JLUR battery flatlining when flat towing

CoolTech

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I've re-read this thread... and remain very troubled that a couple of you are having problems keeping the battery charged during long tows. This shouldn't be a problem - even with the twin battery system of the new JL's. It is admittedly perplexing to read paulrubin3's account of being able to walk away from the Jeep for ~40 minutes and then have it start. It is almost as if the two batteries are "normalizing" - but the question would be why aren't they "normalizing" all the time? In other words, what is triggering the "normalizing". That conundrum aside, let's review some basic facts/suggestions provided in the spirit that they may help us to get to the bottom of this!

1. For towing; transfer case in neutral; Ignition key/button in OFF position
2. Regardless what light harness solution you are using - ours (Cool Tech LLC), or another, the power for the lights comes from the tow vehicle.
3. Many (most?) of the aux braking systems WILL use the Jeep's on-board battery(s) to power the aux braking device.
4. If you are using one of these Aux Braking systems, you should have a provision to charge the Jeep's battery (e.g., RVi Toad Charger)
5. MAKE SURE the charging solution is working! At the connection to the Jeep's battery with the tow vehicle OFF, the voltage should be ~12.5-~12.8v. When you start the tow vehicle (Jeep remains off), the voltage at this connection should now show ~13.5-14.2V.

All of that said, I have an educated guess as to what is causing this problem for a few of you.

The new JL (and JT Gladiators) are designed to "go to sleep", ~2-4 minutes AFTER the ignition is off, and the last door is closed. To convince yourself, try this simple test. With the Jeep in the OFF position, depress the brake pedal and notice that the rear brake lights still function. Leave the Jeep's driver's side window down, get out and shut the door. Wait 3-4 minutes and then reach in through the window and use a broom handle to depress the brake pedal. The brake lights will NOT illuminate. The Jeep is in a SLEEP state and the battery should be fine for 3-4 WEEKS or more in this state (very minimal current draw). As soon as you open a door, the Jeep exits this SLEEP state and is in a READY state... where it is drawing a lot more power as it believes it will be called upon to start. (Shutting the door again and waiting 3-4 minutes will cause the Jeep to go back to SLEEP state... - you can verify with the broom handle.)

Onthego said something in a previous post that bothered me. He said that he has a (light) indicator on the dash that confirms the Jeep's brake pedal has been activated by the aux braking device. However, the Jeep SHOULD NOT be providing a 12v brake switch indication when it is in SLEEP state (remember our broom handle test).

My theory is that there's something in the way that the aux braking devices are being wired that is not allowing the Jeep to stay in SLEEP state and it is instead in a power consumptive READY state. In turn, this constant READY state is draining the battery. The theory is easy enough for any of you to test. Try the broom handle on the brake pedal test with the Jeep disconnected from the tow vehicle - just so you know how long to wait, etc. Now, with the Jeep connected and the tow vehicle running, once again perform the broom handle test. If the rear brake lights of the Jeep work, you have a problem.

Can one of you with this problem give this a try and see if my theory has got any legs?





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roaniecowpony

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I also have the Push Button start and when I press it for Off, the small display stays on, but only for about 30 seconds, then goes off.
Exactly. I first saw the main driver's display lit and was worried. After about 30-60 secs, it went out. I think if you open a door or excercise the FOB lock/unlock the driver's display will light again. I'm 900 miles from home now and have been flat towing my jeep with no charge system and the RVI brake and Mopar Flat Tow Harness. I had to disconnect the RVI brake after 500 miles because it went wacko, but the battery was still strong when I arrived at my destination. I have a new RVI brake and it appears to be working, so if it works thru the trip home, it's going to be about 15-18 hours of towing over 2-3 days without starting the jeep. Of course, on remote highways, the brakes rarely get touched. More in a week or two when I head home.
 

roaniecowpony

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My theory is that there's something in the way that the aux braking devices are being wired that is not allowing the Jeep to stay in SLEEP state and it is instead in a power consumptive READY state. In turn, this constant READY state is draining the battery. The theory is easy enough for any of you to test. Try the broom handle on the brake pedal test with the Jeep disconnected from the tow vehicle - just so you know how long to wait, etc. Now, with the Jeep connected and the tow vehicle running, once again perform the broom handle test. If the rear brake lights of the Jeep work, you have a problem.

