Using a BMV 712 alarm as a signal to start a generator
The Victron BMV series Amp Hour Meters have a programmable relay output on the back of the meter. You can program it to operate based on voltage, state of charge, temperature, or other parameters. The procedure is detailed in the instruction manual starting at page 23. Additional help is available in the Victron community forum.
This is the back of the meter:
You can see the relay contacts are set up with common, normally open and normally closed. The alarm can be set to go off with all kinds of parameters but for most purposes you will probably choose either state of charge or battery voltage. If you set the alarm to go off when the voltage gets down to a certain level or based on state of charge then you would use the Common and the Normally Open terminals as your relay output.
The NO and COM terminals are acting as an on off switch, ON when the alarm is active and OFF when it isn't They are not set to carry a lot of current, the amount allowed is specified in the specifications attached to the instruction manual. Here is a screenshot:
If you are using a 12 volt supply then you have to protect it with a 1 amp fuse, you can send it to the COM port and then the NO port will be the signal to turn on your generator. If the generator draws more current on its on/off circuit than 1 amp then your fuse will blow, and in that case you need to put an intermediate relay, so the BMV turns on a relay which sends the signal to your generator. You can Google solid state 12 volt DC relay to find something suitable.
What happens after that is up to the generator and how it is set up to be activated by a remote start signal.
Related Articles
Additional BMV troubleshooting and parameters
The article below explains how the warranty procedure works for Victron. It sounds to me like your meter is working but maybe not adjusted correctly. There are all kinds of adjustments you can do to the meter to make sure it is getting a correct ...Troubleshooting your BMV Battery Monitor
There aren't a lot of things to go wrong with the BMV battery monitor. It consists of three parts, lets look at each in turn: 1. The meter itself. This is the least likely item to give trouble, it rarely is the culprit. You can inspect the ...Resetting your BMV battery monitor when you get new batteries
The instructions for the Victron BMV battery monitor are here. The BMV learns the history of your batteries over time. When you replace the batteries you need to erase the history and start again. Here is what it stores: Here is the relevant part ...BMV Temperature Sensor not working
This is one of the products in our catalog that gets the most user errors on installation. People connect it to the battery first, and then they let the leads flop around before they connect them to the shunt until one of them touches something ...Troubleshooting MultiPlus
Here are some generic tips for troubleshooting a MultiPlus 1. To reboot the processor disconnect the AC and DC connections and leave them both off at the same time for at least 30 seconds 2. With AC and DC power disconnected check for loose ...