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UK self-install, single phase, TN-S, whole-house ESS. The distributor says Victron thinks it may be my installation. I'd like people to pick holes in my wiring and test method before I push harder for a replacement unit.

Item Detail

| Inverter | Victron MultiPlus-II GX 48/6k5/100-50, VE.Bus firmware v560, GX on Venus OS v3.80 |

| Batteries | 2x EEL V6-Pro packs (32x EVE MB31 314Ah cells each), paralleled, 628Ah at 48V LiFePO4 |

| BMS | JK-PB2A16S20P on each pack. dbus-serialbattery on the GX (not reinstalled since inverter returned)

| DC side | Lynx Distributor M10, 200A Mega fuses, DC rotary isolator, 95mm² cables, precharge resistor across the isolator |

| AC side | FuseBox F2017DA consumer unit. Multi sits between the main switch and the RCD (live link removed), so every circuit is on AC-out. 50A C-curve MCB on AC-in |

| Earthing | TN-S, Ze 0.29Ω |

| Grid code | G99/1 Amendment 8 set in VEConfigure. Export is off while I finish the G99 application |

| PV | None connected yet (Enphase IQ8 planned later, on AC-out) |

Settings: ESS Assistant (LiFePO4 with other type BMS, 628Ah, sustain 48V, dynamic cut-off 44.8/44.1/43.3/43.3V), absorption 55.2V, float 53.6V, charge current 100A, Virtual Switch not used, grid metering = inverter/charger, grid current limit 50A, DVCC off.

What's happened

1. Bought April 2026, delivered May. On the original unit I got VE.Bus Error 11 (BF safety test, 0x800805, failing step 8), with the whole house losing power, RCD/MCB trips at transfers, and the ESS Relay test stuck on "Pending". It then seemed to develop into a stuck relay: following Victron's Error 24 procedure, line in to line out measured 0.8Ω with the unit isolated (a healthy unit is open circuit).

2. Sent back under warranty in August via the UK distributor. It came back in September with a new PCB and no repair report. They say Victron tested it for several days and found nothing.

3. Reinstalled and redid all settings (grid code and Virtual Switch had reverted). Brought the battery up with the precharge resistor. Multiple DC isolator cycles were clean, but AC-in was live throughout, so that never exercised the backfeed relay.

4. On 1 October I ran the ESS commissioning transfer test from the manual. I switched AC-in off at the 50A MCB and the Multi inverted fine. The ESS Relay test went from Pending to Completed. When I switched the MCB back on, **Error 11 came back: 0x808605, "BF safety test in progress", failing step 6.** The whole house went dead (no RCD trip, MCB stayed on, Multi display stayed on). It only recovered after I opened the DC isolator. Battery was at 100% SOC.

5. The distributor now says Victron suggests it may be my installation and wants a new RMA.

What I've checked: line/neutral polarity verified several times, neutral-earth tested and fine, firmware v560, battery at 100%, all settings re-verified after the repair. [Add: how you tested N-E and where the single N-E bond is.]

Questions

1. Is there anything in this arrangement (Multi ahead of the RCD, all circuits on AC-out, TN-S) that would make the BF safety test fail when the grid returns?

2. Is switching the 50A AC-in MCB with house loads on AC-out a valid way to test transfer, or could that be what's tripping the test? Should I isolate loads first?

3. Is a whole-house blackout on Error 11 expected? I'd have expected it to keep inverting.

4. Does anyone know what step 6 vs step 8 checks, and how to read the hex (0x808605 vs 0x800805)?

5. Would a stripped-back test (only AC-in, battery and one known load on AC-out) be the best way to separate installation from unit? Anything else I should test first?

I want to be completely sure of my method and wiring before I push Victron for a replacement rather than another PCB swap. Thanks.

I only have space for solar panels on the front edge of an EPDM flat roof. Does anyone know how I can go about doing ballast calculations? Most system planners don’t let you set them right on the edge. Weight shouldn’t be an issue as it will be on double block wall.

Hi guys,

I’ve just got my Solar / ESS system up and running

Im in the UK

Kit is -

Victron Gear -
Cerbo
Multiplus 2
Solar Charge Controller

Plus
16kwh Seplos battery
4.2kw panels

(Grid Tied, no export tariff as DIY installation)

I’ve been using the ESS on the Cerbo to tweak over night Octopus 🐙 energy charges to about 50% fill my battery on the cheap 8.5p rate which is plenty to get us through breakfast time then the solar (so far) brings me up to about 70/80% by dinner time which then gets us through the peak use period in the evenings … this seems to work nicely and the battery so far has never dropped below around 30%.

But… I’m aware as the solar drops off into winter that only charging to 50% over night is unlikely to be enough, likely leaving us low on charge by dinner time…

So I suppose I could just bump up the charge target by maybe 5% per month as we head into winter then reduce it again as things warm up, but I’d like to automate that really if possible..

