Guide to DC Coupled On or Off Grid Victron Systems

While most of us choose to buy AC (Alternating Current) Solar inverters, there is another choice: DC coupled, or DC to battery to inverter/charger systems.  Victron make a line of well respected Inverter Chargers, the Multiplus Range.  Let’s take a look at an off or on grid system, made up of 2 x Multiplus-II, and up to 8kW of Solar panels.

DC Coupled Victron System

The setup here is:

  • 1 x 5.8KWh ecoCool battery (AGM supercycle batteries, 5-8 year life 100% discharge)
  • 2 x Victron Bluesolar 250/60 MPPT solar charge controllers, parallelled
  • 2 x Victron Multiplus-II Inverter/chargers (AS4777 certified – use on or off grid, ESS mode)
  • Victron Color GX Display Panel, to show battery state of charge, AC/Grid/Solar levels
  • Generator control is available via the Color GX (a relay actuated by certain trigger points, like low battery/solar levels)
  • 4 Strings of 300W Solar panels, in this case 7.68KW, (and up to 8KW, for the 2 x MPPTs)

You can buy this package from ecoCool for $14,850.  Installed by a CEC qualified installer, you will get around $4,000 in solar credits, so the net cost will be: $11850 plus installation cost.  Or you can choose components which suit your residence, from ecoCool’s range.

The main difference between a standard, on-grid AC-coupled system, and this DC coupled Victron system, is that the PV power in the AC coupled system, feeds through the AC inverter, which turns it immediately into power.  Usually, to be self-consumed, or sent to the grid, and a feed-in rate.  On the DC coupled system, the Solar feeds through a high efficiency MPPT controller, to charge the batteries, or partly to turn into AC power in the Multiplus inverter/charger.  That is the main difference: the battery is a central bank of power, and the inverter runs power both ways, much of the time taking DC power from the Solar or battery, and creating AC power, and sometimes (especially with a generator), it can charge the batteries.  Victron’s Multiplus and ColorGX allow many configurations, in order to charge, or feed AC into the home, or even turn on the generator, automatically.  Great for off-grid residences.  And perhaps if you have a desire to go off grid, and currently are on-grid.

SMA Sunny Boy energy solar inverter

How to set up your SMA Web Portal for Solar Inverters

SMA make good Inverters. But they don’t make it particularly easy to understand how to setup their Solar Inverters like the Sunnyboy, on the internet portal, so that you can monitor your solar PV installation, and ensure their inverter is working well. Here’s how to set up the SMA Web Portal with your inverter.

SMA Sunny Portal Webconnect Sunny places

Sunny places (for users)
• Sunny places, is a “community” of other users, for comparison
• Plan & simulation of theoretical systems
• Review monitor own system
Sunny portal (for users and installers)
• Is a PV site monitoring web application
• Can be used by users or installer/professionals
• As a “professional package”, it allows solar professionals to monitor clients’ PV systems
• As a “user package”, it allows you to monitor up to 4 inverters
• It provides graphical analysis of inverter/energy management

Webconnect (technology allowing connection to internet)

• This is effectively the internal device software, which allows connection via wifi, or LAN (Ethernet), allowing connection of the device to the Sunny Portal or Sunny Places

Next, I will show you how to connect a Sunny Boy inverter with built-in WiFi to a local wireless network

Home Battery Storage – the Basics

Renewable energy Queensland has produced a really to the point video summarising the basics of using home solar PV systems, with home battery storage:

Home battery systems are about self-consumption of Solar power

Many home owners who have solar power installed, are looking to install a home battery system, to store and self-consume solar power, rather than feed back into the grid to get the often low FIT rate credit. The issues can be framed as follows:

  • Solar PV energy stored in a home battery system can be used at night when the sun is not shining
  • However, storing Solar energy in batteries means you will not receive a “feed-in” tariff credit while charging
  • When you self-consume solar energy, instead of feeding it to the grid, however, there is a cost saving to you
  • Self-consumption saves the higher cost of grid power at night, which costs around 25c/unit (kWH)
  • So instead of paying the 25c/unit for power at night, you use battery stored solar power, but don’t receive the approximately 10c/unit, not selling that stored solar energy
  • Put more simply, if you store solar in a home battery system during the day, you lose the 10c feed-in tariff for that energy, but you don’t have to pay the full rate of 25c for power at night
  • You save 15c per unit of power you store in a home battery system, and self-consume at night, or at times of high demand

For well matched battery, solar system, and home energy use, the ideal is to self-consume your solar power, so that there is a net zero exchange of power between the grid and your home.  If you can achieve that closely matched system, the savings you make over time, can effectively mean payback of a home energy storage system, within 3-7 years.

See ecoCool’s Solar Insight Excel spreadsheet to do a quick calculation to see how to create that ideal system match with your solar PV and home energy use scenario.