Build a 5-Point Temperature Monitor for a Victron Home Battery Setup

Steps

1. 1

   Step 1: Installing temperature controllers in the front panel

   I start by placing the temperature controllers into the tight holes of the front panel. The display modules do not need to be screwed down because they feature clips on the bottom that snap into place when pushed through the front. I repeat this mounting process for all five temperature sensors.

   While working, I notice the small display boards can fall out easily if the back covers are removed, so I put the displays and back panels right back in place.

   What I used

   Item	Amount	Notes
   W3230 DC 12V temperature controller	5	Temperature control range from -55 to 120 degrees Celsius

2. 2

   Step 2: Gluing the controller label plate

   To give the unit a finished look and make its function clear, I glue a separate label plate right underneath the temperature controllers. This makes the layout of the panel visible and complete.

   What I used

   Item	Amount	Notes
   3D printed housing and label plate	1	Printed using free 3D models

3. 3

   Step 3: Preparing the buck converter

   My Victron setup uses a 48 volt system, but the temperature controllers work on 12 volts. To bridge this gap, I use a buck converter that can take up to 90 volts on the input and step it down to a steady 12 volts. Since the buck converter online pictures did not show any mounting screw holes, I glue the converter directly into the deksel, which is the lid of the housing.

   Next, I solder input and output wires to the converter, including an inline fuse on the input for safety.

   What I used

   Item	Amount	Notes
   Buck converter	1	12V output, 16V to 90V input range
   Fuse	1	Placed on the input for safety

4. 4

   Step 4: Wiring the thermometers to the buck converter

   I examine the back of the five controllers, which have positive, negative, and switched contact connections. I cut short wires and solder the positive output of the buck converter to the VCC inputs of all the thermometers. Then I do the same for the negative wires, connecting the negative output of the buck converter to the ground connection of every single controller.

   Now all five temperature sensors are wired to power.

   What I used

   Item	Amount	Notes
   Wire	several	Used for power connections between the buck converter and controllers

5. 5

   Step 5: Closing and testing the housing

   I solder a black negative wire and a red positive wire to the input of the buck converter with a fuse attached. I pull the cables through the housing hole and close the unit using small screws to keep the wires secure. Finally, I connect the negative cable and then the positive cable to the busbar.

   All five thermometers light up and display the current temperatures.

   What I used

   Item	Amount	Notes
   Small screws	several	Used to close the housing
   Busbar	1	Power distribution connection point

6. 6

   Step 6: Setting up temperature thresholds and relays

   The controllers come with default settings, including a default switching temperature of 28 degrees Celsius. To change this, for example to cool the MultiPlus when it reaches 35 degrees, I press the set button once. The bottom text blinks, and I use the plus and minus buttons to adjust the target temperature.

   There is a small tolerance difference of 2 degrees so the relay does not constantly cycle on and off.

   What I used

   Item	Amount	Notes
   W3230 temperature controller	1	Configured via the set button and arrows

7. 7

   Step 7: Wiring external devices like fans, alarms, and lamps

   The internal relay is normally open and closes when the target temperature is reached. For a 12V cooling fan, I tap into the 12V VCC supply, connect it to the first relay input, run the relay output to the fan positive wire, and connect the fan negative to the ground. You can use the exact same setup to connect a loud 12V alarm if the battery set gets overheated past 50 or 55 degrees.

   Because the relay is isolated, you can also run mains voltage through it to switch a lamp on and off based on temperature.

   • Cooling fan to prevent overheating

   • Acoustic alarm for high temperature warnings

   • Mains powered lamp switched via the relay

   What I used

   Item	Amount	Notes
   12V cooling fan	1	Example device for cooling
   12V alarm	1	Optional over-temperature warning device
   Lamp and power plug	1	Example for switching mains voltage

8. 8

   Step 8: Teasing the next video and call to action

   In the upcoming video, I will show you how to add two extra fans inside the Multiplus for quieter cooling. I set these fans to kick in five degrees below the standard Victron temperature so they handle the cooling first and reduce annoying fan noise. If you have any questions, comments, or want to know if something else is possible, please drop them in the comments below.

   If you like the video, give it a thumbs up because that helps me a lot, and remember that you can find all the 3D model links for this project in the description.

9. 9

   Step 9: Takeaways

   • Always check that you order the 12V version of the W3230 temperature controller.

   • A buck converter safely steps down the 48V system voltage to power the 12V controllers.

   • Always place a fuse on the input side of the buck converter for safety.

   • The controllers feature an adjustable hysteresis difference to prevent rapid on-and-off switching.

   • The internal relay can switch 12V fans, alarms, or even mains voltage depending on your setup needs.