Battery Temp Sensor question

[01_Cummins_4x4]

I've been really busy working on my 01 Dodge Ram 2500 Cummins 4x4. Friday night after work - pull the HVAC box out and replace the heater and evaporator cores. The heater core was the original brass one from the factory, but it was plugged internally. The previous owner just installed a new radiator and I just replaced the water pump about 3 weeks ago. Vacuumed down the A/C system last night, and then recharged it with freon.

 

Yesterday - changed engine oil and filter, install PCM protection mod with soldering in an inline fuse and using a 5A fuse, modify the charging system with the W-T ground mod, install a 150A circuit breaker to protect alternator.

 

What are we supposed to do about the battery temp sensor after doing the W-T Ground mod?

[Threadzy]

Nothing I’m aware of. I added an additional 2ga ground cable connecting the batteries. Some say it’s not needed with a stock amp alternator. I haven’t had any issues. 

[JAG1]

I asked this question to W-T on the Telephone. He says to do the added parallel wires is best and as for the temp sensor you can run the B+ charging wire from the alternator to the drivers side battery where the sensor is. Routing is important not to get in the same run or close to other wires. RF noise interference something playing havoc with sensors and electronics. I'm going to reroute to the drivers battery with heavier cable since it's a longer run to the drivers battery using Marine tinned and braided wire. I think I have number 6 wire already in the shop for this.

[Mopar1973Man]

Nothing... Battery temp sensor stay right where its at. The battery are already tied together. If both batteries are healthy then both batteries should be the same temperature. 

 

Again like my solar/hydro system is eight deep cycle 6V batteries and only 1 temp sensor. Again if all the batteries are healthy they will be all the same. 

[JAG1]

Then why did I have a shorted passenger battery telling the alternator to hammer it with everything the alternator has got, eventually toasting the alternator? The temp sensor should have told the charge to slow down or go into reduced amperage. It was my fault not changing batteries after the short was found in the passenger battery. You know....... as long as it starts.... what the heck get all you can out of these old batteries, That was wrong for me to do that.

 

This for Michael Nelson......

Edited January 31, 2021 by JAG1

[LorenS]

On 1/31/2021 at 1:53 PM, JAG1 said:

Then why did I have a shorted passenger battery telling the alternator to hammer it with everything the alternator has got, eventually toasting the alternator?

 

On 1/31/2021 at 1:17 PM, Mopar1973Man said:

If both batteries are healthy

I guess that's the big, bold, italicized, capital letters, underlined "IF".

[JAG1]

54 minutes ago, LorenS said:

 

I guess that's the big, bold, italicized, capital letters, underlined "IF".

 

54 minutes ago, LorenS said:

 

I guess that's the big, bold, italicized, capital letters, underlined "IF".

Yes, that is what I'm saying LorenS, that the battery temp sensor didn't pick up on the heat, should have been able to signal the PCM  telling the alternator to back off, not burn itself out. That's why W-T says to run the B+ wire to the battery that has the sensor.... Mopar Man says no..... W-T says to do it.  What's sensor for if it cannot send  a message to limit output ?

 

I got the copper the lugs today for this change.

Edited February 3, 2021 by JAG1

[Tractorman]

I think that there is some misunderstanding regarding the purpose of the battery temperature sensor.  The following is my understanding of how the charging system works:

 

The battery temperature sensor is there to determine  the target upper limit voltage of the charging system based on the temperature of the battery. By regulating the upper limit voltage (target voltage) at different values for different ambient temperatures, it gives a longer life span for the batteries.   The battery temperature sensor does not control alternator output voltage at any time when the electrical load drops below the target voltage.

 

Example:

 

It's a hot day.  The battery temperature sensor dictates target voltage to be 13.8 volts.

 

@JAG1has wired his alternator output wire to the driver side battery because WT said so.... just kidding here.

 

The passenger side battery has a shorted cell that is drawing 50 amps.  The rest of the electrical load is 25 amps - a total of 75 amps. Charging voltage will fall below the targeted 13.8 volts and the internal voltage regulator in the PCM will tell the alternator to pick up the pace and put out whatever amperage is necessary to reach the target voltage of 13.8 volts.  In this case the alternator will need to charge continuously at the 75 amp rate.