Can one of you with this problem give this a try and see if my theory has got any legs?
If my Jeep is connected to the tow vehicle with the tow vehicle running, it will have brake light power from the tow vehicle. I have the Mopar flat tow harness. I expect it to have brake lights in this scenario.

Edit: my error. My jeep would not/should not have brake lights by depressing the Jeep pedal, since the Mopar harness physically disconnects the connection of the lights from the Jeep circuitry. There should be no way for the Jeep power system to energize the tail lights unless a relay in the Mopar flat tow harness is not working properly.
 

paulrubin3

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I know one of the things I"m going to monitor on my next long tow is whether the Jeep is in ACC or OFF. I noticed that when I hooked up the jeep for a short (90 miles) tow last weekend home from the motorhome dealer (routine service stuff) the Jeep didn't go into OFF mode and that could have something to do with the transaxle in neutral and transmission in P. I literally had to turn the car back on and then off again and this time it went to OFF. I can't honestly say I'm 100% sure it's always been OFF when towing since the screens stay on a bit either way. I'm going to add this to my checklist to be 100% sure. I won't be towing again til probably February but those are likely to be consecutive 400 mile tow days with the Jeep likely staying connected in a pull through site. I also picked up a highly rated (about $90) lithium jump starter so if the problem does recur, I can simply attach that and perhaps 40 minutes might become 15 minutes and less noticeable. But clearly the auxiliary battery is getting back up to minimal levels during that 40 minute process. I'm also planning to bring it to the installer but he basically says there's not a lot at the charging end going on and that method of seeing if the voltage goes up to mid 13's to low 14's from 12's with the motorhome running and the Jeep off, that should answer the question as to whether the Jeep is getting charged while driving. Hadn't thought to check that myself. I just need to find something to measure that. Given that it never happens when towing isn't involved, I am seriously thinking it's user error and the Jeep isn't really OFF but rather in ACC. Never even noticed that the ring around the push button tells you.
 

Jimac

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I know one of the things I"m going to monitor on my next long tow is whether the Jeep is in ACC or OFF. I noticed that when I hooked up the jeep for a short (90 miles) tow last weekend home from the motorhome dealer (routine service stuff) the Jeep didn't go into OFF mode and that could have something to do with the transaxle in neutral and transmission in P. I literally had to turn the car back on and then off again and this time it went to OFF. I can't honestly say I'm 100% sure it's always been OFF when towing since the screens stay on a bit either way. I'm going to add this to my checklist to be 100% sure. I won't be towing again til probably February but those are likely to be consecutive 400 mile tow days with the Jeep likely staying connected in a pull through site. I also picked up a highly rated (about $90) lithium jump starter so if the problem does recur, I can simply attach that and perhaps 40 minutes might become 15 minutes and less noticeable. But clearly the auxiliary battery is getting back up to minimal levels during that 40 minute process. I'm also planning to bring it to the installer but he basically says there's not a lot at the charging end going on and that method of seeing if the voltage goes up to mid 13's to low 14's from 12's with the motorhome running and the Jeep off, that should answer the question as to whether the Jeep is getting charged while driving. Hadn't thought to check that myself. I just need to find something to measure that. Given that it never happens when towing isn't involved, I am seriously thinking it's user error and the Jeep isn't really OFF but rather in ACC. Never even noticed that the ring around the push button tells you.
I have flat towed 2018 JLR for thousands of miles with Blue Ox system with no such problems JLR always starts

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JimN

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OK, I am the ?Proud? owner of a 2018 JL Sahara with the 2.0e. We have an AirForce One brake installed. I tow behind my Diesel Motorhome. The AF1 requires not power to work except for arguably the LED Indicator light. The tail, running and brake lights are all powered off the coach with a diode as our JL has the LED lights. We started towing in 2019 and towed quite a number of times, but all were under maybe 5 hours as with Covid we were not taking any longer trips. Our first trip this year we left home, towed about 3 hours, unhooked to park, no issues, drove the Jeep around, maybe running 1-2 hours, no issues. We then left this location, drove about an hour, parked for the night, disconnected to park, no issues. Reconnected in the morning, drove about 600-700 miles over two days, did not disconnect or start the Jeep. Arrived at our stop, had to disconnect, DEAD Battery, got a jump start, all good, thought I had maybe not made sure the ignition was off and had somehow left it in ACC. Anyway, we towed another 4 hours, parked, disconnected, no issues, the Jeep then sat for for several periods of up to 3 days without being driven. We hooked up and drove about 6 hours to our first night, no issues, I specifically checked the ignition, started it, no issues. Next morning we left for about a 7 hour drive, go there, STONE COLD DEAD!

