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Low battery message came up on dashboard after turn off my car 4 weeks ago, I used the multimeter and found the 2nd small auxiliary battery is under 8V which way under regular 12V, then I took it out and charged it with Vector 15AMP 12-volt battery charger. After a few minutes, the external battery charger went into Reconditioning mode. so I replaced it with a Diehard Powersport BTX5L battery
I ran my car engine with ac and radio on my drive way for over an hour after installation, but the low battery message light came back right after turn off the engine, I realized that my main battery went under 12V, the new auxiliary battery got 12.6V when engine is off, and it got a reading 14.6V when engine is on, Does this look like my alternator is working?
So I charged all my batteries using the external battery charger using the common terminals under the hood, did the BMS rest procedure and drove my car for 3 days, 30 miles per day. Unfortunately the main battery still loses power and the light came back. Is my BMS reset incorrect? Can BMS module be faulty? or the dealer have to reset it?
The battery "posts" under the front hood are there ONLY for hooking up a battery or charger to open the trunk. ALL recharging should be done with the charges negative clamp attached to the ground point to the body between the batteries and the plus clamp to the plus (+) posts on the batteries.
The battery "posts" under the front hood are there ONLY for hooking up a battery or charger to open the trunk. ALL recharging should be done with the charges negative clamp attached to the ground point to the body between the batteries and the plus clamp to the plus (+) posts on the batteries.
My main battery had been charged 3 times via the terminals under the hood, I also charged the battery once using its positive and negative tips under the trunk. I hope I did not damage anything. It is very weird that the 2nd battery gets higher voltage(14.6V), but the main battery keep getting lower voltage while running the engine. Is main battery charging the 2nd battery instead of the alternator?
Zuo, when the car is running, is the main battery getting the same voltage as the small battery? It should. Both batteries should be getting whatever the alternator is outputting. I was initially think you may have had the megafuse go bad, but then, you would not be able to start the car at all. So, we know the circuit between the alternator and the battery is intact.
Silly question. When you first start up the car after recharging the battery, does the car fire up right away or does it feel like the motor has to roll over for a few seconds before it catches? If the motor takes a few seconds of rolling before catching may indicate that we have a "high resistance" somewhere in the cable between the battery and the starter. Now, when I say a high resistance, I am only talking like a quarter ohm or something on that level. This is something that unless you have special diagnostic equipment, it is going to be difficult to see unless other checks are done.
Zuo, when the car is running, is the main battery getting the same voltage as the small battery? It should. Both batteries should be getting whatever the alternator is outputting. I was initially think you may have had the megafuse go bad, but then, you would not be able to start the car at all. So, we know the circuit between the alternator and the battery is intact.
Silly question. When you first start up the car after recharging the battery, does the car fire up right away or does it feel like the motor has to roll over for a few seconds before it catches? If the motor takes a few seconds of rolling before catching may indicate that we have a "high resistance" somewhere in the cable between the battery and the starter. Now, when I say a high resistance, I am only talking like a quarter ohm or something on that level. This is something that unless you have special diagnostic equipment, it is going to be difficult to see unless other checks are done.
The main battery always gets lower voltage than the second battery. The car fires up right away when fully charged by the external charger. After driving a few short trips like about 30 miles, the "low battery" message starts showing up after engine stop, "the motor has to roll over for a few seconds" to start up, and then some error pops up on dashboard while driving, main screen turns off. Finally the main battery is drained, it needs to be charged by the external charger.
Point 1 should be the closest point to the alternator output, assuming electricity flow from point 1 to 12, is the wiring of two batteries serial or parallel? I measured the voltage of 12 points while engine being on. 2,3,4,7,8,9,10,11 had the same voltage as the main battery, but point 5 and 6 on the small battery had 14.6V.
Last edited by zuoshulu; Mar 19, 2022 at 11:46 AM.
Would someone have diagram 414-02 for a 2013+ vehicle with the start/stop feature. Trying to help out here, but I only have the electrical diagrams for a 2012.
