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3. Installation and configuration
3.1. Important 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 that are not connected to the System+ port 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 Smart BMS 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
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
Note: please check the residual current of the load when in off state.
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 Smart BMS can be used to control the remote on/off terminal of a BatteryProtect.
Page 4
Smart BMS 12-200
Inverting remote on-off cable
Appendix A [11]
can be used. See
Appendix A
[11].
Installation and configuration
for a
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