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saskak avatar image
saskak asked

Second smart shunt for temperature sensor wiring to mppts

I have a very simple system with a victron smart shunt 500A, 2x victron smartsolar mppt 100/30, 24V battery bank (2x FLA C20 100Ah), Victron Energy Phoneix 24V 1200VA inverter and 2x 340W panels on one array and 410W on another (2nd mppt), but will eventually add another 410W to that. All connected via victron VE direct cables to a PI3 (VE.direct to USB). DVCC on with voltage/current/temperature shared across.

The smart shunt is wired to measure mid-point and I also have a battery balancer hooked up. I am currenlty using the internal temperature sensors of the mppts for temperature correction, but would like to use the proper battery sensor. I do have the correct sensor and tested removing the mid-point. I am in the process of buying a second smart shunt to accomodate the temperature sensor.

My question is do I set this second smart shunt as a DC load or generic shunt?

Can the temperature sensor be put on that DC load smart shunt and will it be seen across the system?

Can the MPPTs be on the second shunt or they must be on the primary smart shunt?

I suspect that they can be hooked up on the DC load smart shunt. Of course the main negative from the battery will come to the primary smart shunt and nowhere else. The inverter will be on the primary shunt. Does it actually matter as both shunts will report all the voltages/current to the pi3.

Many thanks indeed for any help, much appreciated.

SmartShuntTemperature Sensor
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saskak avatar image
saskak answered ·

OK, after some testing it is working as intended.

One can get a battery sense temperature sensor and hook this up in a ve network. The smart shunt (via ve.direct) works as a mid-point. Problem with that is that there might be clashes between the ve network (temp sensor and the two MPPTs also connected via ve.direct) as both MPPTs are synchronised and I am not too sure what the consequences are with the DVCC on. I want the DVCC to limit the current to the batteries.

How I set it up and I am happy with that is a second smart shunt with a wired temperature sensor. A bit expensive for just the addition of a temperature sensor, I know. The first smart shunt is the primary smart shunt and measures all the voltages/current and the mid-point, the remote VRM console confirms that this is the primary battery measurement shunt. The second smart shunt is just a shunt and shares the measured AUX temperature via the DVCC. DVCC picks it up without a problem and shares it with the two MPPTs. All works great, no problems whatsoever. The second shunt has to be as a Smart shunt and not just DC load. As a DC load shunt, the DVCC does not pick up the temperature values.

If anyone wants both mid-point and a temperature sensor with the PI3, then it is a second shunt unfortunately. Hope someone finds that useful.

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kai-fuchs answered ·

Why don't you buy instead the Bluetooth temperature and voltage sensor for the MPPT?


https://www.victronenergy.com/accessories/smart-battery-sense

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saskak avatar image saskak commented ·
Apparently it is not good to mix ve.direct to usb and the smart ve.network as the Bluetooth tem sensor has to be via smart ve.network. Unintended consequences and they do not mix very well. That is as far as I understood, maybe I am wrong.
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kai-fuchs avatar image kai-fuchs saskak commented ·

I don't understand, the sensor is especially intended to supply one or more mppts with the actual battery voltage and temperature.

It's not recommended to use the Bluetooth sensor and the sensor of the shunt at the Same time. But I'm not sure whats the difference, if the smart battery sensor is sharing Temperature via Ve-direct network or the shunt is sharing temperature via Ve-direct network with the MPPT.

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saskak avatar image saskak kai-fuchs commented ·

The smart sensor will be sharing battery temperature via smart network, where the shunt and the mppts will be in ve.direct. The smart sensor is giving the temp via bluetooth, so a smart network. If I have a cabled temp sensor then I cannot have the mid-point as well, which is important to me.

In the smart battery sense manual: "Smart Battery Sense is not needed, or allowed, in systems which are already controlled by a Color Control GX or Venus GX". I already have a Venus OS from the pi3, so not quite possible that way.

To be honest I am also puzzled why it cannot be done, it should be possible.

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kai-fuchs avatar image kai-fuchs saskak commented ·

The FAq said the following.

Q5: Can I use Smart Battery Sense in systems already controlled by a GX device (eg CCGX/VenusGX)?

Yes, but keep in mind that if, voltage or temperature information is also present on the GX Device, the charger will use that information in favor of the information coming from the Smart Battery Sense. The GX device already has, in most cases, voltage sensing (soon they will have temperature sensing too), so adding a Smart Battery Sense to the installation is not necessary. For further information please see: CCGX/Distributed Voltage and Current Control.



In my mind this means, it's not necessary to use a Bluetooth sensor, if you have a T-Sensor connected to the gx device that's already measuring batt temperature. This should not apply to your use case.

In my system I have both the Bluetooth and the sensor at the shunt shared through Ve.Direct. But the system is only using what's coming from the shunt. The smart sensor was there before shunt and it's kinda sticking permanently to the battery that's why it's still there.

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Kevin Windrem answered ·

I do not think you can only select one battery monitor for all measurements. That is, temperature can't come from one shunt while voltage, etc comes from another.

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saskak avatar image saskak commented ·
Hmm, does that mean that one cannot have both temperature sensor and mid-point with ve.direct cables?
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saskak avatar image saskak commented ·

I did some testing and it can. You can select one smart shunt as the primary battery measurement shunt and the other shunt gives the temperature. The first one also has a mid-point measurements. So, temperature can come from one and mid-point from another. See my accepted answer below.

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jetlag answered ·

I have also the Smart Battery Sense in parallel running to another temp sensor from the BMS.

There is no conflict, but what I don't understand and don't like is, that the Smart Battery Sensor's temperature is not displayed in the GX Device (neither in the device list, nor in VRM,...)

It is taken by the MPPT, but that is all. That's why I also connected the anyway existing temperature sensor of the BMS do have the temperature also in VRM and to see it from everywhere, not only via bluetooth beeing at the battery location.

And although the GX Device has bluetooth, the Smart Battery Sense is not working with the same protocoll. Instead some third party sensors like ruuvi are supported.

Maybe this could be a possibility for you as well, - take a ruuvi sensor (via bluetooth) as temp sensor and let the shunt measure the middle point of your batteries.

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saskak avatar image saskak commented ·
Yes, many thanks for that. I will get a smart battery sense and connect that for the mppt temp correction and the mid point from the shunt. I will post back if it all works, but by the looks of it should be working.

I'm not too bothered by not being able to see the temp, as the batteries are in my garage. I do from time to time check up on them, although it would have been better to see if they are boiling over for some reason.


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