Jeep Customer Care called me about a survey I had completed, they suggested I take it in to a dealer. USELESS! They are not listening. I told them repeatedly that it has sat for 3 or more days, no issues, but this only occurs when towing. So, I am getting it back and will get a battery load test at Autozone. I have since installed a Charge line with a Diode. This is a simple 12v connection, not a specific trickle charger or anything else, just a #10 wire and a diode. It will handle up to 30 amps.

What has anyone else found? This is BS! If I had an electric brake system that was powered off the vehicle battery I would understand, been there with my Liberty, original install oof a Unified Brake, the installer did not connect a charge line, it was good for about a 6 hour tow, then it would die. The AF-1 doesn't draw, the lights are LED and also are powered off the RV, OK, the brake lights MAYBE draw since the brake peddle is activated when braking, but they are two LEDs! The Tail lights are on, but they are powered by the RV line.

OK, thanks for letting me rant here a bit. I appreciate any info you all might have.
 

JimN

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I've re-read this thread... and remain very troubled that a couple of you are having problems keeping the battery charged during long tows. This shouldn't be a problem - even with the twin battery system of the new JL's. It is admittedly perplexing to read paulrubin3's account of being able to walk away from the Jeep for ~40 minutes and then have it start. It is almost as if the two batteries are "normalizing" - but the question would be why aren't they "normalizing" all the time? In other words, what is triggering the "normalizing". That conundrum aside, let's review some basic facts/suggestions provided in the spirit that they may help us to get to the bottom of this!

1. For towing; transfer case in neutral; Ignition key/button in OFF position
2. Regardless what light harness solution you are using - ours (Cool Tech LLC), or another, the power for the lights comes from the tow vehicle.
3. Many (most?) of the aux braking systems WILL use the Jeep's on-board battery(s) to power the aux braking device.
4. If you are using one of these Aux Braking systems, you should have a provision to charge the Jeep's battery (e.g., RVi Toad Charger)
5. MAKE SURE the charging solution is working! At the connection to the Jeep's battery with the tow vehicle OFF, the voltage should be ~12.5-~12.8v. When you start the tow vehicle (Jeep remains off), the voltage at this connection should now show ~13.5-14.2V.

All of that said, I have an educated guess as to what is causing this problem for a few of you.

The new JL (and JT Gladiators) are designed to "go to sleep", ~2-4 minutes AFTER the ignition is off, and the last door is closed. To convince yourself, try this simple test. With the Jeep in the OFF position, depress the brake pedal and notice that the rear brake lights still function. Leave the Jeep's driver's side window down, get out and shut the door. Wait 3-4 minutes and then reach in through the window and use a broom handle to depress the brake pedal. The brake lights will NOT illuminate. The Jeep is in a SLEEP state and the battery should be fine for 3-4 WEEKS or more in this state (very minimal current draw). As soon as you open a door, the Jeep exits this SLEEP state and is in a READY state... where it is drawing a lot more power as it believes it will be called upon to start. (Shutting the door again and waiting 3-4 minutes will cause the Jeep to go back to SLEEP state... - you can verify with the broom handle.)

Onthego said something in a previous post that bothered me. He said that he has a (light) indicator on the dash that confirms the Jeep's brake pedal has been activated by the aux braking device. However, the Jeep SHOULD NOT be providing a 12v brake switch indication when it is in SLEEP state (remember our broom handle test).

My theory is that there's something in the way that the aux braking devices are being wired that is not allowing the Jeep to stay in SLEEP state and it is instead in a power consumptive READY state. In turn, this constant READY state is draining the battery. The theory is easy enough for any of you to test. Try the broom handle on the brake pedal test with the Jeep disconnected from the tow vehicle - just so you know how long to wait, etc. Now, with the Jeep connected and the tow vehicle running, once again perform the broom handle test. If the rear brake lights of the Jeep work, you have a problem.

Can one of you with this problem give this a try and see if my theory has got any legs?
I will give this a try, but wiht an AirForce One Brake is it AIR operated, not electric, so at most there is a minor draw for the LED indicator and perhaps for the tail lights IF they are powered with the ignition off. They are connected via a diode to the RV lights.
 

