3. Installation
3.1. Important warning
Warning
Lithium batteries are expensive and can be damaged due to over discharge or over charge.
The shutdown due to low cell voltage by the BMS should always be used as a last resort to be on the safe side at all times. We recommend not letting it get that far in the first place and instead either shutting down the system automatically after a defined state of charge (this can be done with a BMV whose relay can control the remote on/off port of the BMS via an adjustable SoC value) so that there is always enough reserve capacity in the battery, or to use the remote on/off function of the BMS as a system on/off switch.
Damage due to over discharge can occur if small loads (such as: alarm systems, relays, standby current of certain loads, back current drain of battery chargers or charge regulators) slowly discharge the battery when the system is not in use.
In case of any doubt about possible residual current draw, isolate the battery by opening the battery switch, pulling the battery fuse(s) or disconnecting the battery plus when the system is not in use.
A residual discharge current is especially dangerous if the system has been discharged completely and a low cell voltage shutdown has occurred. After shutdown due to low cell voltage, a capacity reserve of approximately 1Ah per 100Ah battery capacity is left in the battery. The battery will be damaged if the remaining capacity reserve is drawn from the battery, for example, a residual current of just 10mA can damage a 200Ah battery if the system is left discharged for more than 8 days.
Immediate action (recharge the battery) is required if a low cell voltage disconnect has occurred.
3.2. Things to consider
3.2.1. Controlling DC loads via Load disconnect
DC loads must be switched off or disconnected if there is a risk of cell undervoltage in order to prevent deep discharge. The Load disconnect output of the smallBMS can be used for this purpose.
The Load disconnect output is normally high (equal to battery voltage) and becomes free floating (= open circuit) in case of imminent cell undervoltage.
DC loads with a remote on/off terminal that switches the load on when the terminal is pulled high (to battery plus) and switches it off when the terminal is left free floating can be controlled directly with the Load disconnect output. See Appendix A for a list of Victron products with this behavior.
For DC loads with a remote on/off terminal that switches the load on when the terminal is pulled low (to battery minus) and switches it off when the terminal is left free floating, the Inverting remote on-off cable can be used. See Appendix A.
3.2.2. Controlling DC loads with a BatteryProtect
A BatteryProtect will disconnect the load when:
The input voltage (= battery voltage) has fallen below a preset value (adjustable in BatteryProtect) or when
the remote on/off terminal is pulled low. The smallBMS can be used to control the remote on/off terminal of a BatteryProtect.
3.2.3. Controlling a battery charger via Charge disconnect
Battery chargers must interrupt the charging process in case of imminent cell overvoltage or low/high temperature of the cells. The Charge disconnect output of the smallBMS can be used for this purpose.
The Charge disconnect output is normally high (equal to battery voltage) and switches to open circuit state in case of imminent cell overvoltage or low/high temperature.
Battery chargers with a remote on/off terminal that activates the charger when the terminal is pulled high (to battery plus) and deactivates when the terminal is left free floating can be controlled directly with the Charge disconnect output. See the Appendix A [11] for a list of Victron products with this behavior.
Alternatively, a Cyrix-Li-Charge can be used. The Cyrix-Li-Charge is a unidirectional battery combiner that inserts in between a battery charger and the lithium battery. It will engage only when charge voltage from a battery charger is present on its charge-side terminal. A control terminal connects to the Charge disconnect of the smallBMS.
3.2.4. Battery
In case of several batteries in parallel and or series configuration, the two M8 circular connector cord sets of each battery should be connected in series (daisy chained). Connect the two remaining cords to the BMS.
Be sure to read and follow the installation instructions in the Lithium Battery Smart manual.
3.3. System examples
3.3.1. smallBMS with SmartSolar Charger and a BatteryProtect for DC loads
The below system example shows a small DC off-grid system. The main components are:
The Charge disconnect output controls a SmartSolar Charger via a VE.Direct non inverting remote on/off cable (not necessary with larger MPPTs that have a remote on/off port). In the event of low/high temperature or cell overvoltage, the solar charger will stop charging.
DC loads are controlled via a Smart BatteryProtect. Its remote H input connects to the Load disconnect output of the smallBMS. In the event of a low cell voltage, the Load disconnect output and as a result the remote H input of the Smart BatteryProtect becomes free-floating and disconnects the DC load to prevent further battery discharge.
A remote on/off switch wired between the battery positive busbar and the remote H input of the smallBMS can be used to switch DC loads and chargers off, additionally a Main switch can be used to isolate the positive busbar from the battery.
The SmartShunt connects via Bluetooth to the VictronConnect app on a phone or tablet and you can conveniently read out all monitored battery parameters, like state of charge, time to go, historical information and much more.
 |
3.3.2. smallBMS with Cyrix-Li-ct as a battery combiner
The below system example shows a small DC system in a RV or Boat. The main components are:
The Charge disconnect output of the smallBMS controls the BMS charge disconnect input of the Cyrix-Li-ct (pin 85). In the event of low/high temperature or cell overvoltage, the Cyrix-Li-ct will stop charging the lithium battery.
DC loads are controlled via a Smart BatteryProtect. Its remote H input connects to the Load disconnect output of the smallBMS. In the event of a low cell voltage, the Load disconnect output and as a result the remote H input of the Smart BatteryProtect becomes free-floating and disconnects the DC load to prevent further battery discharge.
A remote on/off switch wired between the battery positive busbar and the remote H input of the smallBMS can be used to switch DC loads and chargers off, additionally a Main switch can be used to isolate the positive busbar from the battery.
The SmartShunt connects via Bluetooth to the VictronConnect app on a phone or tablet and you can conveniently read out all monitored battery parameters, like state of charge, time to go, historical information and much more.
 |
3.3.3. smallBMS with Phoenix Inverter
The below system example shows a small DC system. for example, in a Camper. The main components are:
The Charge disconnect output of the smallBMS controls a SmartSolar Charger via a VE.Direct non inverting remote on/off cable (not necessary with larger MPPTs that have a remote on/off port). In the event of low/high temperature or cell overvoltage, the solar charger will stop charging.
A Phoenix Inverter VE.Direct 12/375 allows powering domestic equipment. Its remote H input connects to the Load disconnect output of the smallBMS. In the event of a low cell voltage, the Load disconnect output and as a result the remote H input of the inverter becomes free-floating and disconnects the Phoenix inverter to prevent further battery discharge.
A remote on/off switch wired between the battery positive busbar and the remote H input of the smallBMS can be used to switch DC loads and chargers off, additionally a Main switch can be used to isolate the positive busbar from the battery.
The SmartShunt connects via Bluetooth to the VictronConnect app on a phone or tablet and you can conveniently read out all monitored battery parameters, like state of charge, time to go, historical information and much more.
 |
3.4. Installation
Before installation, make proper system design considerations to avoid unnecessary connections and to keep cable lengths as short as possible. See also the System Examples chapter.
Preferably mount the smallBMS on a flat surface.
Pull off the wire loop of the remote on/off terminal to prevent unwanted switching of the smallBMS.
Install and connect appropriate fuses and all electrical wiring, leaving the negative pole of the lithium battery disconnected from the system.
Daisy chain the battery control cables between the lithium batteries and connect the ends to the BMS port. To extend the communication cables between a Lithium Battery Smart and the BMS, use the M8 circular connector Male/Female 3 pole cable extensions.
Reinsert the wire loop to the remote on/off terminal of the smallBMS. Alternatively install either an on/off switch between Remote L and Remote H or switch Remote H to battery plus, or Remote L to battery minus.
Connect the negative pole of the lithium battery to the system.
The smallBMS is now ready for use.