Tech-Tuesday

Victron’s BatteryLife Advantage

Nicholas Herbst
General Manager

5 September 2023

Victron Energy Storage Systems (ESS) are leading the charge in dependable, high performance and high quality power solutions in South Africa. Having been in the industry for almost 50-years, Victron Energy has developed hardware and software solutions to position itself at the pinnacle of the industry, cemented by strong R&D and high-quality products.

Today, in our Tech-Tuesday, we’ll be highlighting one of Victron’s great innovations, the operating mode called “Optimised with BatteryLife”. 

In a Victron ESS, renewable energy is prioritised to be served to the Loads first (Consumers of electrical energy / AC Appliances). Any excess renewable energy (solar power, specifically) is then used to charge the battery, and then any further excess solar power may be used to export power to the Grid (if permitted and configured to do so).

The term “Loads” consists of the SUM of Essential and Non-essential circuits on the premises, also referred to as “Critical Loads” and “AC Loads” by Victron.

In the illustration above, the total consumption (Loads) is indicated to be 1325W, which consists of 1010W of Non-Essential / AC Loads and 315W of Essential / Critical loads. 

Here, the renewable energy consists of solar power, as well as solar energy that has been stored in the battery. The extent of battery usage (renewable energy) is defined by a simple system setting called the Minimum battery state-of-charge (SoC) – “Minimum SoC”, where this setting defines the battery level at which the system shall stop discharging the battery, and reserve the remaining battery energy for a Mains power failure. Once the battery level reaches this set-point (e.g. 50%), the inverter system will seamlessly transition to supplying the Loads from Mains power. 

In the illustration above we can see that live solar power generation (PV Charger) is indicated as 1898W, while the battery is discharging, from 96%, in support of the solar power, at 2956W. The combination of the solar AND battery power is offsetting the total Loads (essential and non-essential), leaving just a small contribution from Grid of 99W.

In the illustration to the right, we can see that the system is configured with a Minimum SoC setting of 40%, which means that the battery will stop discharging energy once it reaches 40%, leaving the remainder for backup during a Mains power failure (e.g loadshedding). An easy slider allows for rapid and convenient adjustment of the Minimum SoC setting, whether from the smartphone App or the comfort of your laptop/desktop. 

While this seemingly provides robust control, how does an installer or end-user recommend or choose an optimal Minimum SoC value?

The above question presents a dilemma for many power systems, specifically due to the typical seasonal changes in home energy consumption as well as the potential seasonal changes in solar energy production. 

Well, so what? What are the risks? 

In the absence of pro-actively monitoring and regularly adjusting the Minimum SoC setting, the user could experience several performance compromises, including: 

  • Curtailed solar energy yield
  • Insufficient stored battery energy to sustain operation during grid failure
  • Battery SoC % drift due to infrequent synchronisation
  • * Battery cell imbalance due to insufficient duration spent within the balancing threshold of the battery management system (BMS)

*Assumes system is equipped with a battery that utilises a BMS (e.g. most commercially available lithium battery products).

Victron’s answer to this is a clever algorithm, called “Optimised with BatteryLife”. BatteryLife tries to ensure that the battery will always be recharged to 100% SoC – every day. This is how it works: 

During periods of poor weather when solar energy is reduced, BatteryLife will dynamically raise the Low SoC limit which has been set. This has the effect of making less power available for consumption. It raises this level by 5% each day until the energy which the system draws from the battery during a 24hr period matches the energy being replaced. The aim is for the battery to operate at or near 100% SoC.

When weather conditions change, and more solar energy becomes available, the system will once again lower the Low SoC limit, day by day, making more battery capacity available for use (it will eventually return to the user-preset limit) – whilst still ensuring that the battery SoC ends each day at or close to 100%.

In the illustration above you can see the BatteryLife algorithm at work. The blue chart shows the “Active SoC” percentage, for a particular installation site, starting at 70% in the middle of August and reducing gradually down to 40% by the beginning of September. This coincides with the warming weather that was experienced from the middle of August and a corresponding reduction in the installation site energy consumption. The BatteryLife feature ensured that solar energy yield was optimised, while still maintaining the customer’s minimum reserve energy for sustained operation during Mains failure.

In the illustration to the left, we can see that the BatteryLife feature has identified an Active SoC Limit of 40%, even though the user has indicated and set 20% as their Minimum SoC setting. In this instance, the system will stop discharging the battery at 40%, effectively reserving more battery energy for backup and promoting the battery to reach 100% through charging from excess solar power. 

Many battery products are mandating this feature be enabled in Victron equipped systems as it not only promotes optimal performance of the battery product, but the whole system too.

Victron’s BatteryLife feature allows users to retain control, but with the convenience of automation powered by machine learning. This feature marries convenience with performance optimisation, and is a giant leap forward in the pursuit of a completely self-managed and autonomous power system.