Dead battery Jeep Trailhawk

[sheridany]

I have a 2015 Jeep Cherokee Trailhawk that I have flat towed for 2 years. I have the mopar death wobble kit installed. My original setup included the RVi braking system and I have never had an issue. Recently I decided to change to the demco AF1 system and had it installed at a hitch and tow shop. On our first trip of 450 miles, we found a dead battery on the jeep. The tech who installed the AF1 change said the existing charge line going to jeep should work fine. The jeep battery is less than 2 years old. Why am I having a dead battery now? Do I need to add a battery charger on the jeep?

[Isaac-1]

What kind of chargeline do you have installed now, many of them can't supply enough amps to keep the EPS system from draining the battery.

[Bikinjim]

The AFO system is mechanical for the normal braking function (powered by coach brake air) and only uses DC power for illumination of the brake notification light and to energize the breakaway relay during a breakaway event. So it shouldn’t be the cause for the Jeep’s dead battery if everything was installed correctly. If you previously had an adequately functioning charge line and did not have battery issues with the previous brake system system during long tows you should not have any with the AFO system. So a couple of thoughts come to mind, either the charge line was somehow rendered inoperable or degraded during the AFO installation, or the flat tow harness was left energized after towing and depleted the battery before the Jeep was attempted to be started. I would use a digital multimeter to validate that the charge line is functioning with everything connected and in tow mode by measuring > ~ 13.5 volts at the Jeep battery. You can also use a DC clamp meter to verify that the charge amps through the charge line can keep up with the Jeep’s tow mode consumption rate.

[sheridany]

Originally Posted by Bikinjim

The AFO system is mechanical for the normal braking function (powered by coach brake air) and only uses DC power for illumination of the brake notification light and to energize the breakaway relay during a breakaway event. So it shouldn’t be the cause for the Jeep’s dead battery if everything was installed correctly. If you previously had an adequately functioning charge line and did not have battery issues with the previous brake system system during long tows you should not have any with the AFO system. So a couple of thoughts come to mind, either the charge line was somehow rendered inoperable or degraded during the AFO installation, or the flat tow harness was left energized after towing and depleted the battery before the Jeep was attempted to be started. I would use a digital multimeter to validate that the charge line is functioning with everything connected and in tow mode by measuring > ~ 13.5 volts at the Jeep battery. You can also use a DC clamp meter to verify that the charge amps through the charge line can keep up with the Jeep’s tow mode consumption rate.

I was at NIRVC today and they checked the charge lines into the jeep and everything checked out. So I am wondering if it’s an operator error issue where I didn’t completely turn off the jeep Run mode or acc mode or I tried to start it as before I removed the fuse and hit the switch. Sounds like I should remove fuse and flip off switch before starting the jeep as I may have depleted battery. We are headed out again in a few weeks so we can test it out again.

[Bikinjim]

I am not sure exactly what process you are following but you should power up the flat tow harness to energize the power steering immediately before towing and then immediately power down the flat tow harness after towing (in the proper sequence with the console switch). If you don’t do that you will keep the power steering energized which will deplete the battery. Your Prevost may be like my Freightliner chassis that has a relay to energize the charge line only when the ignition switch is on. So if after towing and you turn off the coach the charge the charge line will also be off and if you don’t power off the tow harness, the Jeep battery will discharge until you do. That may not be your problem but something to consider.

[sheridany]

Originally Posted by Bikinjim

I am not sure exactly what process you are following but you should power up the flat tow harness to energize the power steering immediately before towing and then immediately power down the flat tow harness after towing (in the proper sequence with the console switch). If you don’t do that you will keep the power steering energized which will deplete the battery. Your Prevost may be like my Freightliner chassis that has a relay to energize the charge line only when the ignition switch is on. So if after towing and you turn off the coach the charge the charge line will also be off and if you don’t power off the tow harness, the Jeep battery will discharge until you do. That may not be your problem but something to consider.

