general overview

diagrams, descriptions

Connecting is a very large theme. Get a general overview of all connections. Read below.


dimensions, earthing, cables, tempsensor ...

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connection the ac

details below


internal solar charge controller

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with ethernet port

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Highlight Your Content

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com cables

studer nx communication bus

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general overview

system block diagram

This is the general schematic overview of the next 3. Install your next3 between the grid and the house.

The connection of the next3 charger is an important step of the installation. The next 3 is designed to be robust and is electronically protected against overloads, short-circuits, overheating, polarity reversal of the battery and polarity reversal of the PV.  Be aware of the following general guidelines: 

  • It may only be carried out by qualified professionals, aware of the rules and regulations in 
    force. The installation must always comply with the local standards.
  • The cross-sections of the cables connected to its terminals must comply with local regulations  even if indications are given in following chapters. 
  • The installation materials such as cables, connectors, distribution boxes, fuses, etc. must be 
    adapted and must be conform to the applicable laws and regulations, specially about fire 
  • All cables in use should be isolated with PVC, TFE, PTFE, FEP, neoprene or polyimide. Make sure  that connections are correctly tightened and that each wire is connected at the right place. 

    The next3 falls within protection class I. It has a PE connection terminal. It is mandatory that a protective earth is connected to the AC-Source and/or AC-Loads PE terminals. An additional protective earth is located at the bottom of the unit. 

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connections overview

The connection compartment of the next3 must remain permanently closed while the device is operating.
Before opening, check that all voltage sources (AC, battery and PV) have been disconnected or switched off and wait for at least 2 minutes before opening the equipment. It is imperative to close the protection cover on the connection terminals after each servicing. 

Before connecting or disconnecting the entry or exit cables AC-Source, AC-Loads and AC- Flex, the installer must be sure that there is no voltage present in the cables OR on the terminals. 

ny unused cable entry on the device must be sealed to prevent any intrusion. An intrusion of small animals in the unit may cause serious damages not covered by the warranty. 

Open the connection compartment by removing front cover.

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Thightening torques

The tightening torque of different connection points should be checked regularly, especially in installations exposed to strong vibrations (mobile systems, vehicles, boats, ...). The table below states the recommended tightening torques for each connection.

An annual check of all the connection tightness is recommended.
In mobile installations, the connection tightness should be checked more often. 


max permissible cable cross-sections summary

The maximum permissible cable cross-section for each connection is defined by the size of the corresponding cable gland, which is indicated in the below table.

connecting the battery

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next3 is a device wich DC (battery) connection is to be connected EXCLUSIVELY to a 48v battery

Due to high power of the next3, the battery cables are separated in two entries in parallel to have a more convenient handling. The recommended battery cable size is 70mm2 for a total of 140mm2 with two cables in parallel. The maximal size is 95mm2 for a total of 190mm2 section.
Battery cables must also be as short as possible, and the cross-section must conform with the applicable regulations and standards. Sufficiently tighten the clamps on the "battery" inputs. 

ATTENTION! Battery cables must always be protected by one of the following measures: Have a protection and disconnection device (fuse, circuit breaker) on each pole or  only on the pole not connected to earth.
The protection device must be rated according to the cable cross-section but must not exceed 1.25 x next3 maximum current. It will be mounted as close as possible to the 
battery. The maximum current is given with 16000/48=333Adc with factor: 333x1.25=416Adc 

Each next3 is connected directly to the battery through its own protective device (fuse or circuit breaker) and disconnection device. It should never be connected to the output of a DC voltage regulator like solar regulator, without having the battery as a buffer.
All other consumers or sources are connected directly to the battery by their own protective and disconnection devices. 

Battery cable cross-section, DC protective and disconnection devices .

The battery cables must also be as short as possible. Recommended section for the nx3 battery cables is 2x70mm2 and a 400Adc protection. The recommended cable cross-sections are valid for lengths less than 3 m. Beyond this length, it is strongly recommended to oversize the battery cables (possible up to 2x95mm2 for cables connected to next3 battery poles) and consider the voltage drop in the cables. 

