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Sorry if this has been covered previously but getting to the bottom of all your responses is like reading War and Peace. There is a gentleman on YOUTUBE called the Car Wizard. He owns a shop called Omega in Kansas or Nebraska that repairs all makes of cars and exotics. He puts out numerous videos on YOUTUBE including one on 12/3/20 about locating a power (amperage) drain to the battery. In short, he shows how to hook up an amp meter to the battery and check for power draws. He explains what some obvious draws might be like the computer or USB ports, etc. If the amp meter with everything supposedly "off" shows a draw, he goes to the next step. He narrows down and locates the specific source of the draw by pulling individual fuses while watching the amp meter. If the amperage draw goes away by pulling a particular fuse he can narrow the problem down to that circuit. If your car shows no amperage draw that will kill the battery over night, then you can look closer at the battery itself. However, it's hard to believe several batteries would go bad at one time with a good charging system. Look for and watch his video and good luck.
Had the same issue with a 2017 F type S .Final diagnosis was the “Quiescent relay box” Designed to put your car to sleep after 10 minutes. Have not had a problem with low or dead battery since.
Last edited by JohnnyRotten666; 12-04-2020 at 06:02 PM.
Thank you. I talked the dealer into giving me another new battery since this one has been killed about 4 times. Hoping all the advice works, picking the battery up on Wednesday.
Here is an example of someone who does not fully understand the implications of the insurance dongle! Any tracking device that reports on you to a "big brother" is all wrong. Never ever use one of these since it is a super invasion of privacy and it will and does drain the batteries on these cars.
robtroxel,
lol your phone is tracking you everywhere you go (Even when its not connected to the network), every call you make, every website you visit, every search you run, pretty much everything about you and yet I'm sure you keep it on you at all times and in your car where ever you go. So spare me the "someone doesn't fully understand the implications of a tracking device" routine. You happily surrendered yourself and your privacy to our benevolent (At least for now) Big Tech Overlords the minute you bought your iPhone or Galaxy. I'd say letting my insurance company know how many miles I drive is one of the least intrusive things I could do. My problem was that I just didn't figure my $100,000 car would pitch a fit about having it.
I agree that any car should be able to recharge the battery within a short time (20 minutes is NOT short IMHO) - if not that's a **** poor design. I've never checked - however I'd bet our alternators are likely at 100 Amp capacity or greater. A nominal engine start is likely 125 Amps (can be more if cold conditions). This may vary some - but it's in the ball park. If it's cranking for 10 seconds (very generous), then that is a consumption of 1250 Amp-Seconds of energy. Likely at idle, there is not much excess alternator capacity (slow speed equals low alternator output) - but once you get going, my guess is that there are at least 20 Amps of excess generating capacity that goes to re-charging. 1250 A-S divided by 20 A is more like 60 seconds to recharge. This is a far cry less than 20 minutes, so my guess is that we're at or near nominal voltage certainly within 5 minutes if your engine is running at normal revs (not idle). Note I've not checked real data on this car (alternator capacity and/or excess current capability) - I'm simply using reasonable assumptions.
Alright, the Jaguar gods are trying to tell me something.
I am reading this post today because my 2017 was dead as a door nail... no juice... dark and quiet.
Here is my walk of shame:
a) not only did I recently install a KIWI 3 OBD to BlueTooth data server for Track LapTimer use.
b) I also got the dreaded "Low battery - start your f'ing engine" triangle.
c) proceeded to do nothing about it for 5 days...
So, tonight, I quickly got up to speed on getting the key out of the fob, open the door, open the hood/bonnet .. charge some, open the trunk/boot... recharge battery...
That is when the alarm went off.... at 10 PM at night.
Crap... now how does one disable the alarm! (by starting the car with the key in hand?)
You should be able to stop the alarm by simply unlocking the car from the fob. When I had a flat battery the alarm went off as soon as the booster was connected to the underhood terminals. Even through the car wasn't locked at that point the unlock button on the fob did the business.
I'm a little confused - how is what I described different than what's discussed in your link? Note I'm describing NORMAL conditions (not a totally dead battery). I'm talking about the expected time a battery will recharge after sitting not dead (it started the car up so the charge is not THAT bad). I assure you we don't need an hour to run the cars to top off the batteries in NORMAL circumstances. To my data before (that I had not vetted) - I stated that I was confident the alternator was 100A or more. In fact, someone posted 125A to 150A. This simply means recovery is faster. I was non-conservative, however on the starting amps - they are more like 200 to 250 amps. So, we may discharge the battery a little more when cranking, but then it will charge a little faster than I thought - balancing out more or less on the order of magnitude discussion I made. It's 10s of seconds, worse case minutes - not hour(s) to recharge after a start.
