Small house DIY DESS with blackout option - 4,5 kWp - 9,8 kWh

[B51-technician (Alfredo)]

My system – DC-coupled DESS 4,5 kWp - 9,6 kWh

• I have a mid-terraced house with a dormer window, southbound -10°

• Slope 35° and 20°, PVGIS yearly forecast is 5035 kWh

• PV Modules from MAXEON, SunPower Performance 7, 450W

• At the moment, no hourly energy price contract

• Tibber and SmartMeter Gateway expected for May 2025

• SinglePhase MultiPlus II 5000 48V, Grid Code DE, 4,39 kWp

• Multi-Phase Compensation

• Critical loads on AC out 1 (Blackout) of the Inverter

• Heavy loads (Wallbox, Washing Machine, Dryer, Oven) in parallel on grid

• Two MPPT 250/60

• Cerbo GX with Touch 70, Venus OS 3.51

• Two PylonTech BMS US5000 LiFePo4 Batteries, stored in a 19’’ cabinet

• Two Lynx Power-In with Distributor Mod

• GridMeter EM540

Installation

I read the Victron manuals twice upfront, minimum. ESS, product manuals, PylonTech BMS setup, … That helped and the installation was kind of straight forward. Nevertheless, I was surprised about how many different tools, interfaces and protocols are involved until everything is setup: VE Configure 3 for the Inverter, VE.bus interface, VE.direct interface since one Smart MPPT BT connection could not get to work properly and the GridMeter configuration tool. As soon as everything was connected to the Cerbo, firmware updates are easy to deploy via VRM.

The Cerbo GX concept is great. It starts automatically recognizing the connected devices. Configuration is not complicated. DVCC gets enabled or even enforced automatically after the BMS battery detection. Just the MP II needs extra care and extra configuration with the VE Configure Tool. You need to be careful and precise here with correct settings for grid code, currents, assistants and battery parameters. That takes some time and needs focus.

VRM does a great job. ESS as well. Regarding DESS, it’s not always obvious why it takes the one or other decision. A kind of verbose information about the current mode and reason why that mode makes sense might be helpful. DESS is a promising concept, and I am confident it gets mature and better over time.

Trade is not an option in Germany, so I go for green mode at the moment.

What I really did not expect, how noisy a MultiPlus can get in regards of humming and fan noise. My installation is in the basement with a closed door, and I still could hear it in the house. Just the humming already. At the end, I decided to take own measures to get the unit more silent, knowing that it might lead to potential warranty denial. Would love to have a “quiet product option” on Victron side. I even would buy another silent Victron inverter in case that gets available someday.

All in all, I would buy all the components again. The PV modules seem to do a good job, even in cloudy conditions, the Victron products work nicely and have a great quality appearance. The batteries as well and they fit very well into the Victron Ecosystem.

What I love

• Victron components, company and product quality in general

• Victron product website information

• Victron Community

• Modular concept of all components with update and upgrade capabilities

• CerboGX concept

• Venus OS 3.5x and its Remote Console WebApp

• BMS-CAN communication and Battery AutoDetect in GX

• DVCC

• VRM-Portal

• D-ESS basic idea

• Lynx DC Power-In with Distributor Hack

Some thoughts and suggestions

• Offer an optional quiet version (humming and fan) of MultiPlus II 3000 and 5000

• Integrate VE Configure 3 in Victron Connect, including grid code and backup

• Set battery parameters in MultiPlus II automatically from BMS-CAN data

• VE.Can, VE.BMS, VE.Direct, VE.Bus – a little less standards would help, although I understand the history and compatibility topic

• Allow manual input to DESS (multiday absence, abnormal consumption, …) The best statistics cannot predict what I do on purpose in an unusual way. Nothing over-engineered, very simple

• EM540 Grid Meter Victron ready without an own config tool required (feed-in enabled)

• D-ESS strategy – provide a hint, why it behaves like it behaves. Fix some 1.0 bugs like charging from grid right before sunrise on a super sunny day with lots of surplus PV

• I would buy BlueSolar MPPTs with a VE.direct interface. Smart Solar built-in BT is sometimes really challenging. Didn’t get it to work on one of my MPPTs

• Secure VRM DESS “two-way mode” communication. Just allow DESS information to be transferred from the cloud to the GX without granting VRM full access. Add a simple plausibility check. Least privilege principle might be a good idea from a security perspective.

[alexpescaru]

Nice!

That attic at 20° slope will not give you partial shadows for those panels at 35° put so close to it?

[B51-technician (Alfredo)]

@alexpescaru

That attic at 20° slope will not give you partial shadows for those panels at 35° put so close to it?

Well observed, @alexpescaru
Indeed, there is a partial shadow starting at 2 PM on the two modules on the right hand side. I had no choice, since 10cm on the right of the two modules is already my neighbors house. We share one roof. Not ideal, but all in all not a huge loss. The situation is far from perfect for a PV installation, I know.

Find the roof layout attached. I tried to create one string with no shade at all, and one with partial shadow. The string yield with the partial shadow is less than 5% lower.

[alexpescaru]

Construct for 2a and 2b a slope from light materials with the same angle as the attic.
But if the loss is not so big, you can leave it as it is.

Or it’s a reason to consolidate the relationship with the neighbor and/or convince him of the advantages of green energy…

[B51-technician (Alfredo)]

Haha. I thought about both options, @alexpescaru . But my neighbor didn’t want to join the project and the additional yield would not justify a sophisticated construction just for the two panels.

[BjoernK (Björn Kellermann)]

@B51-technician
you could change the string 2A-B to an micro grid inverter with 2 MPPTs, like the HMS-800-2T.
As I have the same issue, a dormer in the midle combined with several trees giving shadow, I decides to us Hoymiles micro grid inverters for 14 panels and use ons tring with 4 panels on the roof top with an MPPT 150/35.
Hoymiles can be integrated into Venus OS using venus-dtu with OpenDTU or AhoiDTU.