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3.3. Controlling DC loads and chargers
3.3.1. DC load control
DC loads with remote on/off terminals:
DC loads must be switched off or disconnected to prevent cell undervoltage. The Load disconnect output of the BMS can be used
for this purpose. The Load disconnect output is normally high (= battery voltage). It becomes free-floating (= open circuit) in case
of an impending cell undervoltage (no internal pull down to limit residual current consumption in case of low cell voltage).
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 BMS Load disconnect output.
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, can be controlled with the BMS Load disconnect output via an
cable.
Note: please check the residual current of the load when in the off state. After low cell voltage shutdown, a
capacity reserve of approximately 1Ah per 100Ah battery capacity is left in the battery. For example, a residual
current of 10mA can already damage a 200Ah battery if the system is left in a discharged state for more than
eight days.
Disconnecting a DC load via a BatteryProtect:
Use a BatteryProtect for DC loads that do not have a remote on/off terminal or for switching groups of DC loads off.
A BatteryProtect will disconnect the DC load when:
• Its input voltage (= battery voltage) has decreased below a preset value.
• Its remote on/off H terminal becomes free floating (usually high). This signal is provided by the Load disconnect output
(wired to the remote on/off H terminal of the BatteryProtect) of the VE.Bus BMS V2. See the wiring example
BatteryProtect and a solar charger
3.3.2. DC charge control
3.3.3. Controlling inverter/chargers, solar chargers and other battery chargers
In the event of high cell voltage or low temperature, battery charging must be stopped to protect the battery cells. Depending
on the system, chargers are either controlled via DVCC or must be controlled via their remote on/off terminals and the Charge
disconnect output of the VE.Bus BMS V2.
• In systems with a GX device, you must enable DVCC to ensure that the solar chargers and other DVCC-compatible devices
only charge when they should. See
• In systems without a GX device, the BMS Charge disconnect output must control the solar charger and other chargers, either
via remote on/off, a BatteryProtect or a Cyrix-Li-Charge. See
Page 8
VE.Bus BMS V2
[14].
DVCC operation with VE.Bus BMS V2 [9]
Charger control via Charge disconnect [9]
Inverting remote on/off
System with a
for details.
for details.
Installation
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