For safety reasons, we recommend an annual check on the tightening and corrosion of all connections. In mobile installations, the tightening of the connections should be checked even more frequently. For lead acid batteries, an individual measurement of each cell is recommended. Any divergent values can be a sign of problem.  To avoid any further loss and protection redundancy, the next3 does not have an internal fuse. 
The battery cables must be protected by one of the following measures:
- protection device (fuse) and disconnection device at each pole
- protection device (fuse) and disconnection device on the pole not connected to the earth In all cases check local regulation and normative. 

Start the connection on the next3 side first, without any voltage. Keep battery poles away/ protected to prevent any unwanted contact with conducting parts. 

next3 side connection 
Insert the cable glands supplied on the battery cable before tightening the cable lugs. Crimp the cable lugs and fasten the cable gland on the device. Repeat this for all battery cables. Fix the battery cables to the appropriate connections "+ Battery" and "- Battery". The M8 screws must be very well tightened (10Nm). 
battery-side connection 
Prepare the batteries for connection: appropriate battery clamps, protection device, cables in good conditions with correctly fitted clamps.  Fasten the negative cable on to the negative pole (-) of the battery and the positive cable on the open protection device.
The cable lugs must be carefully fixed and tightened sufficiently to guarantee minimum loss. Insufficient tightening may cause dangerous heating at the connection point. 

During the first start of the unit, it is necessary to check that the parameter values of the next3 are consistent with the recommendations of the battery manufacturer. Non- conforming values may be dangerous and/or seriously damage the batteries.
See the chapter about programming and set the proper values at initial commissioning (with wizard on nx-interface). 


One of the two battery conductors can be earthed. This may be either the positive or the negative pole as the battery is isolated from the other potentials (PV, AC). In all cases, the installation must be conform to the local regulations and usage or specific standards associated with the application. 

In case of earthing, the earthing conductor cross-section must at least be equivalent to the cross- section of the battery conductor. The earthing of the equipment must also adhere to these regulations. For this case, use the additional earthing screws, which are located at the bottom of the device under the AC cabling glands. 

All the other earthing systems (earthing by means of a protection device, impedance, without earthing or earthed at battery positive pole) require the whole battery circuit to be protected against electric shocks.  Any accidental contact with the conductive parts of the battery circuit is to be avoided by providing a Class II protection level. 
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connecting to lithium batteries

Most lithium batteries require communication between the battery's BMS and the rest of the system to properly manage charge and discharge. In most cases, lithium batteries use a CAN bus (physical layer), but must have specific protocols established to communicate. The next3 has several protocols for battery management and the type of battery is set with the configuration wizard and then the right protocol and baud rate is used.

See the Studer-Innotec website for the latest list of compatible batteries, brand and model, and the next3 software updates to have the latest communication protocol.Pay attention to the pin order (CANH, CANL, GND) on the connector, see carefully the instructions of the BMS manufacturer. An appendix on the different lithium batteries is available.

For a point-to-point connection, the bus termination must be set to T (Terminated). If the device is in the middle of a daisy chain, the termination is set to O (Open).In general, the next3 is connected point-to-point to the BMS and the termination should be set to T.
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Most communication devices have a specific connector and a specific signal position on the wires. There is no standard. Even with an RJ-45 connector, the pining is sometimes variable.The cable is provided by the manufacturer or must be made by the installer respecting the signals of the communication line (GND, CAN-H, CAN-L).

As an example, here is the pin assignment according to CIA-303-1 Which are to be connected with the screw connector.

configurations with battery type

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Lead-acid batteries do not require any special programming, except for the usual precautions and configuration during the configuration wizard.

The next3 should not be located directly above vented lead-acid batteries, nor in a cabinet with them, due to the corrosive gas.

Be careful not to use lead-acid batteries at more than 50% DOD to ensure a reasonable life span. 
The operating voltages of lead-acid batteries vary with temperature.depending on the temperature. 

