakelandNomad — and if anyone's stumbled onto this thread whilst troubleshooting a mystery drain, welcome to the forum, you're in exactly the right place.

To add something not yet mentioned: the EC155's parasitic draw issue is often compounded by whatever 12V loads are downstream of it. Worth putting a clamp meter on the feed before assuming the EC155 itself is the sole culprit — I found a poorly-wired USB panel was masking where the real draw originated on my van build.

If you're considering replacing the Sargent system entirely, a Victron BatteryProtect paired with a proper BMV battery monitor gives you actual data rather than guesswork. Fogstar batteries also have decent low-voltage cutoff behaviour that adds another layer of protection.

Swapped out the Sargent nonsense in my shepherd's hut build for a Victron BatteryProtect and a Fogstar Drift LiFePO4 — best thing I ever did, though admittedly my hut doesn't move, which does rather simplify the diagnosis process. 🔋

@BatteryPaula pretty much mirrors my experience. Pulled the Sargent unit off my boat's 12V system after similar overnight drain issues — not a motorhome setup but the EC155 logic is the same rubbish regardless of application.

What caught me out was the parasitic draw wasn't consistent. Some nights fine, others it'd pull 2-3A continuously for no obvious reason. Took a clip-on ammeter on each circuit to isolate it properly.

Replaced with a Victron BatteryProtect 65A and haven't looked back. Costs more upfront but at least the disconnect threshold actually works reliably.

One thing worth checking before you bin the whole unit — are you on LiFePO4 or lead-acid? The EC155 voltage thresholds are calibrated for flooded/AGM, so if you've swapped to lithium without reconfiguring anything, it'll behave erratically almost by design.

Been lurking on this thread because I've got an EC155 in my Transit conversion and started noticing exactly this — woke up to 11.8V after a full day of solar the previous afternoon. Stuck a clamp meter on the main negative last night with everything switched "off" and measured just over 40mA quiescent draw through the Sargent loom. Not catastrophic on its own but it's relentless — eight hours and you've lost a fair chunk from a 100Ah battery, more so if it's AGM with a steeper discharge curve.

@BatteryPaula the Victron BatteryProtect is on my shortlist. Does yours handle the load-side disconnect cleanly with inductive loads, or did you need a relay in line for anything motor-based?