xeon
Well-Known Member
- First Name
- John
- Joined
- Jan 18, 2018
- Threads
- 13
- Messages
- 332
- Reaction score
- 250
- Location
- California
- Vehicle(s)
- JLU Rubicon
- Thread starter
- #1
I have a 2018 JLUR and have replaced the main and aux battery three times so far. I just crossed 60,000 miles. During the first few years of ownership, I used it to commute to work but now I am lucky to put 3000 miles on it a year. So it sits in the garage a lot waiting for its next adventure. During the past year, I started to notice that my alternate would be maxing out during every drive (pegged at 14.5V) as it tried to charge the batteries. My MPG in the city was nothing unusual 15.5 to 16 MPG city, 19 to 20 MPG highway. The annoying thought of having to replace the batteries again made me pull the plug and purchase a Noco10 and then a Noco5. Both work great...the 5 is just that much easier to mount and I don't need the speed of the 10 since my JLUR sits so long.
After letting the battery get a complete charge things with the Jeep started working differently. I noticed the alternator did not fully engage during any of my short trips. Instead of the full load of 14.5+ I would see trickles at 12.5 to 12.7. I didn't think much of it other than the battery is charged and all is good.
However, in longer trips 100 miles plus on the highway I noticed something very different. Where I normally get 19 to 20 MPG (35" K02s at 34 psi, automatic trans, cruising between 65 and 75) I am now getting between 24 and 26 mpg. Why the big jump? Of course, I was skeptical. Maybe it was the truck I was behind for a long time on that first time out.
After a few tests. I am consistently between 24 and 26 mpg on the highway when the battery has been fully charged and the alternator does not seem to be doing much of anything. If I do not charge the jeep and take it out...the alternator is constantly charging the battery pumping out 13.3 to 14.5 volts and when this occurs I am getting the typical 19 to 20 MPG.
I honestly can't figure out why the big difference. I am guessing it's the alternator drag. I am hoping others here that use a battery maintainer can chime in and let me know what they are experiencing. Maybe my alternator is just a "drag" and it needs to be replaced. Not sure. Any other thoughts on this would be greatly appreciated. For the next few tests, I am going to assume the onboard computer that is calculating the MPG is drastically off. I use it more as a gauge of normalcy vs accuracy but now I have to question that too.
After letting the battery get a complete charge things with the Jeep started working differently. I noticed the alternator did not fully engage during any of my short trips. Instead of the full load of 14.5+ I would see trickles at 12.5 to 12.7. I didn't think much of it other than the battery is charged and all is good.
However, in longer trips 100 miles plus on the highway I noticed something very different. Where I normally get 19 to 20 MPG (35" K02s at 34 psi, automatic trans, cruising between 65 and 75) I am now getting between 24 and 26 mpg. Why the big jump? Of course, I was skeptical. Maybe it was the truck I was behind for a long time on that first time out.
After a few tests. I am consistently between 24 and 26 mpg on the highway when the battery has been fully charged and the alternator does not seem to be doing much of anything. If I do not charge the jeep and take it out...the alternator is constantly charging the battery pumping out 13.3 to 14.5 volts and when this occurs I am getting the typical 19 to 20 MPG.
I honestly can't figure out why the big difference. I am guessing it's the alternator drag. I am hoping others here that use a battery maintainer can chime in and let me know what they are experiencing. Maybe my alternator is just a "drag" and it needs to be replaced. Not sure. Any other thoughts on this would be greatly appreciated. For the next few tests, I am going to assume the onboard computer that is calculating the MPG is drastically off. I use it more as a gauge of normalcy vs accuracy but now I have to question that too.
Sponsored