variostring vs 120, 900V input for one solar string or 600V for two strings
high-end Swiss-made high-voltage solar charger
vs 120, the flexible charge controler for various configurations
The variostring vs 120 MPPT solar charge controller is designed to work with one PV string up to 900 Vdc or two strings of 600V. Reducing cable sizes and installation costs while delivering outstanding performance. It operates together with the xtender or next series of inverter-chargers to build complete solar systems. It can also work alone in 48V systems for example, in a telecom system. The vario chargers have been used in standard solar systems as well in special applications (hydro, DC/DC converters, DC minigrid).
vs 120, the flexible charge controler for various configurations
The variostring vs 120 MPPT solar charge controller is designed to work with one PV string up to 900 Vdc or two strings of 600V. Reducing cable sizes and installation costs while delivering outstanding performance. It operates together with the xtender or next series of inverter-chargers to build complete solar systems. It can also work alone in 48V systems for example, in a telecom system. The vario chargers have been used in standard solar systems as well in special applications (hydro, DC/DC converters, DC minigrid).
100% offgrid/ongrid
World champion for efficiency in isolated converter with >98 % and high MPPT tracking efficiency >99.8%
Low standby consumption (<1.25W) is perfect for an offgrid system.
Directly compatible with our xtender series of inverter-chargers and our next series with the xcom 485i for offgrid/ongrid installations.
Practical
Various possible configurations of the two PV inputs (series, parallel, independent).
Reduces expensive wiring with higher voltage.
Adaptable with access to more than 200 settings.
Scalable with multi-unit options up to 15 units with the xtender series of inverter-chargers (105kW) and 5 units with the next series (35kW).
10 years warranty
Choose your energy source
solar panels
hydro DC power
wind DC power
and more…
100% offgrid/ongrid
World champion for efficiency in isolated converter with >98 % and high MPPT tracking efficiency >99.8%
Low standby consumption (<1.25W) is perfect for an offgrid system.
Directly compatible with our xtender series of inverter-chargers and our next series with the xcom 485i for offgrid/ongrid installations.
Practical
Various possible configurations of the two PV inputs (series, parallel, independent).
Reduces expensive wiring with higher voltage.
Adaptable with access to more than 200 settings.
Scalable with multi-unit options up to 15 units with the xtender series of inverter-chargers (105kW) and 5 units with the next series (35kW).
10 years warranty
Choose your energy source
solar panels
hydro DC power
wind DC power
and more…
Designed for a wide range of uses
Flexibility of use for your applications
offgrid and backup application
solar autarky (self-sufficiency) with our next series of inverter-chargers
minigrids application
on board power
mobile application
telecom application (48V DC systems or 230V AC with inverters)
hydro DC power
wind DC power
and more…
What customers think of vs 120
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Swiss made 
Proudly designed, assembled, and tested in Switzerland, ensuring the highest standards of quality and reliability that Studer Innotec is known for.
Every unit undergoes strict controls to ensure performance, long-term durability, and seamless operation in the most demanding environments.
With Swiss made excellence, the variostring will ensure optimal charging and longer battery life.
Swiss made
Swiss made
Proudly designed, assembled, and tested in Switzerland, ensuring the highest standards of quality and reliability that Studer Innotec is known for.
Every unit undergoes strict controls to ensure performance, long-term durability, and seamless operation in the most demanding environments.
With Swiss made excellence, the variostring will ensure optimal charging and longer battery life.
900V solar string
The vs 120 has 2 MPPT inputs that can be wired with a lot of flexibility. It allows PV modules to be connected in series to create a string up to 900 V, minimizing current and reducing cable sizes. The two inputs can be wired to two independent strings up to 600V, for example, to cope with different orientations on the roof. The inputs can also be wired in parallel for arrangements with higher current.
Solar DC coupling for greater efficiency
With DC coupling, our solar charge controllers variotrack or variostring feed energy directly into the batteries for greater storage efficiency.