@inmanlanier
I think of batteries as being like carboys... they have "capacity" (volume) and "resistance" (throat restriction).
Over time and exposure to high temperatures, engine cranks, and road use, batteries loose capacity (smaller volume), and experience resistance rise (more restrictive neck).
These impact both the parasitic load support (alarm systems, OBD2 port devices, etc) and discharge/recharge rate capability (engine crank, and recharge time).
You are right on typical recharge events. It doesn't usually take more than a few minutes to substantively return the energy from an engine crank, back into the battery.
Engine Crank = 200 Amps x 3 seconds = 600 Amp-sec = 0.16 Amp-hours
Recharge = a few amps of trickle charge current x a few minutes = 0.16 Amp-hours
But what happens when there is a parasitic load in the mix? That can add up to much more than a few Amp-hours of charge removed.
The real question is this: Is the battery strong enough to support future engine crank events?
If the battery and car are cold soaked (it is 20*F / -6*C outside this morning), will it be able to successfully start the engine?
Side Note: a double whammy ... cold makes the battery resistance go up (less cranking amps available) and cold makes the engine crank power go up (more cranking amp demand).
So the Jaguar diagnostic seems to assess the behavior of the battery against the demands of the vehicle, and it gives us a warning that doom is coming.
I casually ignored this warning this week and paid the price.
@inmanlanier
One more commend on the Alternator operation: (Electrical Engineering 101 stuff... please ignore if you are familiar).
Alternators are designed to deliver up to a maximum recharge current, and they are also designed to stop at a maximum voltage level (about 14.2 volts, temperature dependent).
So the battery's internal recharge resistance (which goes up as the battery becomes fully recharged) actually limits the recharge current into the battery during the "constant voltage" phase of recharge.
A battery near full will only accept a small current (less than a few Amps), while a depleted battery may be able to accept the full alternator current.
Note: Load current for head lights and computers is separate from the recharge current ... and the alternator delivers the sum of the two.
Yes, I'm a retired (licensed) ME, with a good bit of experience in controls and power side work as well. This is basic discussion. I have built cars (Cobra replica) and had to live with one of the early examples of a Ford design shortcoming on alternator capacity with my 1984 Turbo GT Mustang (all electrics, but they never upgraded alternator capacity - when the OEM alternator died, none of the rebuilds [reduced output capacity crap] could handle idling with AC on full in South Florida). I was simply trying to share with the folks not to fear the earlier post inferring that each time you start is potentially a significant drain on the battery and how repeated short trips are a risk to continually discharging and recharging your battery. I was trying to factually provide rational data to the contrary. I'm also fully aware of the failure modes of batteries because I on occasion availed myself of one of our EEs who happened to be a well respected battery expert/consultant in the industry.
Bottom line, short trips are fine in these cars with all systems up to snuff is not a risk.
My first response may have been snarkey, so I apologize and offer an edit.
Inman, your theory leaves too much out of the actual equation. If the only draw on the battery was cranking the engine, then yes, the alternator would recharge very quickly with only the exception that a near full battery will not accept much in the way of a charge. As the power balance levels off, the charging comes at a slower rate. Additionally, alternators that are rated at say 120 amps, do not in fact provide all of that directly to the battery. Keep in mind that the power demands of modern cars is significant with heated everything, electric fans, electric controlled suspension, ECU, TCU, USB, etc; often exceeding 3 - 4 KW. A 12 volt system at 3 KW requires a current of 250 amps. Not all systems are drawing at the same time, but there is still much more going on than just cranking the engine.
Last edited by JacksonvilleJag; 12-21-2020 at 07:06 AM.
My first response may have been snarkey, so I apologize and offer an edit.
Inman, your theory leaves too much out of the actual equation. If the only draw on the battery was cranking the engine, then yes, the alternator would recharge very quickly with only the exception that a near full battery will not accept much in the way of a charge. As the power balance levels off, the charging comes at a slower rate. Additionally, alternators that are rated at say 120 amps, do not in fact provide all of that directly to the battery. Keep in mind that the power demands of modern cars is significant with heated everything, electric fans, electric controlled suspension, ECU, TCU, USB, etc; often exceeding 3 - 4 KW. A 12 volt system at 3 KW requires a current of 250 amps. Not all systems are drawing at the same time, but there is still much more going on than just cranking the engine.
