Frequently Asked Questions - Victron energy VE.Bus BMS Manual

7. Frequently asked questions

Q1: I have disconnected the VE.Bus BMS, and now my Multi or Quattro will not switch on, why?
A Multi or Quattro programmed with the VE.Bus BMS assistant, and unable to find a VE.Bus BMS on the bus, will go into an
emergency mode. In this mode it will charge the batteries with 5 Ampère max, up to 12V, 24V or 48V, depending on system
voltage. Note that in this mode, the only LED which is on is the Mains On LED. If you disconnect the AC input from the
Multi/Quattro, it will switch off. It will not start to invert since it cannot get verification on the battery health from the VE.Bus BMS.
Note that, when the batteries are depleted or disconnected, Quattros need to be powered from AC input 1. Supplying power to
AC Input 2 will not make a Quattro switch on and start charging.
Q2: The batteries are empty and the Multi/Quattro will not start to charge, how to get the system up and running again.
When lithium batteries are depleted (the voltage is around 9V or even lower) the battery voltage might be below the operating
window of the VE.Bus BMS. In that case the VE.Bus BMS will not be able to start the Multi/Quattro, even if an AC Detector is
installed. To start the system again, disconnect the VE.Bus BMS from the Multi, and refer to Q1. Note that it might be necessary
to disconnect any Blue Power Panels, NMEA2000 interfaces or other similar smart products. As long as they are not switched
on themselves, they can prevent the Multi/Quattro from starting up.
A simpler option to revive a depleted system might be to connect a small battery charger, for example 5 Ampère, and wait for
the battery voltage to get back up to 12 Volt.
Q3: What happens with the Multi/Quattro when the BMS gives a low cell voltage signal?
The Multi/Quattro will be in charger only mode: when AC input is present, it will charge the batteries. And when the AC input is
not present, it will switch off.
Q4: What happens with the Multi/Quattro when the BMS gives a high cell voltage signal?
The high cell voltage signal will only be given when there are unbalanced cells. The Multi/Quattro will switch to bulk, and starts
charging with a reduced charge current. This allows the balancing system to rebalance the cells.
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