JimN

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I will give this a try, but wiht an AirForce One Brake is it AIR operated, not electric, so at most there is a minor draw for the LED indicator and perhaps for the tail lights IF they are powered with the ignition off. They are connected via a diode to the RV lights.
OK, I just got back from the dealer. THey could not find any issue except a minor elevation of parasitic draw. AF-1 draws no power. SO I parked, opened the window, closed the door, the Jeep is NOT connected to the RV. I waiteed until the lights all went out plus another couple minutes, got a stick, pressed the brake peddle and the lights work. SO, where is this documented that the lights don't work unless the key is on? That does not seem right. My next trick will be to pull the MH out, hook up the air line, but not the umbilical and see what happens. DO the brake lights work when I hit the RV Brakes? Don't know what to do after this. I have added a charge line.
 

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I have the BlueOx flat tow system and CoolTech flat tow wiring system. It includes a trickle charger. I've never had an issue in two years and 25K+ flat towing.
 

JimN

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I have the BlueOx flat tow system and CoolTech flat tow wiring system. It includes a trickle charger. I've never had an issue in two years and 25K+ flat towing.
What brake system do you have? We have an AirForce One, never had an issue until this year. I ded add a charge line. I may upgrade to a Toad Charger.
 

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BlueOx Patriot and the power for it plugs into a cigarette socket drivers side. The CoolTech wiring system has a harness the keeps the plug always hot and a trickle charger powdered from my tow vehicle keeps the toad batteries up. My tow vehicle has 2 motor batteries and 4 house batteries. never had a problem in two years towing.
 

JimN

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BlueOx Patriot and the power for it plugs into a cigarette socket drivers side. The CoolTech wiring system has a harness the keeps the plug always hot and a trickle charger powdered from my tow vehicle keeps the toad batteries up. My tow vehicle has 2 motor batteries and 4 house batteries. never had a problem in two years towing.
I see, my previous system was electric, the AF-1 is not.
 

JJT-NC

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OK, I just got back from the dealer. THey could not find any issue except a minor elevation of parasitic draw. AF-1 draws no power. SO I parked, opened the window, closed the door, the Jeep is NOT connected to the RV. I waiteed until the lights all went out plus another couple minutes, got a stick, pressed the brake peddle and the lights work. SO, where is this documented that the lights don't work unless the key is on? That does not seem right. My next trick will be to pull the MH out, hook up the air line, but not the umbilical and see what happens. DO the brake lights work when I hit the RV Brakes? Don't know what to do after this. I have added a charge line.
@JimN I am in the same boat as you. I've done the test and it proves that with the Jeep off, it wakes up mechanical brake activation. At least. My dealership was very frank about battery issues on these jeeps and the fact that they never turn off.

I am trying to resist adding a charger, but this seems to be the popular response by many. I would rather fix this problem at the source. I am looking high and low for a battery disconnect solution that is quick and idiot proof. ;-) I am having trouble finding one, but then again I am the idiot!!
 

JimN

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@JimN I am in the same boat as you. I've done the test and it proves that with the Jeep off, it wakes up mechanical brake activation. At least. My dealership was very frank about battery issues on these jeeps and the fact that they never turn off.

I am trying to resist adding a charger, but this seems to be the popular response by many. I would rather fix this problem at the source. I am looking high and low for a battery disconnect solution that is quick and idiot proof. ;-) I am having trouble finding one, but then again I am the idiot!!
Well, while I agree, one probmem if you have a total disconnect is that your EConnect will also flatline. I just added a #10 wire from the plug to the large battery positive. I also installed a 30 amp diode to keep it one way. Had similar in my Jeep Liberty. That one was SUPPOSED to have it all done by the installer as the brake was electric. They wired the Jeep, but forgot to check the RV! Half way between NJ and Tulsa I started getting warnings, I had one spare day there that I spent chasing down teh parts I needed to install a 12v line in the RV. This time its the reverse! I am going to add a 20 amp fuse in the circuit. No way I should need any more than a trickle charge. But I am wondering, what if I installed a 'brake light kill switch? Break the line on the brake light switch and put a toggle in?? If that is the issue, the Jeep 'wakes up' when the brake switch is activated, maybe that would solve the issue??? Thoughts.
 

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