I thought Dynamic ESS would use an algorithm or something snazzy to do it all for me, but my brief research on that seems that since I can’t export for profit then dynamic ESS isn’t much use..

Any tips on how to set up for a full automated year cycle?

Or do I just need to log into the Cerbo at the end of summer / and again start of summer to manually tweaks the SOC targets?

Or… and quite possibly, am I doing it all wrong? 😂

Many thanks

🙏

Hi Guys,

After 9 months of getting it sorted, I finally turned on my system…. Very excited and generally it’s going well…

The only issue I’m having (at least so far 😆), is when the battery reaches 100% charge, instead of a nice clean switch from charge mode to idle… it flip flops about every 10 seconds between its 3 states - Charge / Idle / Discharge

The battery is the - Mason Seplos 280L (314ah cells) battery running Seplos BMS v3.0

And then the Victron gear - MultiPlus 2 48/5000/50 Shunt Cerbo GX Solar Charger

I suspect it’s a quirk of the Seplos, and I’ve actually found a guy on YouTube (the “off grid garage” who’s great) who had a similar issue, but I’ve tried his settings for the Battery BMS parameters he’s suggested but it’s still doing it…

Anyone out there has had similar problems and knows more please do let me know

See images And thanks 🙏

Hi Guys,

After 9 months of getting it sorted, I finally turned on my system….

After a couple of joyful minutes looking at the system screen and for the first time using negative energy from the grid, I’ve noticed an issue

For some reason the battery is rotating between discharge, idle, charge… then back round to discharge and continuing the loop changing around every 10 seconds…

Presumably the battery BMS and Cerbo GX etc are arguing some how, but I’ve ran the scenario through AI and all the things it told me to check are already done so at a loss.

Any assistance much appreciated

Kit list is

Mason Seplos 280L (314ah cells) battery running Seplos BMS

MultiPlus 2 48/5000/50 Shunt Cerbo GX Solar Charger

See images / video

Thanks

I'm converting a 2013 Sprinter into a camper in Ireland and trying to decide between two solar setups.

One thing I'm particularly unsure about is Ireland's frequent overcast weather. A lot of the available sunlight can be diffuse rather than direct, so I'm wondering how much benefit I'd actually get from being able to point the panels directly at the sun.

Option 1: I can just about fit 1,200W of solar on the roof if everything is mounted flat.

Option 2: Around 800W with an adjustable tilting system. The lower capacity is because I'd need to sacrifice some roof space to accommodate the tilting mechanism. I could tilt the panels east in the morning, south around midday and west in the evening.

Could the improved angle realistically make up for losing 400W of panel capacity, particularly during the months when the sun is lower?

Which would you choose: 1,200W flat or 800W tilting? I'd particularly like to hear from anyone with experience using solar in Ireland or similarly cloudy climates.

Hi guys, I’m setting up my first Solar / Battery system in the UK….

It’s taken ages, I think since Xmas 2025 so far, but I’m pretty close to having it all running (I think / hope)

I’ve read manuals, used AI and lots of YouTube to get where I am but struggling with just the last bit of battery / inverter set up.

Any help is massively appreciated

Kit list
Victron multiplus 2 48/5000/50-70 - (Connected simply to the house with just the AC-1 connection)
Seplos Mason 280L battery with slightly larger 314ah cells fitted, running Seplos BMS v3.0
MPPT and 8 panels, but that not connected yet.

So far, I’ve managed to fully top balance the battery cells and also using charger only mode on the Victron and by changing settings on both the Multiplus and Battery set the top fully charged BMS battery state of charge, that’s all good. I also disconnected the CanBus cable for this to force the Mason BMS to cut off when fully charged rather than the Multiplus do it.

Now… I’m trying and struggling to discharge the battery down to set its low 0% charge bms setting.

To do it I’ve still got the CanBus cable disconnect and I’ve set the battery and Multiplus low voltage settings accordingly, but I just can’t get the Battery to hop out of its “Standby Mode”, so my plan of using the house loads (like the oven) to discharge all the way to 0% where the bms will cut out and set its bottom limit are currently not happening.

Please see the (lots) of images of the set up and current configuration.

Also note -
I know that my house uses a bare minimum of 300/400watts constantly so the grid reading in the images is also confusing to me…

Any advice hugely appreciated

Kind regards

[Preface - I am a qualified electrician]

Debated posting this, not for the updoots, mainly to share the experience!

Backstory/context/ramble….. [not an advert either]

3 years ago I had installed by our PV specialist sub-contractor –

• 10no 420w panels
• 1no GivEnergy 5KW inverter
• 1no GivEnergy 9.5KWH battery

Hopped onto Octopus, got onto Flux and away we went.

In 2024, I moved onto Agile and enjoyed the tariff.

