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BMV-702 temperature sensor type

Is it a thermocouple, resistance (PT-100, PT-1000, other) or some other kind of sensor?

BMV Battery MonitorTemperature Sensor
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I can confirm that it is not an LM335Z, and I'm pretty sure it is not a PT100 or PT1000, as those are RTDs (Resistance Temperature Detectors). I am fairly certain that it is a NTC Bead Thermistor (we had a damaged one that we opened up to look at). My calculations indicate a 150kΩ (@25°C) with a B parameter of approximately 4021K. The only issue is that I can't seem to find one from suppliers like Mouser or Digikey.

It is definitely an NTC Bead Thermistor. We found one that is close. Vishay PN NTCLE100E3154GB0. B-parameter of 4370K. It is remarkably close to the Victron original.

@dtaschler, what makes you say it's an NTC thermistor? I recently bought a BMV-712/BMV-702 sensor (ASS000100000), and attempted to measure its open-circuit parameters: it has > 10MOhm resistance, and is also open in both directions when tested as a diode (to 17V).

I'm guessing it's a LM35 or similar IC configured in a two-wire circuit (e.g. figs 17, 19 of the LM35 datasheet).

2 Answers
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wkirby answered ·

It's a bit of a mystery at the moment.

I'm pretty sure it's not a thermocouple.
I'm pretty sure it's not a data type one like DS18B20

I think it's most likely a zener based one like LM335Z (but it is not LM335Z).
Resistive is quite possible too.

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aare answered ·

So if we share one temperature sensor output between two BMV-702, shall additional error be small, like less than 1 deg C?

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Hi Aare; you’ll have to test that to find out. I’m sorry but its not a use case common enough thath I want one of our r&d engineers to spend time on making an answer.

Being that the temp sensor uses resistance, it is possible that there will be significant error when two BMV devices are in parallel.. As stated earlier, test to confirm.