I recently installed a Lithium house bank system on a boat utilizing all Victron equipment along with a Wakespeed WS500 Pro alternator regulator. The photo below shows how Wakespeed recommends wiring their regulator’s “Allow To Charge” (ATC) wire to the BMS.
My understanding is that in the event of an imminent BMS disconnection the BMS will send a positive voltage to the common pin of its built-in relay, which would be seen by the Wakespeed and disconnect the regulator before the batteries disconnect, thus preventing the alternator from being damaged.
I would like to wire a pre-alarm warning buzzer to the BMS which would alert me to take action before the BMS disconnects the battery bank. Apparently this is achieved by using the BMS’s internal relay as well. BUT the relay is already occupied by the Wakespeed ATC wire so I don’t think I can use it. Is it possible to have BOTH the ATC and Pre Alarm functionality somehow?
Firstly, your understanding of the feature in wire is slightly wrong. With the Lynx BMS the WS500 needs a 12V signal to work. So when the system is healthy, the ATC relay is closed and the programmable relay is powered and closed so the 12V gets to the feature in. If there is a problem then the programmable relay opens so the feature in wire goes to 0V. This is fail safe if a wire comes loose.
On to your second question, if the programmable relay is used as an alarm it alarms on all conditions even if they are nothing to do with the contactor closing or needing to stop charging. If used as the WS500 early shutdown then you only get 2 seconds of prewarning so not enough time to get a warning and do something.
I believe it is possible to wire a buzzer in. On the wiring diagram, make the following changes.
Go from the 0.5A WS500 fuse to the COM terminal on the programmable relay.
Go from the NO terminal on the programmable relay to one of the ATC terminals.
Connect the feature in wire to the other ATC terminal.
Connect a warning light or buzzer to the NC contact of the programmable relay.
The programmable relay always has a 12V supply and it either sends this to the WS500 feature in or to the buzzer.
Do not forget if you add an alarm as I described above to keep the power draw low as the Aux supply is 0.5A and the Cerbo will take most of this 0.5A and the Aux supply shuts down 5 minutes after the contactor opens.
