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BatteryProtect 48V 100A

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 BatteryProtect:

  1. The 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 BP 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 BP.

  4. Pay attention to the correct orientation. The BP 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 BP 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 BP 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 BP 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 BP automatically detects the system voltage once only during initial power up. See "d" in the programming table for how to reset it when re-using the BP in a different installation.

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

  10. A remote on/off switch can be connected between both pins on the 2-pin remote terminal. Alternatively, the terminal labelled REMOTE can be switched high (to battery positive).

  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 BP via their DC inputs, a reverse current may flow that damages the BP. In case you want to control an inverter or inverter/charger via a BP, you must use the BP 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. BatteryProtect in a simple system

The example below shows a BatteryProtect with the wire loop (default) between the two-pin remote terminal. When the wire loop is removed, the BP 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 BP disconnects the load after 90 seconds automatically.


BatteryProtect in a simple system with a wire loop between the two pins of the remote terminal connector (factory default)

The same example below. This time the switch is wired between battery positive and the pin labelled REMOTE of the remote terminal.

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


Switch wired between battery positive and REMOTE pin of the remote terminal

3.3.2. BatteryProtect remote on/off switch

The below example shows a 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 BatteryProtect is negligible at less than 1mA when switched off (check the Specifications chapter).


BatteryProtect with remote on/off switch

3.3.3. BatteryProtect in a lithium battery system with external BMS

The image below shows a 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 BP via its remote terminal.

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

The dry contact is wired between the two pins of the remote terminal connector.

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

The BP 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 BP 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 BP must be programmed in mode A or B. Mode C is not applicable in this case.


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

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

This wiring example shows a 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 BatteryProtect pin labelled REMOTE of the remote terminal connector.

As with the previous example, it is necessary to program the BP 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 BP will disconnect the load and remains off for 30 seconds, even if it receives a restart signal (the REMOTE pin 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 BP 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 reclosing attempts, the BP will remain off until the battery voltage has risen above 52V for at least 30 seconds (which is an indication that the battery is being recharged).


BatteryProtect uses the load disconnect of a smallBMS

3.3.5. Two BatteryProtects for load and charger control

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

If the BMS signals a cell undervoltage, the BP 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 BP will disconnect the charger from the battery immediately.

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


Two BatteryProtects take control of a charger and a load circuit

3.3.6. BatteryProtect Alarm output wiring

The alarm output can be wired e.g. to an LED, a buzzer or a relay. For this, the 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 BatteryProtect output