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treejohnny avatar image
treejohnny asked

Multiplus assistant to turn charger off with low temp for Lithium battery bank.

I have Multiplus 3000, Venus GX, BMV712 and Lithium Battery Bank. Is it possible to use temp from BMV712 to turn off charger with low temp to help protect Lithium battery?

MultiPlus Quattro Inverter ChargerBMV Battery MonitorVenus GX - VGXAssistants
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4 Answers
wkirby avatar image
wkirby answered ·

This is not the correct way to do this and that is why there is no assistant for what you propose.

You should be using a BMS which will monitor the temperature (and Voltage) of each cell. If you are using a third party BMS then you can use the "Two Signal BMS Assistant" to send "enable charge" and "enable discharge" signals to the MultiPlus.

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I am looking for 'redundancy' to protect my Lithium battery. There is no wrong way to do this.

Drop in Lithium does not let you into the BMS.

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klim8skeptic avatar image
klim8skeptic answered ·

Hi Johnny,

You don't say what Li batteries you have, or if you are using some sort of BMS.


For my system,

Winston 300ah cells

Basic cell voltage monitoring/balancing BMS

2 x Victron mppt

BMV 700

Multiplus

Venus gx.


I have used my Venus with a Multiplus temp sensor, enabled DVCC, STS, SVS, SCS. (You could use the bmv712 as the temp sensor)

That seems to work fine at disabling the mppt charge (once you choose the right temp sensor, there is 2 to choose from), once the temp sensor goes below 5c. The mppt seem to respond to the STS delivered via the Venus.

I don't know if my Multiplus will react the same way when tested (it no longer has a temp sensor), and I have never had the need to charge the Li batts from it.

Pretty sure that a std Multiplus with temp sensor, and set to Li batteries will disable charging below 5c.

Read the manual, CCG, and Venus.

Edit, Venus os v2.41, Mppt firmware v1.47.

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I do have the Multi set to Lithium battery but it does not have a dedicated temp sensor. The 712 has the temp sensor, I was hoping the 712 would share with connected devices. Maybe because I disconnect the Venus to program the Multi, the low temp doesn't show while programming? Will the same temp sensor work on multi and 712?

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" I don't know if my Multiplus will react the same way when tested (it no longer has a temp sensor), and I have never had the need to charge the Li batts from it."

I have now tested whether the Multi will stop charging Li batts on my system, below 5c.

Under Venus control (STS), once my temp sensor got below 5c, the mppt's cut charging, but the Multiplus continued to charge. As expected.

Tomorrow, time and sun permitting, I will move the temp sensor back to the multi, and test.

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Tom avatar image
Tom answered ·

There is an assistant for the multiplus to do this. It is call 2 signal bms support that controls the temp sense and aux IO ports as a NC or NO circuit. Pretty easy to set up to stop charging.

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tom-roger avatar image
tom-roger answered ·

I also have the same challenge. I have 4x Toband LiFePO4 24V/50ah cells connected to a MultiPlus 24/3000/70-16. These are drop-in cells with internal BMS (no low temperature charge protection). These are not capable of communicating in any way. There's no temperature sensor connected my MultiPlus charger, and I am wondering if I should by one? I also have BMV-712 Smart monitoring the SoC of the batteries. I am planning to use the 2nd input on the shunt for monitoring the voltage of the starter batteries. That's why I would like to use the internal temperatur input to monitor the temperature of the batteries.

Is this possible now? I have read that Victron is planning to add an assistant or feature to do this? Any other way to protect the batteries from being charged below zero?

I also have a Color Control CX. This panel has a potential free contact. Could this be programmed to close when the temperature is below 5? Could this be connected to the Aux input on the charger? Any feature for shutting of the charging?

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Tom-Roger - My understanding is that we have to use the 2 wire assistant in the Multiplus via the MK3. The temp input will have to be either a BMS or BMV712. If I am right you will have to something creative to monitor starter battery voltage.


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