How do battery temperature sensors work?

Dec 17, 2016
348
236
Malvern
Funster No
46,488
MH
Hymer A class
Exp
2012
I have recently fitted a Votronic B2B which came with a temp sensor to optimise charging of the batteries ( including lithium). I am planning to get the Votronic Duo MPPT 250 which can be fitted with the same sensor but doesn't come with it (so will cost me more(n)). Would it be possible to use the one sensor but split the wires so that they go to both the solar controller and the B2B ( they will be adjacent to each other)? Ie in parallel.
Below is an extract from the Votronic Duo manual which may help someone (but does help me as I don't know much):


The solar controller recognizes automatically a missing sensor, cable break or short-circuit of the sensor lines, as
well as unreasonable measuring values. In that case, it will switch automatically to the usual charging voltage
rates of 20 °C / 25 °C being recommended by the battery manufacturers.


Obviously I don't want to risk anything if I move over to lithium ( my 7 yr old lead acids are working okay but I'm aware they won't last forever.) but it would both save money and save me having to route another cable (the grommet is quite tight as it is)
Thanks
Paddy
 
Apr 27, 2016
2,642
2,528
Manchester
Funster No
42,762
MH
A class Hymer
Exp
Since the 80s
I don't think you can use one sensor for two controllers. There are lots of methods of measuring temperature electronically. The usual one is a resistor whose resistance changes with temperature.

The controller sends out a known current (amps) and measures the resulting voltage. It calculates the resistance value and works out the temperature from stored data. If the resistance is outside a predefined range, it will report an error.

If you connected the same sensor to two controllers, they would both send out the standard current, so the resulting voltage would be too high and an error would result.

I know Victron devices can communicate the temperature via bluetooth or a data wire between devices, but I don't know if Votronic devices can do this.
 
Last edited:
Mar 14, 2019
427
353
Sutton Coldfield but East Yorkshire man at heart
Funster No
59,127
MH
EuraMobil Terrestra
Exp
Since 2018
I don't think you can use one sensor for two controllers. There are lots of methods of measuring temperature electronically. The usual one is a resistor whose resistance changes with temperature.

The controller sends out a known current (amps) and measures the resulting voltage. It calculates the resistance value and works out the temperature from stored data. If the resistance is outside a predefined range, it will report an error.

If you connected the same sensor to two controllers, they would both send out the standard current, so the resulting voltage would be too high and an error would result.

I don't think you can use one sensor for two controllers. There are lots of methods of measuring temperature electronically. The usual one is a resistor whose resistance changes with temperature.

The controller sends out a known current (amps) and measures the resulting voltage. It calculates the resistance value and works out the temperature from stored data. If the resistance is outside a predefined range, it will report an error.

If you connected the same sensor to two controllers, they would both send out the standard current, so the resulting voltage would be too high and an error would result.

I know Victron devices can communicate the temperature via bluetooth or a data wire between devices, but I don't know if Votronic devices can do this.
Most devices are Thermistors these days for measuring temperature

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OP
P
Dec 17, 2016
348
236
Malvern
Funster No
46,488
MH
Hymer A class
Exp
2012
Thanks autorouter , I had a feeling that might be the case. I'll have to splash out the cash if I go to lithium anyway so in the scheme of things it's not a big deal.

I will be using Votronic as I want to use the S+ for the AES fridge.
 
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