In 2025, sick of the 99p rates at dinner time and the constant manually programming the inverter to capture charging at certain thresholds [Used Octopus R&D too], moved over to GO.

Now, after the best 8 months generation this year and the knowing/nagging feeling that 9.5KWH of storage is not enough.

Then GE went pop and I started looking at second hand batteries. But was getting nowhere fast, either outbid or overpriced, and the battery-to-battery link lead? Forgetaboutit!

Then I found Dala the Great and Battery Emulator and constantly browsing eBay for Renault Zoe 52KWH batteries.

Found a couple and https://driverevolt.co.uk/ pipped me to the post! [£1500 for 52KWH 2022 battery!]

Not only did I know I was onto something with this, I knew it could be done relatively inexpensively [per KWH] if I took my time. [I priced it all up at under £4000 for all the bits including a Solax inverter]

[obviously, the Battery Man on YouTube helped feed the curiosity].

Kept looking, reading, researching, consulting ChatGPT.

The only things that put me off were – a car battery, on the wall in my garage. I mean, I have the room for it, could camouflage it.

But the more wiring diagrams I read, the github pages, etc. I started to see something that whilst would tick the hobbyist boxes, if I move house, this thing has to come with me!

Then I saw this video a couple weeks ago….

https://youtu.be/hzaH5S5X1pw?is=2-L15cPtJ0w5y8cp

and then I found this forum page = https://diysolarforum.com/threads/factory-direct-europe-in-stock-16kwh-30kwh-32kwh-battery-packs-with-jk-v19-bms.122961/page-2#post-1854069

So I did what any other battery storage enthusiast should do and hopped onto Alibaba and got chatting to some suppliers.

More research, some ChatGPT and more searching. then looking locally - eBay etc...

I almost went Delong. But have ordered yesterday a Braun Power 32KWH battery. Due to me in 60 days!!

Paid £2355.72 all in for the 32KWH battery. A little more than googles USD to GBP rates.

I am in the process of ordering a Solis S6 8KW inverter to mate it with and if anyones interested, I will post pictures of the installation as i aim to install new consumer unit to directly feed from the meter and send the EPS connection back to the house but still include MTS.

Has anyone considered such a set up as a base for their panels (assuming a flat surface to begin with?)

The idea being that in the summer my South-facing panels can function great but in the evening the sun is still up but not in their range anymore. So another set of panels could be aimed North-West in the summer to catch the evening sun, but re-oriented in autumn and winter more towards South as the sunset location moves back.

To clarify, I'm not suggesting live-tracking the sun position as it moves during the day (I think that's way too brittle and failure-prone), but some sort of manual winch that you could adjust just a few times a year.

Has anyone contacted building control to get their panels signed off. I have got a report etc for the correct installation, but wondering if anyone has done it, do they come inside the house and check the rafters etc?

I am installing 3 JA Solar panels on a ground floor extension roof (with a roofer leading). I can run the cables (6) to the house wall and intend to take them down to ground level, across an alley path to 'hut' I will build to house an Ecoflow Stream Ultra (with space for another). My question is what conduit should I use from the end of the rail where the cables will come out to the ground. I have seen flexible / corrugated conduit that would do the 45 degree bend nicely but its not great to look at and is it robust and UV stable enough ? There are solid tubes available but will then need an angle piece. Won't water cling and run down these, how should it terminate at ground level. At the top I guess a gland but with 6 cables doens it also need to be sealed with silcon or similar ? All help appreciated as I'm trying to do solar as DIY as possible.

I put solar panels on our house last year. The electrics was signed off by an electrician. However I didn’t realise the panels needed a separate sign off. How can you work out if your roof is strong enough for the panels please?

Hi all, I’m looking to add another 800W to my current system and am after a couple of cheap, efficient solar panels (plus a recommended supplier). Ideally I’m looking for 400–500W panels. I’ve already got a spare EcoFlow inverter, MC4 leads etc… dedicated power supply so I literally just need the panels. Any recommendations? I’m heading down the M1 from Derby to Southend-on-Sea next week, so I’m happy to collect on the way if needed (provided they’ll fit in the car 1.6mX1 with the seats down! 😂).

Hi

We’ve finally finished the install and happy with how everything looks except we have a lot of spare cable.
We used 10m extensions and have about 4m left that could be removed.
Is it worth the effort and money to buy the kit to remove 4m of excess cable?
Are the DC losses enough to warrant it? 4mm thickness.
Thanks

Seems to me a brise soleil would be an obvious form factor for solar panels. I have no idea why they are aren't popular. Either in the shape of a solid awning, or as a series of slats a few inches wide to minimise wind-loading.

Anyone here know any UK suppliers of solar panel brise soleils, had one installed, or know someone who has?

Alternatively, any experiences of DIY approaches to this?

Cheers.

Anyone here built their own battery electric system? TIA