Without belaboring the point, you missed some the drift of my statements. I didn't want to make the discussion a 3 paragraph dissertation on all the considerations.
I am fully understanding of what you say. I am in agreement. Of course there are numerous other 'hotel' loads as they would say in the Navy like the multitude of processors, the fuel pumps, the lighting, the HVAC. Some of these loads (like HVAC) can be significant, while others ( sensors, perhaps AC clutch, etc.) are not big hitters. Some of these loads can be continuous (e.g. processors, sensors, fuel injectors, stereo, AC if on and headlights if on), some intermittent (door locks, brake lights and the like). Having retired as a practicing engineer, these are exactly the design considerations that we were tasked with. A perfect example of what we worked with are emergency startup diesels, considering the startup loads they must support, the sequencing of the loading, load levels changing [e.g. high motor startup current vs. lower running current], etc.). But the loads are in the Jag NOT as huge as was being implied by some of these posts, hence why I chimed in.
Normally, there is plenty of alternator capacity to recharge the car in a few minutes at most (not 20 or more). Yes, if you started your car in -10 degrees F at 4:00 AM, had both seat heaters on full, your headlights on high beams, the HVAC on max, your stereo on full blast to overcome the fan noise and you kept rolling your windows up and down to check the snowfall rate - maybe you'd stretch the recharge time to 7 minutes (that's a rhetorical number BTW )! That's the only point I was trying to make.
Well you've certainly made your point as a retired mechanical engineer, so I'll gracefully bow out without stating my retired or current profession or credentials. I'm well versed in debates with engineers. Good day to you sir.
After experiencing a fully depleted battery, I had to use the key, pop the bonnet/hood, precharge the battery, open the boot/trunk, then recharge the battery, turn off the alarm... etc..
The battery was at 5.5 Volts, thanks to my use of a OBD2 plugin for Harrys LapTimer / Track Day Recordings.
Now it is back to "normal" 12.8 Volts, the car shows no warning messages, and it starts / runs and maintains the 12.8V nominal condition.
(I removed the OBD2 device from the port).
So, the Low Battery Voltage alarm seemed to work well in my case... I should have paid attention to it sooner.
I may be in the market for a new battery (mine is the OEM unit from fall 2016, so 4 years old), but I will see how it goes as winter and the temperatures fall to new lows up here in Vermont.
For what it's worth - my dealership replaced my battery at my last oil change (right at 5 years from in service date) for my 2016. A test they ran showed some anomaly in their opinion (I had zero symptoms nor signs). They advised me when I picked up the car that Jaguar had paid for the warranty replacement (I was astonished). I would try that route first.
After experiencing a fully depleted battery, I had to use the key, pop the bonnet/hood, precharge the battery, open the boot/trunk, then recharge the battery, turn off the alarm... etc..
The battery was at 5.5 Volts, thanks to my use of a OBD2 plugin for Harrys LapTimer / Track Day Recordings.
Now it is back to "normal" 12.8 Volts, the car shows no warning messages, and it starts / runs and maintains the 12.8V nominal condition.
(I removed the OBD2 device from the port).
So, the Low Battery Voltage alarm seemed to work well in my case... I should have paid attention to it sooner.
I may be in the market for a new battery (mine is the OEM unit from fall 2016, so 4 years old), but I will see how it goes as winter and the temperatures fall to new lows up here in Vermont.
Final update:
my 2017 F-type is working well after I fully recharged the "depleted" battery...
I did remove the OBD2 dongle to avoid draining the battery, and all is well in Vermont.
No more warnings on the dash, no issues starting the car... I dodged a bullet, or at least until next winter.
Car battery recently died. And had to get it jumped and all seems to be fine now. But I am also tuned so my car has been stock for a bit and now I want to put my tune back on which requires me to put the tuner in my OBD. How exactly can I unplug my battery once I reflash my tune so I don’t run into the draining problem? Or does anyone have any suggestions how to do so?
Car battery recently died. And had to get it jumped and all seems to be fine now. But I am also tuned so my car has been stock for a bit and now I want to put my tune back on which requires me to put the tuner in my OBD. How exactly can I unplug my battery once I reflash my tune so I don’t run into the draining problem? Or does anyone have any suggestions how to do so?
After doing the flash, just disconnect the ground lead to the battery for 15 seconds. It’s easiest to disconnect it where the cable is bolted to the floor of the boot.
12-04-2020, 01:14 PM
)! That's the only point I was trying to make.