 

So, moving the alternator output wire to the driver side battery does not help in this scenario.  As @Mopar1973Man has said many times...., the batteries and electrical connections have to be in good operating condition so the charging system can operate properly.

 

Demanding that the battery temperature sensor should be able to protect the alternator is akin to saying that the engine thermostat should be able to protect the engine when the radiator is plugged. or the water pump has stopped turning.

 

- John

[Mopar1973Man]

Correct. @Tractorman

 

Battery temp sensor isn't design for detecting shorted cells. Only to set the maximum charge voltage. Colder the temperature the higher the level goes. The warmer the battery the lower it goes. I've seen from 13.2 to 14.8 volts as a range. Battery temp sensor will not protect anything. 

 

Even in @JAG1case there is no way to stop a shorted battery from getting hot and drawing more current. No matter what battery had the sensor the only thing is might of had a weak battery in the morning (sensing high battery temp) or in his case sensing the cooler battery and boil the electrolyte out of the shorted battery.  Either way its not the battery temp sensor job it the owners job to replace the bad batteries (as a set) and then clean and test his terminals. Again battery temp sensor will not protect alternators or batteries just sets the voltage based on temperature. 

[LorenS]

I guess I'm having a hard time understanding how if the temp sensor was on the bad battery it wouldn't have helped in JAG1's case.  Would not the huge short generate lots of heat?  Wouldn't the increase in temp throw cause the PCM to reduce charging?  Of course it's 50/50 odds that you have the sensor on the correct battery.  I have forgotten most of the story behind that alternator failure, however.

[Mopar1973Man]

Just now, LorenS said:

I guess I'm having a hard time understanding how if the temp sensor was on the bad battery it wouldn't have helped in JAG1's case.

 

It won't. Being if the hot battery was being monitor now the charge voltage would of drop super low and undercharged the battery and being its a shorted cell it would of created  less charging voltage and left with weak starting batteries. Battery temp sensor is ONLY for setting the charge voltage NOT to protect from runaway charging with bad batteries. Again it only sets the charging voltage base on battery temperature. It is not used as a fail safe to prevent boiling over a shorted cell battery. Again this system is design for maintaining proper voltage for charging based ON WEATHER. Cold winter days require more charging voltage to get the battery up to temp to charge properly. Then in hot summers reduce the battery temperature to prevent boiling over. The old Mopar External regulator was based on under hood temperature this was used from the early 60's to early 90's. These little regulator boxes where mounted in special location to detect under temperatures but the system was flawed and typically boiled batteries over and then in the summer when overheating the engine would under charge. This was updated in the modern system to detect only 1 battery being both battery are bound together. Being cell temperatures can vary from one battery to the other it up to the owner to replace batteries as a pair, inspect cables that have excessive voltage drop and test batteries separately. 

 

Again battery temperature sensor is NOT to protect against shorted cell batteries. 

 

Cell that shorted out is because the lead plate start to sulfate and the debris piles up in the bottom of the battery now shorting the cell plates out. Now if @JAG1was doing his equalizing charge on the batteries then the that sulfation would of been pull back into the plates and saved the batteries.  It's not the temperature sensor job to do this either. Again it only sets the charge voltage to what the battery temperature is. 

[Doubletrouble]

2 minutes ago, Mopar1973Man said:

Now if @JAG1was doing his equalizing charge on the batteries then the that sulfation would of been pull back into the plates and saved the batteries.

 This is a process that still eludes me. I understand it to a point but not fully. I have looked a "special" battery chargers that claim to rejuvenate batteries but not sure if that is what's needed to do the job. I have tested both of my batteries before winter set in and they tested good. I then charged them separately to a full charge. Is this near what you describe? Forgive the ignorance on this. 

[Mopar1973Man]

Ok. 

