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battery temperature sensor
Thread Starter
Junior Member
Joined: Mar 2011
Posts: 33
Likes: 0
From: philadelphia
Year: 1997
Model: Cherokee
Engine: 4.0
battery temperature sensor
Just discovered this, and found a rag underneath my battery between the sensor. Sensor doesn't seat too well into the tray hole.
I'm wondering why that rag is there? Maybe
a. the transducer inside is bad sending incorrect resistance to the computer, making it think things are hotter than they really are.
b. someone wanted to keep charging rate unperturbed by batt temp
any thoughts?
thanks
I'm wondering why that rag is there? Maybe
a. the transducer inside is bad sending incorrect resistance to the computer, making it think things are hotter than they really are.
b. someone wanted to keep charging rate unperturbed by batt temp
any thoughts?
thanks
Senior Member
Joined: Dec 2009
Posts: 538
Likes: 3
From: zeeland mi
Year: 1997
Model: Cherokee
Engine: 4.0
yes its for 97 and newer xj's and tj's here is info on what it does.
The battery temperature sensor is actually inside the power module (or SMEC). It measures the air temperature as it flows through the power module, using the temperature to calculate the intake air density and target charging system voltage.
The battery temperature sensor reacts to different temperatures by producing a voltage between .04 volts and 4.96 volts DC, based on an input voltage of 5 volts DC. Because the logic module is so close to the battery, these readings can be used to estimate the temperature of the battery itself. Knowing the temperature of the battery is important because batteries are sensitive to heat, and the logic module will reduce the power sent to the battery by the alternator to prevent “cooking the battery.”
If the logic module detects a voltage outside the normal range (0.04 to 4.96 volts), it triggers a code 44 and the charging rate is set to 14.0 volts as a “safe” option. If the output of the sensor returns to the normal range, the logic module will return to normal operation and it will use the output from the sensor to adjust charging rates.
The battery temperature sensor is actually inside the power module (or SMEC). It measures the air temperature as it flows through the power module, using the temperature to calculate the intake air density and target charging system voltage.
The battery temperature sensor reacts to different temperatures by producing a voltage between .04 volts and 4.96 volts DC, based on an input voltage of 5 volts DC. Because the logic module is so close to the battery, these readings can be used to estimate the temperature of the battery itself. Knowing the temperature of the battery is important because batteries are sensitive to heat, and the logic module will reduce the power sent to the battery by the alternator to prevent “cooking the battery.”
If the logic module detects a voltage outside the normal range (0.04 to 4.96 volts), it triggers a code 44 and the charging rate is set to 14.0 volts as a “safe” option. If the output of the sensor returns to the normal range, the logic module will return to normal operation and it will use the output from the sensor to adjust charging rates.
Thread Starter
Junior Member
Joined: Mar 2011
Posts: 33
Likes: 0
From: philadelphia
Year: 1997
Model: Cherokee
Engine: 4.0
yes its for 97 and newer xj's and tj's here is info on what it does.
The battery temperature sensor is actually inside the power module (or SMEC). It measures the air temperature as it flows through the power module, using the temperature to calculate the intake air density and target charging system voltage.
The battery temperature sensor reacts to different temperatures by producing a voltage between .04 volts and 4.96 volts DC, based on an input voltage of 5 volts DC. Because the logic module is so close to the battery, these readings can be used to estimate the temperature of the battery itself. Knowing the temperature of the battery is important because batteries are sensitive to heat, and the logic module will reduce the power sent to the battery by the alternator to prevent “cooking the battery.”
If the logic module detects a voltage outside the normal range (0.04 to 4.96 volts), it triggers a code 44 and the charging rate is set to 14.0 volts as a “safe” option. If the output of the sensor returns to the normal range, the logic module will return to normal operation and it will use the output from the sensor to adjust charging rates.
The battery temperature sensor is actually inside the power module (or SMEC). It measures the air temperature as it flows through the power module, using the temperature to calculate the intake air density and target charging system voltage.
