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Schnitzel avatar image

MultiPlus: Disable Charger based on battery temperature

I'm currently building an RV off-grid system based around a Lithium Tesla Battery and MultiPlus. In the system is also a BMV 702, BatteryProtect 220 and Color Control.


As the Lithium Battery really doesn't like to be charged below freezing temperature I'm planning to have an automated heating pad that keeps the battery warm, but I would like to have a fail safe which disables the MultiPlus Charger whenever the temperature of the Battery reaches 5°C

My current setup is to connect the BMV-702 Temperature Control Sensor to the Battery and then connected the BMV-702 Relay to the MultiPlus AUX1 which controls the Charger via the Charge Assistant. This works nicely, but I was wondering:

1. The MultiPlus already has a Temperature Sense Connector plus the Temperature Sensor shipped, when I measure the voltage of the Temperature sensor I get a reading of 2.6V at 25°C. Is there any datasheet of the Temperature Sensor that I could use to configure the MultiPlus Assistant for temperature? I would really like to not depend on the BMV for the temperature measuring and best have the MultiPlus measure the temperature directly.

2. I found the new Shared Temperature Sense feature of the Venus/ColorControl: https://www.victronenergy.com/blog/2018/10/17/venus-os-v2-20-scheduled-charging-equalize-and-more/ which mentions:

the Venus-device will send the battery temperature to the connected Solar Chargers and Inverter/chargers.

But I don't see anything in the MultiPlus Configuration Screen to do anything with that Temperature or any other way that it actually receives the temperature form the Venus/ColorControl.

Plus just two other small questions:

1. Is there any way to see the current voltage reading on the MultiPlus AUX inputs? I'm having a bit a hard time to find the correct voltages to use in the Assistant

2. When I disable the Charger in the VEConfig all together, but then enable the Charger again via the Assistant based on the AUX1. The charger is actually running! That's a bit scary ;) Also which charge settings are used? I assume just the last settings of the charger before it was disabled all together?

Multiplus-IITemperature Sensortemperature
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2 Answers
johannes.hovda avatar image

I would like to do a similar variation of this, to restrict max charge current to 10% of the battery capacity if the temperature is at or below freezing.

Can I achieve that on the Multiplus using the Multiplus Temperature Sensor (for ambient temperature sensing) and an assistant? In other words, not an on-off relay function, but rather a dynamic config change?




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mvader (Victron Energy) avatar image

Hi Schnitzel, welcome to the community; and sorry that this answer took a while.

1. Datasheet for the temp sensor: no we don’t have one available; sorry. Putting it in the freezer would perhaps be the most practical solution :-).

At some point we’ll add a feature in the inverter/charger itself so that you can configure it to stop charging at a certain temperature; just like our solar chargers already have.


For any other readers thinking about their lithiums:

- Victron VE.Bus BMS connected-, or BMS 12/200 connected-, Smart lithium batteries will stop charging; there the logic and temperature measurement is in the battery; and controls the connected equipment like the Multi. See recent Smart Lithium firmware update for details.

- same thing for CanbusBMS connected batteries like BYD or Freedomwon: the battery itself measures temperature and decides what to do by logic implemented by the battery manufacturer.


2. What does the Multi do with the temperature: it uses it to compensate the charge voltage. Only for lead batteries: lithium doesn’t need charge voltage compensation.


1-small: voltage reading on aux inputs: no; not available. Nice advanced feature though!


2-small: indeed. Last settings. Yes; its the issue with the Assistants:: gives you lots of power! :-)

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