Zwei Männer am Tablet in Forschungsabteilung
Vanadium Redox
Flow Technology
Redox Flow

The most durable storage technology for your home.

Vanadium redox flow technology (VRF) has been successfully used for years as a large-scale storage technology for photovoltaic and wind farms. For the first time, VoltStorage takes the world’s most durable storage technology into your own home and offers a pioneering alternative to lithium-ion storage – “Made in Germany”.

Operating principle of the vanadium redox flow storage technology.

In contrast to conventional storage systems based on lithium and lead, vanadium redox flow storage technology (VRF) uses a vanadium-based electrolyte liquid as storage medium. The liquid electrolyte is held in two separate containers (a total of 220 litres), each with different oxidation levels.

The electrolyte liquid flows through two closed circuits and is pumped through high-performance battery cells produced via a novel, patent-pending production method by VoltStorage. These cells consist of two half cells separated by a membrane.

During the charging process, the photovoltaic system supplies the battery cells with electricity. This triggers different chemical conversion processes:

While the electrolyte is chemically reduced in the negatively charged half-cell, in the positive half-cell the electrolyte is oxidized – hence the term “redox”. The electrons released in the positive half-cell migrate via graphite electrodes into the negative half-cell which is also supplied with released ions from the positive half-cell through the membrane. This results in a conversion process from electrical to chemical energy.

As soon as the solar energy stored in the electrolyte liquid is needed for TV, washing machine etc., this process is reversed: Chemical energy becomes electrical energy again and enables more independence even when the sun is not shining.

Positively charged electrolyte tank

In the uncharged state, the positive electrolyte circuit contains vanadium ions with an oxidation state +4. In this state the electrolyte takes on a blue colour. Once it is supplied with the power that is to be stored, the vanadium ions oxidize and assume the oxidation state +5. When the storage system is fully charged, the positively charged electrolyte circuit only contains vanadium +5. The electrolyte then shows a yellowish colour.

Negatively charged electrolyte

In the uncharged state, the negative electrolyte circuit contains vanadium ions with an oxidation level of +3. This causes the electrolyte to take on a blue-green colour. Once it is supplied with the power that is to be stored, the vanadium ions reduce and assume the oxidation state +2. When the storage system is fully charged, the negatively charged electrolyte circuit only contains vanadium +2. The electrolyte then has a purple colour.


The positively and negatively charged electrolyte is fed into the battery to initiate charging and discharging processes. The membrane keeps both electrolyte liquids separate to ensure the efficiency of the battery system. However, the membrane is ion-permeable, so that during charging and discharging the ions cross the membrane to complete the electric circuit. This allows for electrical energy to be stored through a redox reaction, which converts electrical into chemical energy.

Pumping System

The pumping system is responsible for feeding the vanadium electrolyte into the battery. The internal battery management ensures that the quiet pumping system is only activated whenever necessary. This guarantees that the pumps are used efficiently.

The most durable storage technology.

Mittelfristige Kapazitätsverluste sind bei herkömmlichen Speichersystem die Regel. Der Grund: Mit jeder zusätzlichen Be- und Entladung bilden sich elektrochemische Ablagerungen an den Elektroden der Batterie – die sogenannte Dendritenbildung. Diese führt unter anderem dazu, dass die Speicherkapazität über die Zeit kontinuierlich abnimmt. Die Lebensdauer markttypischer Stromspeicher auf Lithium- und Blei-Basis ist somit begrenzt.
The situation is different with vanadium redox flow technology: Due to the liquid electrolyte, such capacity-reducing mechanisms are eliminated 100 percent thanks to VRF technology. Our storage system can therefore be loaded and unloaded as often as required without losing any capacity. The result: More than 10,000 charging cycles without self-discharge and capacity loss.

Innovative storage technology ``Made in Germany``.

The vanadium redox flow storage technology has already been used successfully for years to store wind and solar energy in large-scale storage systems. It was only in 2017 that the largest battery in Germany was installed at the Fraunhofer Institute in Pfinztal – based on VRF technology. VRF battery stacks could up to now only be manufactured manually, hampering production for the home storage market.
An automated patent-pending production process makes us the first company in the world to offer home battery storage based on VRF technology cost-effectively. Thanks to our development team working in Munich, the battery stacks are developed and produced in-house – and thus 100% in Germany.
Technologie-Abteilung der VoltStorage GmbH
VoltStorage development department with Dr. Mardilovich (left) and Dr. dos Santos (center).

Why VoltStorage Home Battery?

The ecological alternative to lithium

Lithium-based power storage systems must be questioned in ecological and humanitarian terms. Thanks to our vanadium redox flow storage technology, we offer homeowners a sustainable alternative for the first time. Because it is finally time to take a new path.
More about the ecological alternative

More energy independence

Use more if the self-generated solar power at home and thus save on your electricity bill – with our power storage device you and your family gain more independence from the energy market and rising electricity prices.
How to become more independent

Storing power - safer than ever

Conventional lithium- or lead-based power storage systems cannot guarantee full operational safety. Thanks to our vanadium redox flow storage technology, you can rely on the only storage system that is 100% non-flammable.
This is why VoltStorage is so safe

Environmental protection with battery

Rising temperatures around the globe represent one of the greatest challenges of our time. We face up to this challenge and enable you to improve your CO2 balance by using our battery. Because with VoltStorage you can prevent the release of up to 800 kg CO2 per year.
More about environmental protection

Transparent all-in-one service

With VoltStorage you can sit back and relax. We make sure that your storage system is compatible with your house and professionally installed – at a low, all-inclusive price. With the VoltStorage App you can also view the most important storage data.
Our all-in-one service

The most durable battery storage system.

Store and use your solar power over many years with 100% capacity guarantee – only possible with VoltStorage’s durable and powerful vanadium redox flow storage technology. Learn more and request an offer including installation:

VoltStorage Stromspeicher
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