Smart BatteryProtect disconnects the loads or does not switch them on

• The battery positive must be connected to the IN terminal — through a fuse.
• The SBP needs a separate ground wire: the supplied 1.5 mm² cable from the GND terminal straight to the battery negative (or vehicle chassis). Do not connect any other equipment to it. The GND wire must be protected — a 300 mA fuse is sufficient.
• Operating voltage range: 6–35 V (12/24 V version) or 24–70 V (48 V version).
• Mount the SBP in a well-ventilated place, preferably close to the battery (up to 50 cm), but not above it — because of possible corrosive gases.

From the factory, the L and H pins on the remote connector are linked by a bridge. Removing it immediately disconnects the loads. You can use a switch instead of the bridge:

• between H and L,
• between battery positive and H pin (H in high state — loads on),
• between battery negative and L pin.

The SBP switches the loads on 1 second after the remote circuit is closed and disconnects them immediately when it is opened (in Li-ion mode, a further 30-second delay also applies — step 4). Programming by the PROG–GND method requires the bridge to be removed from the remote connector — after programming, check that it has been put back.

When the voltage falls below the switch-off threshold, the alarm output is activated after 12 seconds (buzzer, LED or relay), and after 90 seconds the SBP disconnects the loads — it then shows E3. Starting the engine does not therefore trigger an alarm. A quick response during this time — reducing the load or starting charging — can prevent disconnection. The loads return when the voltage rises above the restart threshold — with a 30-second delay.

• Will not switch on after charging — compare the battery voltage with the set restart threshold. In some settings it is high (for example 13.8 V in setting 4 for 12 V).
• Disconnects even though the battery is charged — check the cable between battery positive and the SBP. According to the manual, voltage drop on a long or too-thin cable can trigger a short-circuit alarm when a load starts or an unexpected shutdown.
• E3 repeats — the manual instructs you to switch off or disconnect the loads, charge the battery and check whether the charging system and battery are functioning correctly.

You set the thresholds in VictronConnect (including custom ones) or by the PROG–GND method: the display cycles through settings 0–9, and releasing the button selects the setting. The factory values (10.5 V and 12 V for 12 V, 42 V and 48 V for 48 V) correspond to setting 0.

In Li-ion mode (C), the voltage thresholds and alarm output are inactive — the loads are disconnected by the signal from the BMS instead (step 4).

Choose Li-ion mode (C) only when the BMS has a load disconnect or charge disconnect output. Batteries with a built-in BMS (so-called drop-in) usually do not have it — for those, the manual says to set mode A or B. In Li-ion mode, the SBP voltage thresholds do not operate.

• Connection — the BMS load disconnect (or charge disconnect) output is connected to the H pin of the remote connector. A potential-free contact, for example ATD in Lynx Smart BMS, is connected between L and H.
• Disconnection — when the BMS output changes from high to “floating” (or the ATD contact opens), the SBP immediately disconnects the loads.
• 30-second delay — after disconnection, the SBP will not switch on for 30 seconds, even if it receives permission during that time; afterwards it responds immediately. In Li-ion mode, a dot flashing every 2 seconds means the output is in the process of switching on.
• E7 — if the BMS disconnects and reconnects the SBP three times in a row (typical when switching off due to low cell voltage, especially when no other loads are connected to the battery), the SBP is switched off. It will switch on when the voltage has been above 13 V (12 V system), 26 V (24 V) or 52 V (48 V) for at least 30 seconds — this indicates that the battery is charging. Check the BMS codes and history, charge the battery, and check the wiring between the BMS and the SBP remote connector.

In the 48 V version manual, the E7 description in the appendix gives thresholds of 13 V and 26 V (as for 12/24 V), while sections 3 and 4 of the same manual give 52 V. Has the BMS also disconnected charging? See “BMS disconnected charging”.

E1 indicates the short-circuit protection has tripped — due to a short circuit, overload, or excessive inrush current. SBP tries to switch the loads on every 5 seconds; after two attempts it shows E1. The most common case in the manual: an inverter or inverter/charger connected directly to the SBP output — the capacitors on its DC input trigger the protection. Control such a load via its remote port, not by disconnecting the power cable.

• Check whether there is a short circuit in the load circuit.
• Check whether the load current does not exceed the SBP’s capacity.
• Check for loose connections and cable cross-section — voltage drop on the battery cable can also trigger the short-circuit alarm (step 3).

P2 warns that the internal temperature is close to the limit — the manual requires urgent action before the SBP disconnects the loads (E2). What to check:

• whether the load current does not exceed the SBP’s capacity (table in step 5);
• whether the connections are not loose or high-resistance, and whether the cable cross-section is correct;
• whether the SBP is installed in a hot place or within the reach of heat radiation — move it to a cooler place or add active cooling.

The SBP delivers full current at temperatures from −40 to 40 °C; at 50 °C — up to 60% of the rated current.

In an overvoltage situation, the SBP disconnects the loads immediately. In the 12/24 V version, the threshold is 16 V (12 V system) and 32 V (24 V) according to sections 4.1 and 7.1, and 16.3 V and 32.6 V according to section 2; in the 48 V version — 64 V. The manual says to check the settings of all chargers (especially the system voltage and charge voltages), the charging system operation, and the system voltage set in the SBP.

The SBP 12/24 V detects the system voltage only once — at first power-up — and stores it. After moving it to another installation, you must detect it again: with position “d” in PROG–GND programming or in VictronConnect, where you can check in the settings whether the detected battery voltage matches the system voltage. If the SBP has stored 12 V in a 24 V installation, its normal voltage exceeds the 16 V overvoltage threshold.

The manual for the 48 V version also refers to position “d”, but this position is not in its programming table.

The SBP works in only one direction — current to the load or current from the charger, never both at once, and always from IN to OUT. When the voltage on OUT is higher than on IN, uncontrolled reverse current flows, which can permanently damage the SBP. Therefore never use the SBP to charge one battery from another.

• Check the mounting direction — current must flow from IN to OUT.
• Check whether a charging source is not mistakenly connected to the OUT circuit.
• If the SBP disconnects a charger, the charger positive goes to the IN terminal, and no loads may be connected to the IN circuit. To control a charger and loads at the same time, two separate SBPs are used.

• Bluetooth disabled in the app — you can re-enable it only with the PROG–GND method: position “F” enables Bluetooth, “h” disables it.
• Unknown PIN — position “P” resets the PIN; then delete the SBP pairing data from previously paired devices.
• PROG–GND method — battery positive on IN, ground wire on GND, OUT terminal not yet connected, jumper from remote removed. Short PROG to GND (preferably with a button): the display steps through the settings, releasing selects the position, and the SBP confirms it twice. Another short selects the operating mode (A, b, C); the same table also includes special positions (d, F, h, P).
• The manual recommends not connecting the load output until the SBP is fully programmed.

Other connection problems: “VictronConnect does not connect via Bluetooth”.