I follow the same sequence every time after the Jeep is hooked to the tow bar and everything is connected, I shift the transfer case into neutral, make sure it’s in neutral, then shut down. The last steps are to release the parking brake and then energize the power steering and put the the 10 amp fuse in as the last step. I do the reverse when we want to unhook. Take fuse out, power down power steering switch in center console. Set parking brake and unhook.

[Isaac-1]

Originally Posted by sheridany

I was at NIRVC today and they checked the charge lines into the jeep and everything checked out. So I am wondering if it’s an operator error issue where I didn’t completely turn off the jeep Run mode or acc mode or I tried to start it as before I removed the fuse and hit the switch. Sounds like I should remove fuse and flip off switch before starting the jeep as I may have depleted battery. We are headed out again in a few weeks so we can test it out again.

How did they test it? Without monitoring the charge level while towing their is not an easy way to tell if the charge line is providing more power than the EPS system is drawing while the Cherokee is being towed, as the EPS is not a constant amp draw, it varies with movement of the steering system. I find on our Cherokee that our charge line is likely marginal as I get low battery voltage warnings from my braking system (which has remote in cab voltage display) when we are towing on windy roads, but seems to do fine on long mostly straight roads.

[sheridany]

Let me ask a couple of questions as we aren’t back at the bus until the end of month to hook the Jeep up in order to test the voltage coming from the bus to the Jeep ready to tow.

My DW reminded that when I went to unhook it i attempted to shift the transfer case and it wouldn’t shift. I then tried to start it without realizing I had NOT removed the fuse first and then turned off the flat tow switch. A senior moment. Would that kill the battery or cause it to not start?

Second I have two dash cams in Jeep front and rear plugged into 12 v outlets. I believe both only come on when engine is running. It makes me wonder if these are causing extra draw and they should be unplugged.

I am trying to exhaust all possibilities of “operator errors” before we go back because we are headed cross country and I’d like to know we are good to go because of my error versus something else and we have to deal with it enroute.

[Bikinjim]

Did you unhook (and remove the fuse) the Jeep immediately after you finished towing when you had the dead battery or did you wait a significant amount of time? If you did it relatively immediately, then your charge line didn’t keep up with the Jeep’s consumption. I wouldn’t think that two small dash cams would materially affect the consumption so most likely there is a fault in the charge line. It may have happened coincidentally with the brake system change or was caused by it. But my opinion is you should rule that possibility out first which will require testing with the Jeep attached to the running coach and in tow mode. You need to understand if the current flow into the battery is equal to the Jeep’s consumption and the easiest way to do that is with a DC clamp meter. Just measuring a voltage in the Jeep not connected to the coach won’t tell you the story as there can be weak connections or deficient wiring that won’t be identified until put under load. If you waited a while to remove the fuse after towing, that is most likely the cause for the dead battery (continued consumption in the Jeep without charge current from the charge line). Starting the Jeep without removing the fuse shouldn’t have affected the battery but could set codes in the Jeep’s computer.

[sheridany]

Originally Posted by Bikinjim

Did you unhook (and remove the fuse) the Jeep immediately after you finished towing when you had the dead battery or did you wait a significant amount of time? If you did it relatively immediately, then your charge line didn’t keep up with the Jeep’s consumption. I wouldn’t think that two small dash cams would materially affect the consumption so most likely there is a fault in the charge line. It may have happened coincidentally with the brake system change or was caused by it. But my opinion is you should rule that possibility out first which will require testing with the Jeep attached to the running coach and in tow mode. You need to understand if the current flow into the battery is equal to the Jeep’s consumption and the easiest way to do that is with a DC clamp meter. Just measuring a voltage in the Jeep not connected to the coach won’t tell you the story as there can be weak connections or deficient wiring that won’t be identified until put under load. If you waited a while to remove the fuse after towing, that is most likely the cause for the dead battery (continued consumption in the Jeep without charge current from the charge line). Starting the Jeep without removing the fuse shouldn’t have affected the battery but could set codes in the Jeep’s computer.

Okay makes sense. We will hook it all up when we go back and do the voltage measurement as that’s where we need to start. Thank you for your detailed response.