Does anyone have a chart that would give the resistance of the battery temperature probe for a freedom25 inverter/charger? I would be interested in the resistance at 80 and 90 degrees F. Also is it necessary to connect it to the positive post. Thanks, john
Sorry, can't help for that model, but the one for the Trace SW4024 is just a pad that is placed against the batteries (between two of them). The other end has a phone jack type plug and plugs into the inverter port. Does not connect to anything other than the inverter.
craig
Quote from: junkman42 on April 21, 2009, 04:02:23 PM
Does anyone have a chart that would give the resistance of the battery temperature probe for a freedom25 inverter/charger? I would be interested in the resistance at 80 and 90 degrees F. Also is it necessary to connect it to the positive post. Thanks, john
Could the resistance be measured at the connector on the end of the probe cable that connects to the inverter? It is supposed to be in the mid 80s tomorrow, I might be able to measure the resistance. Jack
I'm guessing that it's not resistance at all but rather a thermocouple which actually produces a very small voltage.
Most likely, there is a thermister in the sensor. The resistance varies due to temperature, and it's not linear. In other words, the math to convert the resistance to temperature is not pretty.
Quote from: junkman42 on April 21, 2009, 04:02:23 PM
Does anyone have a chart that would give the resistance of the battery temperature probe for a freedom25 inverter/charger? I would be interested in the resistance at 80 and 90 degrees F. Also is it necessary to connect it to the positive post. Thanks, john
Out of general curiosity, why are you looking for this? Are you trying to calibrate your existing inverter, or are you attempting to use this sensor without the inverter?
-Tim
Tim, I have just replaced all of My house batterys and the connecting cables and added individual circuit breakers for each battery. I would like to check the temp sensor to see if it is operating properly. I can not find the information in the manual. And jack that would be absolutely great as the temp should be about the same here tommorrow. If you could check the resistance of Your sensor I will post what Mine reads tomorrow. I assume the sensor is a thermistor but I am not certain of that. I do not have any schematic info so I will poke around and if You would like I will post My results as early as possible. Thanks,John
My Guess - they use this very simple stable SOLID STATE temp device ( LM34 ) 10mv per degree F
see--> http://instruct1.cit.cornell.edu/Courses/ee476/labs/s2004/LM34.PDF
"Also is it necessary to connect it to the positive post"
I believe the Battery temperature sensor goes on or close to the Negative post.
Jerry
John, I bought an aftermarket unit that was said to be a 100,000 ohm thermister. I checked it, and got a resistance reading in that neighborhood. I bought it to use with a C40 controller and it has worked fine, AFAIK.
The resistance drops as the temperature rises.
I was furnished a graph that was supposed to be an aproximate of its curve. At 25 degrees celsius, the resistance is given as 100,000. The drawing is not detailed enough to use it the way that you want to. The paperwork says that it is a direct replacement for the Xantrex BTS, used with Xantrex products.
Good luck.
Tom Caffrey
this may help - especially the first one
http://altenergy.blog-city.com/temperature_sensor_for_trace__xantrex_solar_charge_controlle.htm
http://catalog.selcoproducts.com/viewitems/ermistors-surface-mount-chip-thermistors-sm-seri-2/sm-series-surface-mount-chip-thermistors-sm-series
http://www.greystoneenergy.com/English/products/temperature/TT010.pdf
http://www.sensorsci.com/immersion.htm
http://www.eci.siemens.com/marketplaces/servlet/CoeeSiemensCategoryDisplay?sdc_p=c128fi1000000000003lm34o1000000000003ps2uz2&sdc_sid=25415165266&sdc_rh=&categoryList=273083%2C273378%2C273379%2C273426&categoryId=273431&sdc_bcpath=&sdc_m4r=