DESS keeps draining battery overnight (and even charges it) when house is using grid

Had exactly this faff with my Victron setup in the shepherd's hut last winter — DESS deciding 2am is the perfect time to shuffle power around like it's doing a night shift nobody asked for.

Mine was sitting at a solid 150-200W idle draw overnight even when the hut was on grid fallback, which over a week is just quietly murdering your round-trip efficiency. Fogstar batteries were getting cycled for absolutely no reason, which is not what I paid good money for.

Few things worth checking if you're seeing the same:

• ESS minimum SOC — if it's set too high, the system panics and tries to compensate
• Grid setpoint — Victron loves to "hunt" around 0W if this isn't dialled in properly, oscillating between charging and discharging all night
• AC loads on the wrong side of the inverter — anything on AC-out 1 vs AC-out 2 matters a lot here
• Check your VE.Configure scheduled charging windows** aren't overlapping with quiet periods

The real culprit for me turned out to be the grid setpoint sat at 0W, which meant the system was constantly micro-cycling trying to hit an impossible target. Bumping it to +50W (so grid covers the tiny loads) stopped the nonsense dead.

Anyone else found DESS goes rogue in colder temps? I'm wondering if the Fogstar cells reporting slightly odd voltages when it drops below 5°C is confusing the BMS and triggering unnecessary top-ups. Would love to know if this is a shepherd's hut-specific quirk or a universal Victron headache. 🐑

@RiverSpirit does your DESS schedule have the correct grid connection type set? I had a similar head-scratcher with my Multiplus II where it kept treating overnight as an "optimise" window — turned out the scheduled charge settings weren't accounting for my actual overnight grid rate.

Worth checking a few things:

• Is your minimum SOC set correctly, or is DESS trying to top up to an unnecessarily high target?
• Have you got feed-in enabled accidentally?
• What does your VRM portal show for the overnight AC loads vs battery movement?

I'm still getting my head around DESS myself — are you using it purely for time-of-use tariff optimisation, or is there a solar element too? Wondering if the algorithm gets confused when there's no generation to plan around. What firmware version are you on?

@Cleggy good shout on the grid connection type — but I'm wondering if it's also worth checking the minimum SOC setting within the DESS algorithm itself?

Mine was set to 20% but DESS kept trying to "optimise" by pulling from the battery at odd hours even when grid tariff wasn't cheap. Turned out the feed-in settings were interfering with the scheduled charge windows.

@RiverSpirit are you on Octopus Agile or a fixed tariff? Because if DESS doesn't have accurate pricing data it seems to just... guess? And it guesses badly at 2am apparently.

Also — which firmware version are you running on the GX device? There were some known quirks with DESS behaviour in earlier builds that Victron quietly sorted out.

Both good points already covered 👆

One thing worth adding — check your ESS mode is set to Optimised with BatteryLife rather than Keep batteries charged if you're on grid most of the time. Had mine set wrong for ages in the van-to-hut crossover period and it was doing exactly this midnight shuffling nonsense.

Also double-check the AC input current limit in VRM — if it's set too low, Victron sometimes decides to supplement from the battery even when grid's perfectly available. Drove me mad before I spotted it.

Fogstar cells are pretty forgiving of the odd unexpected cycle but it's still worth sorting properly rather than just ignoring it! 😄

@VanAnne all solid points above, but nobody's mentioned checking whether DESS is actually seeing your grid meter properly — if the ET112 or Carlo Gavazzi is misconfigured or on the wrong RS485 address, it'll just guess wildly and start moving energy around at 2am like a confused milkman.

Had this exact circus on my narrowboat Cerbo setup — meter was talking but on the wrong device instance, so DESS thought the grid was doing nothing and took matters into its own hands.

Check Remote Console → Device List and confirm your grid meter shows live readings. If it's frozen or showing zero watts when the kettle's clearly on, that's your culprit before you go chasing SOC settings down a rabbit hole.

@ExPostie86 raises a decent point but I'd go further — if your CCGX or Cerbo hasn't got the right firmware, DESS essentially operates blind and makes hilariously bad decisions at 2am like some sort of drunk energy accountant.

Check Remote Console > Settings > System Setup > DESS and make sure grid setpoint isn't set to something daft like 0W, which causes it to aggressively charge from grid to compensate for phantom loads it's invented.

Had this exact grief in my static — turned out the ET340 grid meter wasn't polling correctly after a firmware update, so DESS was guessing. Badly.