OpenEnergyMonitor Community

External 47K NTC thermistor

hi, is it possible to use that kind of thermister with legs changing the code on the v4 board to get the correct temperature value?

Anythings possible - but why? SMD 10K thermistors are readily available - check Mouser, Digikey etc.

i feel that welding wires on a smd resistor is not good practice and i say that but know that i can do it with my eyes closed, but i always want the best that can be done.

Ah, you didn’t mention these were for external temperature monitoring. If they are for the v4 or v4.21 boards, they need 47K NTC thermistors

sorry yes external, the original B parameter is 4050K but there is no through hole with that value.
I want to use something like this or make one for my leaf battery:

but can the b value be changed in software?

[Jon_Coop] uses the 10k so that is why his readings are off.
but it would be more important to have a accurate reading on the cell,
a few degrees off on the board should be ok when balancing.

Stick to 47k - those parts from LCSC look good - the B value is configurable in the software, but you may have to create a custom firmware/compilation.

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Got these murata thermistors: NXFT15WB473FA2B150 47k 4050K
Very tiny and the same spec as the smd one on the v4.0 board but they have all the values you need.
Will use thermal epoxy to stick it to the ring terminal.

r44e-3685.pdf (861.0 KB)

after some thermal epoxy.
on the leaf cells the sensors are located on the middle terminal in 3 locations.

Nice work

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a bit of advice, after looking at a temperature difference of 4ºc (17 to 21 at 21º ambient temp) i recomend testing all modules and all temperature sensors at once and discard the ones that are out of spec.

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Which retailer did you buy the thermistors from?

mouser and they are 1%, but the smd ones are the board are 3% and much more consistent.

Did you solder them? They are sensitive to heat, and over temperature can damage them.

oh i have heat shrink on the tip not to damage the wires when i crimp, that could be it.
the wire is 100mm long so no problem soldering.