Hi,
Is there an internal temperature node in our Multiplus II?
Not that you can access.
Too bad 
Fit an external one at the exhaust outlet, or use a ruuvi etc.
That is easily sent back to VRM as a virtual temp sensor.
Of course, but then what are the fans based on to trigger?
There obviously are temp sensors, you just can’t access them.
Fans also trigger automatically on load.
And we could hope to have access to it one day..
It seems to me that knowing the internal temperature is a fundamental element, right?
I doubt the architecture permits that, might be wrong. Agree It would be great to have that kind of insight.
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If you want to fit external cooling fans (e.g. to blow cool air in to the MP at the bottom and/or extract hot air from the top) you can use a fan assistant (uses the internal cooling fan state) to switch one of the internal relays – I use the K1 relay to control 2 external 24V fans, one blowing cool air from outside into the electrical cabinet and one sucking hot air out, so these come on every time the internal cooling fans do.
When the weather is hot these come on periodically in the daytime, just due to quiescent power consumption heating everything up – see the sawtooth in “electric cabinet” temperature (sensed using a Ruuvi tag, sitting on the bottom of the cabinet next to the MP/Quattro air inlet)
Thanks for this feedback @iand I do indeed have a ruuvi like you to do this job but I wanted to be sure that there was no possibility of having the internal temperature of the Multi, like that my ruuvi could have been used for something else 
Either way, I’m not sure there’s any point doing anything other than triggering external fans when the MP internal ones come on.
If the internal ones don’t come on the MP thinks it’s cool enough, there’s little point turning the external ones on since there won’t be much cooling air flow over the internal hot bits. If the internal ones do come on, you definitely want the external ones on too to stop the air around the MP heating up.
Exactly what temperature this happens at doesn’t really matter – if the MP decides it doesn’t need extra cooling then it doesn’t need external fans running, if it does need extra cooling then they should be running.
These fans should also have enough airflow to keep the temperature down – I use 2000rpm 140mm 24V fans from Noctua (Quattro 48/10000, one cold air inlet at the bottom of the cabinet, one hot air exhaust at the top next to the Quattro).
I don’t want to add a fan
So why do you want to know what the internal temperature of the Multiplus is, unless you want to take action to lower it if it’s hot?
I find that it is first -rate information that makes it possible to make other developments well beyond a simple addition of a fan
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The multi output power shows a strong degradation by temperature. Some users connect the sensor included with Multiplus for battery sense to the internal torroid transformer. Anyhow, there is already a internal sensor as there is a temperature alarm why I would appreciate to change the boolean format to any numbers by next firmware update. (This is a feature request).
temperatures.pdf (153.5 KB)
I could not have said better 
As has been stated: yes there’s an internal temp sensor but no, it’s not user accessible and it probably never will be.
The reason is in the hardware design of the Multiplus so very unlikely to change.
There’s more info in this thread.
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There are numerous threads about impossible temperature readings. The series circuit of sensor design is to save hardware recources. Obviously, there is only one constant currenct source and one analog input shared for all sensors. Correct circuit would require additional analog multiplexer like the CD 4051 or similar what increses the HW cost.
The result is any average value what is good enough to controll the PWM for fan speed but not for a thermometer functionality with degree celcius calibration. If Victron would publish this value as temperature, the support would be faced with many complaints about unlikely correct values and its accuracy. Therefore they probably decided to shrink the information to a boolean value only.
To communicate this predicament situation with customers after that many requests, is another thing. Maybe our friend @JohannesBoonstra is the candidate to shed some light on this topic at anything like a YT tech talk what we can link if questions appear again and again.
The question is also: how many users actually care to know the internal temperature of their Multis?
I’m guessing most of them just care that they work and to get an alert when things are (almost) running too hot.
The latter part works perfectly with the current hardware design.
Operations-wise it gives no real benefit to know the exact internal temp, except for Geek factor perhaps 
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Yes indeed some are more sensitive to techno than others, moreover they are normally with them with which we exchange on this forum