The battery temperature sensor reacts to different temperatures by producing a voltage between .04 volts and 4.96 volts DC, based on an input voltage of 5 volts DC. Because the logic module is so close to the battery, these readings can be used to estimate the temperature of the battery itself. Knowing the temperature of the battery is important because batteries are sensitive to heat, and the logic module will reduce the power sent to the battery by the alternator to prevent “cooking the battery.”
If the logic module detects a voltage outside the normal range (0.04 to 4.96 volts), it triggers a code 44 and the charging rate is set to 14.0 volts as a “safe” option. If the output of the sensor returns to the normal range, the logic module will return to normal operation and it will use the output from the sensor to adjust charging rates.
You say its inside the power module, then what is this spring loaded thing underneath the batt? Do you mean that is like a thermocouple and the actual sensor that converts that voltage into usable signal is in the SMEC.
Last edited by rustytierod; Apr 18, 2011 at 10:20 PM.
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Member
Joined: Aug 2010
Posts: 131
Likes: 0
From: Riverside County
Year: 1991
Model: Cherokee
Engine: 4.0 litre
Hmm.
14.4 is a standard voltage for charging a 12 V Wet cell battery. So far we are inline here.
This external thermocouple is new to me for monitoring a battery. Direct voltage and amperage readings seem a better gauge to judge a battery.
Got to say, it sounds like snake oil to me. I would try to find the fastest way to over-ride/bypass that sensor I could, if it were me.
The battery temperature sensor reacts to different temperatures by producing a voltage between .04 volts and 4.96 volts DC, based on an input voltage of 5 volts DC. Because the logic module is so close to the battery, these readings can be used to estimate the temperature of the battery itself. Knowing the temperature of the battery is important because batteries are sensitive to heat, and the logic module will reduce the power sent to the battery by the alternator to prevent “cooking the battery.”
If the logic module detects a voltage outside the normal range (0.04 to 4.96 volts), it triggers a code 44 and the charging rate is set to 14.0 volts as a “safe” option. If the output of the sensor returns to the normal range, the logic module will return to normal operation and it will use the output from the sensor to adjust charging rates.
If the logic module detects a voltage outside the normal range (0.04 to 4.96 volts), it triggers a code 44 and the charging rate is set to 14.0 volts as a “safe” option. If the output of the sensor returns to the normal range, the logic module will return to normal operation and it will use the output from the sensor to adjust charging rates.
This external thermocouple is new to me for monitoring a battery. Direct voltage and amperage readings seem a better gauge to judge a battery.
Got to say, it sounds like snake oil to me. I would try to find the fastest way to over-ride/bypass that sensor I could, if it were me.
CF Veteran
Joined: Jan 2012
Posts: 3,170
Likes: 312
From: Australia
Year: 1997 (RHD)
Model: Cherokee (XJ)
Engine: 4.0 ltr
Yep, this thing does exist. Its real. Not hear-say. It's out there and we might as well face it.
I only found out when removing my batt one day and found this little disk-like thing in the tray....that had wiring to/from it, so looked into that. Mine does not have the spring in it, it just lays in its 'hole', so not sure what it actually measures like that (not pushed to battery), in my case more the ambient temp hehe
I only found out when removing my batt one day and found this little disk-like thing in the tray....that had wiring to/from it, so looked into that. Mine does not have the spring in it, it just lays in its 'hole', so not sure what it actually measures like that (not pushed to battery), in my case more the ambient temp hehe
Seasoned Member
Joined: Dec 2009
Posts: 387
Likes: 2
From: Colorado
Year: 1997
Model: Cherokee
I must have one in my `97 because I still have the OEM battery working just fine. By my tally, that's sixteen years and counting.
Dropping the voltage from 14.4 to 14 under high temp conditions would have a small, but apparently significant effect. Who'd thunk that computer was good for something other than causing headaches.
