Accuracy of BMS temperature cutout

[rusty69]

Just now, TheBiscuits said:

 

That's the trouble with infrequently read thermometers. If it was used more often you'd know where it was.

 

When I was looking for mine, MrsBiscuit thought it was funny to say "You're getting warmer" as I approached the correct locker!

 

 

Dr Bob was the one for infrequent red thermometers 

[TheBiscuits]

Just now, rusty69 said:

Dr Bob was the one for infrequent red thermometers 

 

Maybe he's got yours!

[rusty69]

1 minute ago, TheBiscuits said:

 

Maybe he's got yours!

Maybe. Or maybe they went with the noodles and duck 

[rusty69]

To finish this one off, according to the IR thermometer, the victron product concurs within 0.5 degrees C. The JBD BMS was way out, and has been adjusted inline with the IR thermometer reading. Victron and JBD now read the same. For how long is anyones guess.

The IR thermometer was on the shelf, but the battery was flat.

[IanD]

3 minutes ago, rusty69 said:

To finish this one off, according to the IR thermometer, the victron product concurs within 0.5 degrees C. The JBD BMS was way out, and has been adjusted inline with the IR thermometer reading. Victron and JBD now read the same. For how long is anyones guess.

The IR thermometer was on the shelf, but the battery was flat.

Interesting, the BMS battery temperature sensor on my boat reads several degrees lower than the Victron ones on generator/motor/controller -- I wonder if it's also wrong?

[rusty69]

1 minute ago, IanD said:

Interesting, the BMS battery temperature sensor on my boat reads several degrees lower than the Victron ones on generator/motor/controller -- I wonder if it's also wrong?

No idea, but its certainly worth checking both against a callibrated instrument if at all possible.Particularily if you are reliant on the temperature measurement switching a BMS on/off.

[magnetman]

I did know the battery was flat but thought the unit was in the box under the step. 

 

Did you check the box? There may be a second unit in there. 

 

 

PP3 battery. Always flat. 

[rusty69]

Just now, magnetman said:

I did know the battery was flat but thought the unit was in the box under the step. 

 

Did you check the box? There may be a second unit in there. 

 

 

There was a spare battery with the DVM. It was one of those rectangular 9V jobs.

[IanD]

1 minute ago, rusty69 said:

No idea, but its certainly worth checking both against a callibrated instrument if at all possible.Particularily if you are reliant on the temperature measurement switching a BMS on/off.

I'll check against a laser thermometer next time I'm there. It seems strange that all three of the Victron sensors agree with each other within a degree or so -- including one on the motor controller which is thermally attached to the baseplate -- but the BMS one is consistently 7C colder. So either the BMS one is wrong or all three Victron ones are, and by the same amount. I know which I think is more likely... 😉

[rusty69]

1 minute ago, IanD said:

I'll check against a laser thermometer next time I'm there. It seems strange that all three of the Victron sensors agree with each other within a degree or so -- including one on the motor controller which is thermally attached to the baseplate -- but the BMS one is consistently 7C colder. So either the BMS one is wrong or all three Victron ones are, and by the same amount. I know which I think is more likely... 😉

Be interested to know the result. Probably a good reason to set the BMS cutoff a good few degrees above freezing too. I think mine was set to 2 degrees. 

[magnetman]

7 minutes ago, rusty69 said:

There was a spare battery with the DVM. It was one of those rectangular 9V jobs.

Thats what I said. PP3. 

[rusty69]

You are a modern day genius.

Edited December 5, 2023 by rusty69