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

Had this exact issue on my previous van build. The EC155 has a standby draw that Sargent are a bit cagey about publishing — from memory mine was pulling somewhere around 8-12mA constantly, which sounds trivial but adds up badly if your leisure bank is on the smaller side or partially sulphated.

Worth getting a proper clamp meter on it rather than guessing. I used a Uni-T UT210E and was genuinely surprised what I found lurking.

A few things to check:

• Is the EC155 actually going into its low-voltage disconnect mode properly? Mine wasn't, turned out to be a calibration drift issue
• Any 12v devices plugged in downstream that you think are off but the EC155 is still feeding?
• How old is the leisure battery? A tired AGM will show resting voltage that looks fine but collapse under even tiny parasitic loads overnight

I've since moved everything over to a Victron based system with a SmartShunt so I can actually see what's happening in the Victron Connect app — the visibility alone is worth the switch cost.

That said, plenty of people run EC155s without drama. The units aren't all bad, some are just... inconsistent quality control from what I've seen discussed on here previously.

What leisure battery are you running? And is this a recent drain issue or has it always done it? Would help narrow things down considerably.

@HollyBaker 8-12mA is actually on the generous end — mine was closer to 18mA on a warm evening, measured with a clamp meter inline. Doesn't sound like much until you do the maths: 18mA × 24 hours = 432mAh per day, and that's before anything else is ticking away in the background.

What finished it off for me was running a 100Ah AGM. By March the battery was sulphating badly because it kept sitting at 40% or lower.

Swapped to a Fogstar 100Ah lithium and wired a simple Victron BMV-712 to monitor the resting draw properly. Night and day difference.

If you're staying with the EC155, fit a latching relay on the main feed and kill it properly when you park up. Sargent won't tell you to do that, but it works.

@MountainHermit 18mA doesn't sound dramatic until you realise that's roughly 432mAh overnight — enough to notice on a modest 100Ah leisure battery, and absolutely murderous if you're already limping into winter with a knackered Fogstar cell or two!

Worth adding: a cheap smart relay wired to cut the EC155 off the battery when the ignition's off sorts this overnight bleed entirely — I did exactly that on the narrowboat's 12V system (different beast, same parasitic draw headache) and the Victron BMV-712 stopped giving me the side-eye every morning.

Takes about an hour with basic crimping skills and costs under a tenner from any motor factors.

@CornishNomad that 432mAh figure compounds nastily if you're already dealing with a partially discharged bank or cold weather knocking your capacity down.

On my narrowboat I ran into something similar with a different unit — ended up fitting a Victron BMV-712 specifically so I could see exactly what was draining overnight rather than guessing. Pinpointed a 23mA phantom load I'd never have found otherwise.

Worth isolating the EC155 completely with a small relay on a timer if you genuinely need it in standby — some folk just switch it off at the fuse when they're not actively using 12V circuits. Not ideal but on a modest 100Ah bank even "small" parasitic draws add up across a week of limited solar input.

@HeatherSoul absolutely — and this is where people go wrong thinking "oh it's only milliamps." On my narrowboat I've got a Victron BMV-712 logging everything, and the cumulative picture of parasitic draws across multiple devices is genuinely eye-opening once you start adding them up properly.

Worth noting with the EC155 specifically: there's a relay inside that you can isolate with a simple switched line, effectively cutting standby draw to near zero when you're not using 12v facilities. Few people realise this is an option.

I'd also strongly suggest anyone chasing phantom drain issues grabs a cheap USB power meter or a clamp meter and methodically pulls fuses one-by-one at the fuse board. Sounds tedious but you'll find the culprits sharpish — took me about 20 minutes to discover my old inverter was the worst offender, not the Sargent unit at all.

@Boycie narrowboats are exactly where this lesson bites hardest — I learned it the painful way on mine before I fitted a Victron BMV-712 and actually saw what was happening overnight. The EC155 isn't alone either; I've caught similar parasitic draws from cheap 12V USB panels and even a Renogy DCC50S left in standby.

The real issue is these draws are invisible until you're staring at a flat bank on a cold January morning wondering why your 200Ah Fogstar lithium is sitting at 40%. Now I religiously log my overnight idle draw — anything above 5mA and I'm hunting with a clamp meter before I sleep. On the shepherd's hut build I'm planning, every circuit gets a proper isolation switch for exactly this reason.