question

somewhereinusa avatar image

prevent charging below 34 deg F

Is it possible to prevent charging of a lithium battery bank on a multiplus using some sort of temp sensing device?

Lithium Battery
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Justin Cook - Bay Marine Supply USA avatar image

@somewhereinusa, if you have your Multi set to "lithium" mode, this disables its internal temperature compensation because the Multi is assuming your BMS will handle that by itself. Since you don't technically have a BMS (the Valence cells referenced are not drop-ins, though they can technically and very marginally be used without one) and you want temperature compensation, you'll need to switch the Multi out of lithium mode, which will then permit that "low temperature" switch to remain on.

Then, you'll just need to go through and make absolutely certain that all your charge voltages, rates, and current are set appropriately, since you can't use the proper lithium setting.

This is part of why Valence cells and other cobbled-together LiFePO4 battery banks are expressly not supported by Victron, because they don't have the necessary built-in safeguards that protect not only the battery bank itself, but also all the components connected to it and, for that matter, the end user.

No judgment, just... there's a very good reason for why a Valence battery is half the price of any comparable LiFePO4 drop-in, and that's because it doesn't have the necessary BMS to ensure safe and proper functionality.


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Justin,

Your attachment is confusing. Lead temperature compensation is to charge lead Batteries at a higher voltage during lower temps since Lead resistance goes up during lower temps. Li ion does not need this voltage increase because Li Ion does not have the increased resistance.

What this user is needing is to stop all charging from the Multiplus to his Li Ion once the temp of the battery goes below a set temp like 45 deg F.

This can be done with a BMS alarm signal wire connected to the Temp sensor on the Multiplus and the use of an assistant. Since he does not have a BMS he can do it with a simple thermostat you can get off Amazon for $7 that will send a power signal to temp sensor on the Multiplus and an assistant. No need to purchase a BVM712 for $250 and a CCGX for $500 to get this function. My $150 Electrodacus SBMS0 will also work to send the alarm under temp signal to the Multiplus to shut off charging.

@Tom, I feel confident that if you read the thread, you will see why I posted what I did. The OP was wondering why the switch that doesn't allow charging below 5C wouldn't stay "on" in VictronConnect, and it's because the OP has the MultiPlus in lithium mode.

Victron does not support the usage of aftermarket 3rd-party $7 Amazon thermostats hooked to their components, so for anyone else reading this, I strongly discourage that approach.

There is NO replacement for a BMS.

Also, no one suggested any purchases of a BMV or a CCGX, so I'm not sure what you're responding to there.

somewhereinusa avatar image

That doesn't exactly answer the question. The VictronConnect software has a switch that, according to the explanation, will not allow charging below 5°C. The Multiplus has a temperature sensor attached to the battery. The switch will not stay switched to "on". Shouldn't need an external BMS. I have the problem handled another way but, I shouldn't have to. How hard would it be to simply not charge below a certain temperature, no matter what other settings are? The software seems to support it, but it doesn't work.

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I will be honest, the instruction manual for the Multiplus does not talk much or at all about this subject or using assistants. I have the temp sensor connected to my battery and the Multiplus, but have no idea what it does. My thought was this option was to adjust the current charge on a cold lead Acid battery. I have this function shut off since I use Li Ion.

Please let us all know if you get it figured out using Multiplus assistants.

blond2silver avatar image

Hello, I have configured temperature to cutoff MPPT charging, but the system I've implemented has a BMV-712, and a CCGX (colorcontrolGX) gateway. I have enable DVCC within the CCGX parameters as well as enable STS (shared temperature sense). The BMV-712 is enabled as the overall battery monitor as primary source. Within the MPPT, I've configured the low temperature cutoff for 0degrees Celsius (32 degrees Fahrenheit). I haven't had a chance to really test this yet; testing would be by raising the MPPT low temperature cutoff to 50 degrees Fahrenheit, which is the max setting, because it hasn't been cold enough yet. I should also mention that the system I have implemented battery bank is Battleborn based which has integral low temp cutoff within each battery's BMV. So in essense, the use of DVCC and "STS" should be redundant.

My quesition is does your system have a CCGX or Venus gateway, and a BMV-712 battery monitor, and if so perhaps this might be a good method as described above without all the additional electromechanical relays etc?

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I'm using Valence U27-12XP (12V drop in modules bought used). They have internal BMS but, Valence does not support or, apparently, even want us small fry to even have them. Information is sketchy. They do however work well.

I'm monitoring with a BMV 700 (doesn't have temperature), charging with a Multiplus controlled by Digital Multi Control 200/200A GX . Solar isn't installed yet so. Solar isn't installed yet so no MPPT.

Tom avatar image

Yes. The temp sense on the Multiplus can stop charging is you have an external BMS that will send the alert signal. My BMS is set up this way as it has a thermistor attached to the battery.

Update 1 /30/2020 i need to add you need to install the two signal bms support assistant for this function. So yes Victron supports this.

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somewhereinusa avatar image

OK, I feel dumb, if the contactor is open the batteries are unhooked preventing charging, regardless of whether there is voltage on the other side of the contactor.

I'd still like to know about the lithium battery setting in VE connect.

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somewhereinusa avatar image

Still trying to get this sorted out. I have a contactor that will unhook the batteries from everything when temperature reaches a certain point. The problem is if the relay trips and there is still mains power coming in there is still 12Vdc coming out of the DC side, I assume because AC pass through is still working. If I turn off mains then everything is shut down.

I have tried telling the MultiPlus , through VE connect, that I have lithium batteries, which is supposed to disable charging at about 5° C. That switch will not stay ON.

Seems like this should be a simple thing since, from my understanding, no lithiums should be charged below freezing and there is a switch for this. I just won't work.

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Tom avatar image

If you are using Li Ion Batteries without a BMS thermo control, yes you can build a circuit with a simple temp control unit that will turn on and send a signal to a simple relay to not allow your charge source to turn on of below a specified temp.

If you use the Multiplus as your charger, there are built in Temp sense your relay can be connected to to shut off the charging function.

Like the other post many batteries have a built in BMS to not allow charging at low temp like Battle Born and Victron with the external BMS system.

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Kevin Windrem avatar image

If you have a battery with built in management, it may do this for you. Check your battery specs. Not all do.

Like most drop-ins, my BattleBorn LFPs protect the battery against low temp charging, high temperature current draw, excessive current draw, high and low voltages, and depleted state of charge. They also use the "absorption" charge cycle for cell balancing.


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