 

Equalizing Batteries you want to reach 15.5 to 15.7 Volts and the battery need to be charged outside or open air. They do boil at this point. Now continue to charge till the charge amps drop to near zero. This should be completed. Like I cheat and just use jump cables and hook the battery to my solar system and let it ride with inverter during the equalize charge. My system is set to run for 2 hours at 31.0 Volts for 24V battery bank. Hooking up as a 12V battery to the bank it will typically show about 15.5 to 15.7 Volts and all the batteries are boiling. Now afterwards check your electrolyte levels and return the battery to service. 

 

As from Battery University...

Quote

Stationary batteries are almost exclusively lead acid and some maintenance is required, one of which is equalizing charge. Applying a periodic equalizing charge brings all cells to similar levels by increasing the voltage to 2.50V/cell, or 10 percent higher than the recommended charge voltage. 

An equalizing charge is nothing more than a deliberate overcharge to remove sulfate crystals that build up on the plates over time. Left unchecked, sulfation can reduce the overall capacity of the battery and render the battery unserviceable in extreme cases. An equalizing charge also reverses acid stratification, a condition where acid concentration is greater at the bottom of the battery than at the top.

Experts recommend equalizing services once a month to once or twice a year. A better method is to apply a fully saturated charge and then compare the specific gravity readings (SG) on the individual cells of a flooded lead acid battery with a hydrometer. Only apply equalization if the SG difference between the cells is 0.030.

During equalizing charge, check the changes in the SG reading every hour and disconnect the charge when the gravity no longer rises. This is the time when no further improvement is possible and a continued charge would have a negative effect on the battery.

The battery must be kept cool and under close observation for unusual heat rise and excessive venting. Some venting is normal and the hydrogen emitted is highly flammable. The battery room must have good ventilation as the hydrogen gas becomes explosive at a concentration of 4 percent.

Equalizing VRLA and other sealed batteries involves guesswork. Observing the differences in cell voltage does not give a conclusive solution and good judgment plays a pivotal role when estimating the frequency and duration of the service. Some manufacturers recommend monthly equalizations for 2–16 hours. Most VRLAs vent at 34kPa (5psi), and repeated venting leads to the depletion of the electrolyte, which can lead to a dry-out condition.

Not all chargers feature equalizing charge. If not available, the service should be performed with a dedicated device.

 

Edited February 3, 2021 by Mopar1973Man

[Doubletrouble]

 I would have to look for a battery equalizer/charger then correct? 

 I'm interested because I have lots of batteries. 2 in the truck, 2 in the camper, 1 in the grain truck, 2 riding mowers and 6 tractors and a combine. That's alot of batteries to replace, they aren't cheap.

[Mopar1973Man]

Yup. Charger with equalize mode are not cheap. Try not to get any automatic chargers they don't seem to work all that good. I've used a few automatic chargers most shut down too fast. Hence why I like my time base charger off the inverter.

 

My Trace Inverter in Equalize mode on a 24V battery bank.

 

Look close the batteries started to boil. This is normal and the rotten egg smell too. Hydrogen gas will be created. Oh look at the cables these are 25 YEARS OLD. No corrosion, no rotten leads. Hmmm...  Engine oil is a wonderful corrosion prevention. 

 

This battery bank cost me $4,800 dollars to replace 10 years ago. Each battery is 125 pounds. There is a 1,000 pounds of batteries. Four 6V batteries tied as 24V in two banks. The small yellow lead is my one and only temp sensor for the batteries. As you see I tucked in between the 3rd batteries. It cannot tell what the other 6 batteries are doing for temperature either. 

Edited February 3, 2021 by Mopar1973Man

[LorenS]

3 hours ago, Mopar1973Man said:

It won't. Being if the hot battery was being monitor now the charge voltage would of drop super low and undercharged the battery and being its a shorted cell it would of created  less charging voltage and left with weak starting batteries.

Sure seems to me that it WOULD have worked. Weak starting batteries, to me, is a hell of a lot preferable to catching my alternator on fire.

[Tractorman]

3 hours ago, LorenS said:

Sure seems to me that it WOULD have worked. Weak starting batteries, to me, is a hell of a lot preferable to catching my alternator on fire.

