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Smart BatteryProtect 12/24V

3. Installation and wiring examples

In this section:

3.1. Precautions and installation notes

There are a few basic things to keep in mind when installing a Smart BatteryProtect:

  1. The Smart BatteryProtect must be installed in a well-ventilated area and preferably close (max 50 cm) to the battery (but, due to possible corrosive gasses not above the battery!).

  2. Choose the correct cable size and length to match the load. Voltage drop over a long or undersized cable between the battery plus and the SBP may result in a short circuit alarm when starting-up the load, or unexpected shutdown. You can also find more information on selecting the right cable size and its protection in our book Wiring Unlimited.

  3. A properly sized fuse must be inserted according to local regulations in the cable between the battery and the SBP.

  4. Pay attention to the correct orientation. The SBP is designed to allow current to flow from IN (battery) to OUT (load) terminals only. Reverse currents from OUT to IN terminals are strictly forbidden and will damage the device. If you wish to use the SBP as a disconnection for a charge source, you must orient the unit in the system so that the current is flowing in the intended direction, IN to OUT.

  5. The short circuit protection of the SBP will be activated if you try to directly connect loads with capacitors, for example inverters or inverter/chargers, on their DC inputs. For that use case, please use the SBP to control the remote on/off control on the inverter, instead of disconnecting the higher power DC line. See also the warning on the next page.

  6. Use the supplied 1,5mm2 wire for the GND connection, which should be connected directly to the battery negative terminal (or the chassis of a vehicle). No other equipment should be connected to this wire. Note that the GND cable must be protected accordingly. A 300mA fuse is sufficient.

  7. The pin assignment of the connectors are printed either on the front or on the side of the housing.

  8. The SBP automatically detects the system voltage once only during initial power up. The selected voltage (12 or 24 V) is stored, and further automatic detection is disabled. See "d" in the programming table for how to reset it when re-using the SBP in a different installation or use Bluetooth.

  9. Do not connect the load output until the SBP has been fully programmed.

  10. A remote on/off switch can be connected between Remote H and Remote L. Alternatively, terminal H can be switched high (to battery positive), or terminal L can be switched low (to battery negative).

  11. A buzzer, LED or relay can be connected between the alarm output terminal and the battery positive. Maximum load on the alarm output: 50mA (short circuit proof).

3.2. Warning when connecting inverters and inverters/chargers


Under no circumstances is it permitted to connect inverters or inverter/chargers to a SBP via their DC inputs, a reverse current may flow that damages the SBP. In case you want to control an inverter or inverter/charger via a SBP, you must use the SBP to control the inverter or inverter/charger via its remote port. See example below. Note that the image shown below is an example for all BatteryProtect models including the smart models.


Left image: Inverter DC input connected via a BatteryProtect - strictly forbidden

Right image: Inverter controlled by its remote port via BatteryProtect

3.3. Wiring examples

This section contains various wiring examples to show all the possibilities of wiring.

3.3.1. Smart BatteryProtect in a simple system

The example below shows a Smart BatteryProtect with the wire loop (default) between L and H of the remote terminal. When the wire loop is removed, the SBP disconnects the load after 90 seconds.

However, if the wire loop remains plugged in and the battery voltage drops below the programmed value for under voltage shutdown (see section Programming), the SBP disconnects the load after 90 seconds automatically.


Smart BatteryProtect in a simple system with wire loop between L and H input (factory default)

The same example below. This time the switch is wired between battery positive and the H input of the remote terminal.

When switched off, the H input becomes low. The load is disconnected after 90 seconds. When the switch is turned on again, the H input becomes high and the load is turned on with a delay of 30 seconds.

This works in the same way between battery minus and the L input of the remote terminal.


Switch wired between battery positive and H input of the remote terminal

3.3.2. Smart BatteryProtect remote on/off switch

The below example shows a Smart BatteryProtect in a simple system with a remote on/off switch wired to the remote terminals.

This switch can be used, for example, to turn the system remotely on and off. The power consumption of the Smart BatteryProtect is negligible at less than 1mA when switched off (check the Specifications chapter).


Smart BatteryProtect with remote on/off switch

3.3.3. Smart BatteryProtect in a lithium battery system with external BMS

The image below shows a Smart BatteryProtect in a lithium battery system with external BMS. The external BMS (Victron Lynx Smart BMS in this example) has an ATD (allowed to discharge) and ATC (allowed to charge) output. Designed as a dry contact, ATD and ATC function as a switch that directly controls the SBP via its remote terminal.

For this, the Smart BatteryProtect must be programmed to Li-ion mode.

The dry contact is wired between the L and H connectors of the remote terminal.

If, for example, ATD opens in the event of a lithium battery cell undervoltage, the SBP will immediately disconnect the load without delay.

The SBP will remain disengaged for 30 seconds, even if ATD closes within this period. After this 30 seconds, it responds immediately and connects the load to the battery.

Please note that the under voltage thresholds and alarm output of the SBP are inactive in this mode.


If you have a lithium battery with internal BMS (so-called drop-ins) that does not have an output for controlling loads or chargers, the SBP must be programmed in mode A or B. Mode C is not applicable in this case.


Smart BatteryProtect in Li-ion mode controlled by ATD from a Lynx Smart BMS

3.3.4. Smart BatteryProtect in a lithium system with external BMS and load disconnect output

This wiring example shows a Smart BatteryProtect wired into a lithium system that is controlled by an external BMS (Victron smallBMS with pre-alarm). This BMS has a load and a charge disconnect output that can be wired directly to the Smart BatteryProtect H input of the remote terminal.

As with the previous example, it is necessary to program the SBP into Li-ion mode (see chapter Programming).

If, for example, the smallBMS triggers the pre-alarm because of an imminent low cell voltage, the load output becomes free floating (normally high) when there is an actual low cell voltage and the SBP will disconnect the load and remains off for 30 seconds, even if it receives a restart signal (H becomes high again) within this period. After 30 seconds, it responds immediately to a restart signal.


If the system has been switched off due to low cell voltage, the SBP will remain off for 30 seconds, even if it receives a restart signal within this period (which is most likely the case if no other loads are connected to the battery). After 3 attempts, the SBP will remain off until the battery voltage has risen above 13V (or 26V for a 24V system) for at least 30 seconds (which is an indication that the battery is being recharged).


Smart BatteryProtect uses the load disconnect of a smallBMS

3.3.5. Two Smart BatteryProtects for load and charger control

It is also possible to have several Smart BatteryProtect in one system, for example, to control chargers and loads at the same time.

If the BMS signals a cell undervoltage, the SBP responsible for the load will disconnect the load from the battery to protect the battery from further discharge.

If the BMS signals a cell overvoltage or too low temperature to charge the lithium battery, the SBP will disconnect the charger from the battery immediately.

Please also note the correct connection of the SBPs: always follow the current flow from IN to OUT. The positive terminal of the charger goes to the IN input of the SBP.


Two Smart BatteryProtects take control of a charger and a load circuit

3.3.6. Smart BatteryProtect Alarm output wiring

The alarm output can be wired e.g. to an LED, a buzzer or a relay. For this, the Smart BatteryProtect must be programmed in the respective mode because of slight differences in the behavior. See also the section Operation modes for more details.

Make sure that the LED, buzzer and relay match the system voltage.


Wiring an LED, Buzzer or Relay to the Smart BatteryProtect output