A wide range of battery compatibility
The variostring is compatible with all 48V battery chemistries (lithium, lead, Na+…), either communicating or not. A very flexible battery profile configuration helps you to adapt to each technology.
Adaptative management of batteries
With more than 3 decades of expertise in offgrid energy management, we have perfected battery optimisation to ensure a long-lasting performance. The variostring features our Battery Lifetime Optimizer (BLO), which intelligently adapts charge cycles to preserve battery health and extend its lifespan.
Thanks to precise charge control and advanced management algorithms, your batteries operate efficiently, reliably, and for the long run.
World champion for efficiency in isolated converter
High efficiency in isolated converter with >98 % and High MPPT tracking efficiency >99.8%
Automatic and efficient night stand-by for lower consumption
To save energy, when the photovoltaic voltage is low, the variotrack switches to night mode. The charger automatically wakes up when the sun starts shining and when the PV voltage goes back.
When the charger is in night mode, it consumes <1W. This feature extended battery life, reducing unnecessary consumption during periods without production.
Multi-units flexibility for more powerful systems
Scalable with multi-unit options up to 15 units with the xtender series of inverter-chargers (105kW) and 5 units with the next series (35kW).
Protection against incorrect wiring and isolation
Your safety is guaranteed, thanks to the reinforced galvanic isolation between the PV generator and battery, allowing for independent earthing of the battery and/or solar modules
The variostring integrates advanced protection features to prevent any damage caused by PV reverse polarity, overtemperature, and reverse current at night.
Tool free PV connector
Simple and trouble-free connection with SUNCLIX™ (Phoenix Contact “tool free”) PV connector
Reduces Balance of System costs (eliminates expensive wiring for parallel strings)
By allowing PV modules to be connected in long high-voltage strings, the variostring eliminates the need for bulky and expensive cabling used in parallel connections. This significantly lowers Balance of System costs, simplifies installation, and improves overall efficiency.
Distributed mini-grid function for larger systems
The minigrid is a small, autonomous electricity network that enables electricity to be produced, stored, and shared on a local scale. A centralized energy system creates the grid, and a distribution system reaches the consumers.
We have developed a series of functionalities to be the centralized system or distributed interactive systems coupled by AC.
rcc 02, full control of your installation, right at your fingertips
The rcc 02 is the perfect companion for the vario series. This compact wall-mounted remote display allows you to monitor and configure your charger with ease.
- Monitor real-time values such as battery voltage, power flows etc.
- Integrated data logging for troubleshooting and long-term performance analysis.
Configure about 200 settings of the variostring (charging curve, PV algorithm, etc.).
- Store and recall complete configuration files for easy duplication across devices or multiple systems.
Access and adjust programmable auxiliary contacts to automate functions (generator start, load shedding).
Easy monitoring via the app and the web portal
Designed to monitor your system’s data, the Studer monitoring application is perfect for obtaining information about your system at a glance.
We offer our monitoring tools completely free of charge, both the Studer monitoring app for end-users and the Studer web portal for installers, because we believe that reliable, professional, and complete monitoring should be a standard, not an option. All data is stored on European servers.
Unlock the potential of home automation integration
The potential free contacts provided by the arm 02 accessory enable certain devices to be started up according to the conditions specified in the configuration. Without the need for an external home automation system.
For more complex systems, you can use our open modbus/API “Open studer” to fully integrate the vario devices in complex and customized system architectures.
