featherlite
Solar Enthusiast
I have two Victron Smart Battery Sense units. The reported temperatures differ by about 4 degrees F at 70 degrees F. I have searched but find no way to calibrate these units. Does anybody have any advice?
Can a Victron Smart Battery Sense be calibrated? Mine do not accurately report temperatures.
- Thread starter featherlite
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sunshine_eggo
Happy Breffast!
Are these attached to batteries or simply sitting adjacent each other in ambient air?
I ask because I have noteworthy temperature differences across my battery based on location. I have BMV-702, 3X Batrium temp sensors, two Quattro sensors and a SBS.
4°C difference. THis correlates relatively well to the trend reported by an IR thermometer.
Placement of sensors on a battery bank may very well see different temps.
I ask because I have noteworthy temperature differences across my battery based on location. I have BMV-702, 3X Batrium temp sensors, two Quattro sensors and a SBS.
4°C difference. THis correlates relatively well to the trend reported by an IR thermometer.
Placement of sensors on a battery bank may very well see different temps.
Brett V
Mad Scientist
4 degrees at 70F is less than 5%... probably within the margin of error.
sunshine_eggo
Happy Breffast!
Unless they're using absolute temperature.
70°F = 530° Rankine
4° / 530° = 0.8% error
Probably not since it's unlikely to be used at absolute 0, but it's probably a % accuracy over a much larger range of operation, e.g., -40° to 120°F is a realistic range... 4/160 = 2.5%
Brett V
Mad Scientist
It's a European design, so most likely based on Celsius using an off the shelf thermistor based sensor. Your math skills are way ahead of mine.
sunshine_eggo
Happy Breffast!
featherlite
Solar Enthusiast
Thanks for all the replies.
My understanding is that Victron uses a standard NTC (Negative Temperature Coefficient) thermistor. My research discloses that, typically, in my application's temperature range, these thermistor's have an accuracy to within 1/2 degree F.
I have tested my Victron probes in ambient air and when taped to the side of a cell.
My other non Victron thermistors are more much accurate than the Victron unit.
Disclosure: I have very limited knowledge.
My understanding is that Victron uses a standard NTC (Negative Temperature Coefficient) thermistor. My research discloses that, typically, in my application's temperature range, these thermistor's have an accuracy to within 1/2 degree F.
I have tested my Victron probes in ambient air and when taped to the side of a cell.
My other non Victron thermistors are more much accurate than the Victron unit.
Disclosure: I have very limited knowledge.
sunshine_eggo
Happy Breffast!
featherlite
Solar Enthusiast
The only thing I was concerned about was the temperature set point for the "low temp charging cut off" parameter on my Victron Smart Solar MPPT charger. My Smart Temperature Sense reads about 4F high at 70F. I do not remember how far it was off at 32F .IMHO, 4°F is just not enough to worry about.
On the other hand, it could be my OCD LOL!
sunshine_eggo
Happy Breffast!
IIRC, the default on the MPPT is 5°C.
While I have a SBS and the other temperature sensors, the BMS is running the show. Since it's in communication with the GX, and I have notable temperature uncertainty, I have two set points:
7°C: The BMS instructs the GX to limit charging current to 0A. This allows the MPPT to respond to drops in voltage due to load and supply loads with PV. This isn't perfect, and I might see ±0.3A when loads are steady, I will see big fluctuations when loads turn off, BUT they are very short lived and return to the ±0.3A value very quickly.
Freezing isn't a cliff, i.e., they can be safely charged at rated current above freezing. They can still technically be charged at lower rates at and below freezing. This depends on the cells and without specs from manufacturers, one can't be certain; however, VERY low charge rates like 0.05C at and just below freezing are almost certainly safe. My cells are 450Ah, or 22.5A. This equates to about 1200W. The aforementioned transients are almost always within this, and I'm always above freezing.
At 1°C, the GX cuts off all chargers, i.e., the remote relay on both the MPPT and Quattros are opened to completely disable the Quattro AC chargers and to turn the MPPT off. I'm running purely on battery at this point.
You won't have the luxury of the active feedback loop, but simply settings to something conservative like 5°C should eliminate inaccuracy issues.
featherlite
Solar Enthusiast
sunshine: Thanks for the education. Someday I hope to graduate to the level of installing a GX or equivalent.
sunshine_eggo
Happy Breffast!
sunshine: Thanks for the education. Someday I hope to graduate to the level of installing a GX or equivalent.
I drug my feet on this one... Even though I bought it at the same time, I didn't install it until after the MPPT/Quattros were online for awhile. Once I got it connected, it solved a big issue I had with over-charging the lead-acid batteries at the time, and the remote monitoring/configuration/control options were ORGASMIC.
Our property is 3.5 hours away, and it was so rewarding to be able to see what was going on and make configuration changes as needed.
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