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battery temperature sensor connection (nx-tempsensor)

A temperature sensor is available to correct the battery voltage and to guarantee an optimaloptimal charge depending on the battery temperature. The temperature range of the sensor is between -30°C and55°C. The default temperature compensation forbatteries when a sensor is connected is - 3mV/°C/cell with respect to 25°C. For a 48V battery, this represents 72mV/°C. See the configuration section of this manual.  For the modification of the temperature coefficients nx-tempSensor is supplied with a 10m cable and the appropriate male connector next to it. The connection has no polarity and can be made in either direction without preference. The sensor should be placed as close as possible to the battery.

The temperature sensor is automatically recognized, and the correction of the voltage thresholds applied immediately in case of a non-communicating battery. If a communicating battery is used, the temperature measured by this sensor is not taken into account because the temperature is directly given by the BMS. The temperature of the nx-tempSensor is recorded in the datalog.

The operating voltages for lead batteries vary depending on the temperature. A temperature sensor is available to correct the battery voltage and guarantee an optimum charge in function of battery temperature.

The temperature range of the sensor is from -30°C to 55°C. The 

default temperature compensation for lead acid batteries when a sensor is plugged is -3mV/°C/cell compared to 25°C. For a 48V battery this is 72mV/°C. See the configuration section of this manual for modification of the temperature coefficients. The temperature sensor nx-tempSensor is supplied with a 10m cable and the proper male connector beside. The connection has no polarity and can be done in one or the other direction without preference. The sensor should be placed as close as possible of the battery 

The temperature sensor is automatically recognized, and the
correction of the voltage thresholds applied immediately in case of non-communicating battery. If a communicating battery is used the temperature measures by this sensor is not taken into account as the temperature is directly given by the BMS. The nx-tempSensor temperature is recorded in the datalog. 

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Can Connection: battery with communication bms

The next3 uses a CAN Bus to communicate with the BMS (Battery Monitoring System) of a lithium battery. Lithium batteries are more complex to handle compared to lead acid batteries. A BMS is responsible of cell monitoring and battery safety. The BMS knows the status of each cell, and it computes maximum charging/discharging currents and maximum/minimum target voltages. These values must be respected when the installation is working and BMS communicates to inverter/chargers the proper setpoints for proper operation.  The next3 has several CAN protocols implemented for communication with different battery management.
These protocols are compatible with specific batteries, as listed in list below: 
  • AutarcTech 
  • BlueNova 
  • BMZ 
  • BYD 
  • Cegasa 
  • Cosun 
  • Discover 
  • FreedomWon 
  • IPS 
  • Pallas 
  • PowerTech 
  • Pylontech 
  • Soltaro 
  • SuperB (with BCI) 
  • TesVolt 
  • Weco  
  • •...  

See the Studer-Innotec website for the up-to-date list of compatible batteries, brand and models 
and updates of the next3 software to have the latest communication protocol.
Beware of the pinning order (CANH, CANL, GND) on the connector, see instruction of the BMS manufacturer carefully. An appendix about various lithim batteries is available. 
For a point-to-point connection, the bus termination should be set to T (Terminated). If the device is in the middle of a daisy chain, the termination is set to O (Open).
Generally, the next3 is connected point to point to the BMS and the termination should be on T. 

connecting the grid (AC)

connecting the alternative current

warning: Dangerous AC may be present on the connection terminals. Make sure that the inverter is deactivated and that there is no AC or DC voltage present on the AC terminals before proceeding with the connection. 

