What is the sensor under the battery pan? - JeepForum.com
 
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post #1 of 11 Old 02-07-2014, 10:46 AM Thread Starter
D0T-C0M
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What is the sensor under the battery pan?

Out of curiosity What is the sensor that sits in the battery pan right under the battery?

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post #2 of 11 Old 02-07-2014, 10:47 AM
Red Rubicon
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Battery temp sensor.
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post #3 of 11 Old 02-07-2014, 10:58 AM Thread Starter
D0T-C0M
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Really what does it do? LOL I mean why would they monitor battery temps? And what does it do if it detects an abnormal temperature?
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post #4 of 11 Old 02-07-2014, 11:36 AM
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The reason for that sensor is to regulate the alternator charge rate (the voltage regulator monitors that sensor) depending on battery temp. If it gets too hot the charge rate needs to decrease or the battery can overheat & damage it. If you have ever noticed how hot a battery gets when it is being charged off a battery charger, especially a “fast charge” you will understand. Also battery voltage drops in cold temps so the alternator will charge more if the battery temp is low.
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post #5 of 11 Old 02-08-2014, 08:22 AM
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And if you take it out, You'll throw an engine code.
Ask me how I know? LOL
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post #6 of 11 Old 02-08-2014, 09:59 AM
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Quote:
Originally Posted by Dirt22 View Post
And if you take it out, You'll throw an engine code.
Ask me how I know? LOL
You'll also only charge at 25% without a battery temp signal.
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post #7 of 11 Old 02-08-2014, 08:47 PM
Knuckelhead
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Quote:
Originally Posted by Rubi4MyMrs View Post
The reason for that sensor is to regulate the alternator charge rate (the voltage regulator monitors that sensor) depending on battery temp. If it gets too hot the charge rate needs to decrease or the battery can overheat & damage it. If you have ever noticed how hot a battery gets when it is being charged off a battery charger, especially a “fast charge” you will understand. Also battery voltage drops in cold temps so the alternator will charge more if the battery temp is low.
And if you tie the sensor back into the harness it will charge normally as if the battery isn't overheating, like when you use a AGM battery.

I've been running my duel Optima battery setup that way for over 8 years...
From the OEM FSM:
BATTERY TEMPERATURE SENSOR
DESCRIPTION
The Battery Temperature Sensor (BTS) is attached
to the battery tray located under the battery.
OPERATION
The BTS is used to determine the battery temperature
and control battery charging rate. This temperature
data, along with data from monitored line
voltage, is used by the PCM to vary the battery
charging rate. System voltage will be higher at colder
temperatures and is gradually reduced at warmer
temperatures.
The PCM sends 5 volts to the sensor and is
grounded through the sensor return line. As temperature
increases, resistance in the sensor decreases
and the detection voltage at the PCM increases.
The BTS is also used for OBD II diagnostics. Certain
faults and OBD II monitors are either enabled
or disabled, depending upon BTS input (for example,
disable purge and enable Leak Detection Pump
(LDP) and O2 sensor heater tests). Most OBD II
monitors are disabled below 20F.
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post #8 of 11 Old 02-08-2014, 08:59 PM Thread Starter
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Thanks for the very detailed answer.
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post #9 of 11 Old 02-08-2014, 09:19 PM
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Quote:
Originally Posted by Knuckelhead View Post
And if you tie the sensor back into the harness it will charge normally as if the battery isn't overheating, like when you use a AGM battery.

...
I recently installed a DieHard Platinum AGM battery. Am I reading correctly that I should move my temp sensor?

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post #10 of 11 Old 02-08-2014, 10:21 PM
Knuckelhead
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Quote:
Originally Posted by jjvw View Post
I recently installed a DieHard Platinum AGM battery. Am I reading correctly that I should move my temp sensor?
You can do that, but I don't think it will make a difference... IMO
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post #11 of 11 Old 02-08-2014, 10:26 PM
Jrob05
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I still wonder why I don't have one with an '06.
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