Options & accessories
Advanced battery accessories
bts 01
temperature sensor
bsp
advanced battery processor (lead-acid)
xcom CAN
communication with lithium BMS
Display, datalogger, monitoring and communication
rcc 02/03
configuration, display, datalogger
xcom LAN/GSM
remote monitoring (Portal & App)
xcom 4G
remote monitoring (Portal & App)
xcom 232i/CAN/485i
communication bridges (openstuder)
Other accessories
vario
solar charge controller
next
inverter-charger
xtender
inverter-charger
arm 02
external auxiliary contacts module
Options & accessories
Advanced battery accessories
bts 01
temperature sensor
bsp
advanced battery processor (lead-acid)
xcom CAN
communication with lithium BMS
Display, datalogger, monitoring and communication
rcc 02/03
configuration, display, datalogger
xcom LAN/GSM
remote monitoring (Portal & App)
xcom 4G
remote monitoring (Portal & App)
xcom 232i/CAN/485i
communication bridges (openstuder)
Other accessories
vario
solar charge controller
next
inverter-charger
xtender
inverter-charger
arm 02
external auxiliary contacts module
Technical specifications
variostring vs 120 high-voltage solar charger
In case of technical data change, this bloc below needs to update, it is use for mobile display of technical data
| MPPT 1/2 | 1+2 in parallel | 1+2 in series |
Solar PV
| Max. solar power recommended (@STC) | 3500 W | 7000 W | 7000 W |
| Max. current PV | 13 A | 26 A | 13 A |
| Max. solar open circuit voltage | 600 V | 600 V | 900 V |
| Min. solar functional circuit voltage | 100 V | 100 V | 200 V |
| Recommended MPP voltage | 250 – 500 V | 250 – 500 V | 500 – 700 V |
Battery charger
| Max. output current | 60 A | 120 A | 120 A |
| Nominal battery voltage (Input range) | 48 V | ||
| Operating voltage range | 38-68 V | ||
| Battery grounding possibility | battery + or battery – | ||
| Max. standby consumption | < 25 mA (1.25 W) | ||
Electronic protections
| PV reverse polarity | ✔ |
| Overtemperature | ✔ |
| Reverse current at night | ✔ |
| Galvanic isolation | ✔ |
| PV grounding possibility | PV +, PV -, floating |
| Ground fault Protection | Programmable |
General data
| Weight | 7.5 kg |
| Dimensions h/w/l [mm] | 133 / 322 / 466 mm |
| Conformity | low voltage directive (LVD) 2014/35/EU, 62109-1, electromagnetic compliance (EMC) directive 2014/30/EU, 61000-6-2, 61000-6-4 |
Ingress protection of enclosures IP20 | Mounting location indoor | Operating temperature range -20 to 55°C | Relative humidity 95 % (non condensing) | Parallel operation (separated PV arrays) up to 15 devices | Max. wire size/cable glands 70mm2/2xPG21 | Configuration with rcc 02/03, internal DIP switches for basic settings | Datalogging with rcc/xcom on SD card 1 minute resolution | Studer communication bus cable included 2 m
In case of technical data change, this bloc below needs to update, it is use for pc and tablets display of technical data
| MPPT 1/2 | 1+2 in parallel | 1+2 in series |
Solar PV
| Max. solar power recommended (@STC) | 3500 W | 7000 W | 7000 W |
| Max. current PV | 13 A | 26 A | 13 A |
| Max. solar open circuit voltage | 600 V | 600 V | 900 V |
| Min. solar functional circuit voltage | 100 V | 100 V | 200 V |
| Recommended MPP voltage | 250 – 500 V | 250 – 500 V | 500 – 700 V |
Battery charger
| Max. output current | 60 A | 120 A | 120 A |
| Nominal battery voltage (Input range) | 48 V | ||
| Operating voltage range | 38-68 V | ||
| Battery grounding possibility | battery + or battery – | ||
| Max. standby consumption | < 25 mA (1.25 W) | ||
Electronic protections
| PV reverse polarity | ✔ |
| Overtemperature | ✔ |
| Reverse current at night | ✔ |
| Galvanic isolation | ✔ |
| PV grounding possibility | PV +, PV -, floating |
| Ground fault Protection | Programmable |
General data
| Weight | 7.5 kg |
| Dimensions h/w/l [mm] | 133 / 322 / 466 mm |
| Conformity | low voltage directive (LVD) 2014/35/EU, 62109-1, electromagnetic compliance (EMC) directive 2014/30/EU, 61000-6-2, 61000-6-4 |