On the next3 model, remove the cover plate by unscrewing the two screws to access the AC terminals and protective earth. The connections inside are shown on the figure below.
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There are 3 AC connections: 
  • AC-Source : connection for the main AC source. A grid or a generator. This input has double security relays for disconnection according to safety and grid code requirements like VDE-0126 and others. In case of grid connection, always connect the grid to AC-Source. 
    In offgrid, a single-phase source may be used and connected to the L1 of the AC-source. For example, for a small single phase genset as a backup.
  • AC-Loads : connection for the loads, that are supplied by the inverter. The 230 V and 400V consumers must be connected on the "AC-Loads" connection terminals with the wire cross- section conforming to the standards regarding the rated current at the next3 output. 
  • AC-Flex : this is a configurable connection to be connected to loads or to a genset. The choice of configuration is done at the setup of the system during the Wizard procedure. The AC-Flex configuration is fixed and cannot be changed anymore in operation for security reasons. 
    On models without transfer (nx3-16000-48 and -s) there is no AC-Source and no AC-Flex connections.  
Refer to the general schematics (block diagram) at the beginning of this chapter for a better understanding.
The next3 terminals are marked in the following way: 
N = neutral
L = lines (L1, L2, L3) 
= protective earth (connected to the enclosure of the device).

example of connection for ac loads

Information: Insulation tests 
At commissioning of an electrical system, insulations tests are performed on the wiring (in some countries, depending on local regulation). It is performed applying high voltages on the cables and measuring the leakage current. This must be done without the next3 in the loop. Over-voltage surge protections included in the next3 will invalidate the tests. 
Insulation between circuits and the ground is tested in factory for every next3 unit manufactured according to the device IEC/EN 62109 and IEC/EN 62477 safety standards. 
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Sizing of ac protective devices

The source must be connected to the input terminals marked "AC-Source" with sufficient wire cross- section, depending on the power output of the source, and protected by a protection device of the appropriate rating. In any case it must be  maximum 80A per nx3

For people safety, we recommend using residual current devices (RCD) for loads at the output of the nx3. Take care of the earthing and neutral system for proper operation of the RCD. In any case, AC distribution must comply to the local standards and regulations, and generally, be realised through a distribution panel in an enclosure.  For cables protection, no downstream protective device is formally required if cross-sections of cable used for distribution satisfy to regulatory requirements for the largest rated output current listed on the nameplate of the next3. The next3 is protected against overload and short-circuit and will stop in those cases. When connected to a source, the upstream protection must stop short-circuits currents from the grid/genset. 

Due to the source assistance function (Smart-Boost), the current at the output of the device may be higher than the rated current of the inverter. It is the sum of the current supplied by the additional source and the current supplied by the inverter. In this case, the dimensioning of the output cables will be carried out by adding the current indicated on the protection device located on the upstream of the unit, to the nominal current of the inverter. 

If circuit brakers (CB) are installed at the output, we recommend B c urve devices. They will be sized at maximum to the highest value  listed on the unit’s nameplate or by the addition of the first value plus  the value of the input protective device. (i.e. inverter current + input  current). As example, if the AC Source current is 50Aac per phase  and knowing that the current of the inverter is (16000/230/3)=23Aac per phase, the total current on the output would be 73Aac per phase.  In any case it must be chosen according to the cable size downstream. 

If the source assistance function (Smart-Boost) is not used; the size of the protection device for the AC-loads output will be established at a maximum value equal to the rated current of the inverter, or at the maximum value of the protection device at the input if that one exceeds the rated current of the inverter.  If the AC-source is not used the protective device will be sized equal or smaller than the smaller value indicated on the nameplate. 

The next3 is intended to be supplied by alternative voltage sources such as the grid or a generator. Check that the rated voltage of the source corresponds to the rated voltage of the next3 model specified on the nameplate on the side of the next3. 

ac neutral and earthing system

The next3 is a unit with protection class I, which is intended for cabling in a grid type TT, TN-S or TNC-S. Its metal case must be earthed. The earthing of the neutral conductor is carried out at a sole installation point, upstream of the RCD circuit breaker (in domestic application, generally type A, 30 mAac).  The neutral insulation to the earth is checked by the device and errors will be raised by the next3 if the measurements doesn’t correspond to the settings of the device.  The next3 case and/or the PE connector, depending on the local installation rules, have to be connected to earth. The PE cross section must be as big as the cross section of the line or neutral conductor, but the minimum cross section must be at least 10mm2.  PE = protective earth (connected to the enclosure of the equipment). 