 

Even if the output wire of the alternator is routed to the battery with the battery temperature sensor and that battery has a shorted cell, the battery temperature sensor will not stop the alternator from doing what it is commanded. 

 

From the example I gave previously:  the shorted cell demands 50 amps (this time the driver side battery), the rest of the electrical system demands 25 amps (75 amps total).  Let's say the battery temperature sensor tells the PCM to target for 13.8 volts.  At the moment the alternator will be commanded by the electronic voltage regulator inside the PCM to reach the target voltage of 13.8 volts.  To maintain that voltage, the alternator must keep delivering 75 amps.  The battery temperature begins to rise (because of the shorted cell) so the battery temperature sensor sends this information to the PCM.  The PCM decides to reduce target voltage to 13.5 volts, but nothing else has changed - the shorted cell still draws 50 amps and the remaining electrical load of 25 amps is still there, so the alternator continues to deliver 75 amps - 50 amps of unnecessary power to the shorted cell .  This cycle will likely continue until the battery temperature sensor reaches its lower limits (which would have to be above battery static voltage), or the battery reaches a point that it can dissipate heat as rapidly as it is generating heat.  But, meanwhile, the alternator will continue to do what it is commanded to do, and that is to deliver whatever amperage is needed to fulfill the target voltage.

 

If the battery temperature sensor had the ability to limit target voltage to below normal battery static voltage, then many electronic components would be compromised - much more costly than an alternator.

 

@Mopar1973Man, gives good examples of the benefits of performing equalizing charges on batteries to extend their life with his solar charging system for his house.  But equalizing charges may not be as effective with some of our truck batteries.  Not all batteries are equal when it comes to the quality of construction of the battery.  Many times the failure of older batteries is simply the infrastructure supporting the cells fails and creates open or shorted circuits.  Our trucks do not give batteries the smoothest ride.

 

Good batteries and good electrical connections are key to long lasting alternators and electronic components.

 

- John

[JAG1]

I'm trying to find out why two alternators shorted out within 4 months, I tested the grid heater relays today.  they both click when I put voltage thru the trigger wires using a 9 volt battery and some jumpers.  The click isn't as loud and definite as my first gen was also testing with the Ohm meter when they are 'off', not activated, the meter shows around 3.5 ohms on both relays. I am confused here because when off they should be showing infinite ohms resistance, right? could both be bad relays? Further testing tomorrow using 12 volts but disconnected from the grid heaters will allow use of the voltmeter when activated. I will report back.

 

Also it looks like the ohm meter is showing both previous alternators to be shorted out as well because they show around 3.5 ohms resisteance as well between the frame and the b+ charge cable stud.

 

Any thoughts are appreciated 

 

 

 

 

Edited February 4, 2021 by JAG1

[Dieselfuture]

5 hours ago, JAG1 said:

The click isn't as loud and definite as my first gen was also testing with the Ohm meter when they are 'off', not activated, the meter shows around 3.5 ohms on both relays

The click might not be as loud because you're using 9 volts. All that relay is is basically on off switch, when activated should have 0.000 ohm or very close to it, the higher the ohms indicate loose connection. When the relay is disabled (no power going to it) should be OL, if you're reading 3.5 ohms that means they're partially staying on, or so my brain tells me. 

Testing the alternator, one leed on the case one leed on the stud using ohm meter should read OL if you getting any reading then it's shorted to ground.

[Mopar1973Man]

5 hours ago, JAG1 said:

Also it looks like the ohm meter is showing both previous alternators to be shorted out as well because they show around 3.5 ohms resisteance as well between the frame and the b+ charge cable stud.

 

Diodes are junk. Shouldn't be any connection between the case and the BATT + stud. That is a short to ground. 

 

5 hours ago, JAG1 said:

I am confused here because when off they should be showing infinite ohms resistance, right?

Correct for the grid heaters relays. It should be infinite ohms on the two large studs. The two smaller studs should have a ohm reading. 

Edited February 4, 2021 by Mopar1973Man