I found the actual issue which I never wanted to to believe, it was the alternator output wire tip were burned, the rubber cap got a hole and the hex nut lost half body. Luckily, the alternator and the output tip survived, I got 14.3V on every measuring points after replacing the nut.
Congratulations that was a fine bit of troubleshooting and I would have NEVER found it!
So glad you posted back too as I have not seen this problem on an XJ before. How did you think to check that?
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I suspect that maybe the nut got slightly loose, then you have a bad connection which creates lots and lots of heat. Then all that heat damaged the nut and the cover.
I suspect that maybe the nut got slightly loose, then you have a bad connection which creates lots and lots of heat. Then all that heat damaged the nut and the cover.
Well found!
My alternator were replaced twice last year, the first time was done by a professional mechanic who also found out there had been a small oil leak on the right side of my engine in July, roughly leaking about 1 tea cup oil slowly per year base on my oil change interval every 12 month and 7000 miles per year. My oil level was at the 5th bar three month ago, it is still at the 5th bar now.
I actually accept the situation, my other car 2013 Porsche Cayenne leaks more oil. However, the Porsche's alternator was never shorted by leaked engine oil, it is installed in a safer location. Two Jaguar Alternator died last year, the 2nd time was replaced by me in Nov after driving 4000 miles for two long road trips. I decided to take the chance by covering alternator top with a DIY aluminum foil umbellar oil shield and also wrapped it with aluminum foil like roast ham.
No more oil went on my alternator since then, the shield cover seems enough, no need to wrap it again. However, the wire tip rubber and nut seemed to be melt by the heat caused by the extra foil wrapping, I will not take any responsibility if anyone tries to copy my method.
It costs at least $2000 to replace Intake Manifold Gasket and Valve Cover Gasket by any cheaper professional, Jaguar dealer likely charges $6000, new gaskets will fix slow oil leaks, but the repair job will take a whole day. I may figure out how to remove the supercharger on the engine in the future.
Here is a video showing the result of supercharger removal, are there any detail forum discussions on opening up the engine?
My alternator were replaced twice last year, the first time was done by a professional mechanic who also found out there had been a small oil leak on the right side of my engine in July, roughly leaking about 1 tea cup oil slowly per year base on my oil change interval every 12 month and 7000 miles per year. My oil level was at the 5th bar three month ago, it is still at the 5th bar now.
I actually accept the situation, my other car 2013 Porsche Cayenne leaks more oil. However, the Porsche's alternator was never shorted by leaked engine oil, it is installed in a safer location. Two Jaguar Alternator died last year, the 2nd time was replaced by me in Nov after driving 4000 miles for two long road trips. I decided to take the chance by covering alternator top with a DIY aluminum foil umbellar oil shield and also wrapped it with aluminum foil like roast ham.
No more oil went on my alternator since then, the shield cover seems enough, no need to wrap it again. However, the wire tip rubber and nut seemed to be melt by the heat caused by the extra foil wrapping, I will not take any responsibility if anyone tries to copy my method.
It costs at least $2000 to replace Intake Manifold Gasket and Valve Cover Gasket by any cheaper professional, Jaguar dealer likely charges $6000, new gaskets will fix slow oil leaks, but the repair job will take a whole day. I may figure out how to remove the supercharger on the engine in the future.
I decided to take the chance by covering alternator top with a DIY aluminum foil umbellar oil shield and also wrapped it with aluminum foil like roast ham. No more oil went on my alternator since then, the shield cover seems enough, no need to wrap it again. However, the wire tip rubber and nut seemed to be melt by the heat caused by the extra foil wrapping, I will not take any responsibility if anyone tries to copy my method.
As an electrical engineer, I can tell you that electronics hate heat and trapping the heat by wrapping your alternator will most likely kill it from heat instead of oil.
If there's some way to shield it from the oil, like on my E-Type, that doesn't trap the heat, that would be a lot better solution.
As an electrical engineer, I can tell you that electronics hate heat and trapping the heat by wrapping your alternator will most likely kill it from heat instead of oil.
If there's some way to shield it from the oil, like on my E-Type, that doesn't trap the heat, that would be a lot better solution.
2013 Jaguar XJL 3.0L battery charging issues