In any case, the protective earth must be connected in accordance with local standards and regulations in force. The protective earth of the equipment must be connected at least to the protective earths of all the Class I equipment after and before the next3 (equipotential connection). The information, notes, recommendations, and diagrams reported in this manual are examples and must in any case be adapted to local installation rules. The installer is responsible for the conformity of the installation with the local standards in force. 

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An additional earthing terminal is present under the AC-cables glands at the bottom of the unit. It can be used instead of a connection on the input terminals of the device, particularly when cable cross-sections used at the output do not allow the use of a five-wire cable (lines L1 L2 L3, earth and neutral) through the conduit glands of the connection cables of the input and output (AC-SOURCE, AC-LOADS and AC-FLEX), or when the earthing of one of the poles of the battery. PE required using same or greater cross-sections than the battery cable when the battery is grounded. 

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Stationary installation and neutral continuity

In a stationary installation where the neutral is connected to the earth at a single installation point upstream of the next3, it is permissible to carry out a connection of the neutrals to preserve an unchanged earthing system downstream, independent of the operating mode of the next3. This is called “Solid Neutral”. 

That can also be performed with the proper programming of the unit, controlling the internal earthing relay, but it may not be accepted for security reasons. Please check your local installation rules.  Example of solid neutral connection inside of the connexion box.  Safety is guaranteed by the equipotential bonding and by any RCD circuit breakers placed downstream.

This connexion can be done inside of the next3 with an internal relay and the proper programming. See the earthing relay configuration in the system configuration. 
This solid neutral connection is not permitted if a socket is installed upstream of the next3 (typically in mobile application). 
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Mobile installation or installation connected to the grid via plug connector 

When the input of the device is connected directly to the grid via a plug, the plug must remain accessible. The connection (link) between the neutrals upstream and downstream of the next3 is not permitted in this configuration. 
In the absence of voltage at the input, the neutral and live are interrupted, thereby guaranteeing complete isolation and protection of the cabling upstream of the next3.

The earthing system downstream of the next3 is determined by the upstream earthing system when the grid is present. In the absence of the grid, the earthing system downstream of the inverter is in isolated mode. An automatic connection with an internal relay can be programmed with settings. 

This connection type guarantees the optimal continuity for supplying the next3 loads. The first isolation fault will not lead to an interruption in the supply. If the installation requires the use of a permanent isolation controller this would have to be de- activated when the TT network is present at the next3 input. 

All sockets and protection class I devices connected downstream of the next3 must be properly connected to the earth (earthed socket). The cabling rules above remain valid, including in installations, in all cases where the next3 input is connected to the grid via a plug connector. 

next system without transfer

On models without transfer (nx3-16000-48 and -s) there is no AC-Source and no AC-Flex connections. These models do not have programmable earthing relay either. Thus, user must guarantee complete isolation and protection of the system. In such installation it is recommended to bond directly the neutral to the earth at one point in the system. 

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connectig the photovltaic generator

The next3 has an internal solar charge controller made of two independent MPPTs. Each MPPT can support up to 22Adc of photovoltaic (PV) current in operation. For this reason, each MPPT has 2 inputs and up to 4 strings can be connected to the device. The two inputs of the top (MPPT1) are connected internally, as well as the two at the bottom (MPPT2). The rated current of the PV generator can be higher as the next3 limits with electronic control the maximum taken from the generator in any case. In any case the maximum short-circuit (Isc) current is 27Adc. 

The next3 solar input is intended to be connected exclusively to a source like a photovoltaic generator, excluding any other energy source. 

The next3 is designed for PV generators supplying up to 900Vdc. This voltage is dangerous for human beings.
During the installation or the maintenance of the system, it is mandatory to make sure that no dangerous voltage may surge in the system. The disconnection device must be open and secured against any accidental reclosing.