Voltage output spec. ?
 

Today i decided to plug in my little portable volt meter which plugs into the cigarette lighter. Interesting that the lighter socket goes hot as soon as you get into the car. Well it read 12.5 Volts prior to start up. After starting it went up to 13.6 volts for about the 1st 2-3 miles of my drive. After that it settled down to 13.1 volts and stayed there for the entire drive. Now granted I am reading voltage from a point in the circuit that may take some losses but I was just curious if anyone knows what the voltage output should be during normal operation. When I got the car last Friday I put the 10Amp charger on it for a few hours and then put the 2 amp smart charger on it and it went to float (green) in about 10 minutes. I have not found anywhere in the OM what the correct voltage is so I was wondering if anyone has that info. Next time out I'll take a reading from the back where the + stud is located.

In my 2009 XKR, in the glove box, there is a 12v outlet that turns on/goes hot when starting the car and off when turning off the ignition. I assume the cigarette lighter is the same?

I have my dash cam plugged into the 12v outlet in the glove box which is perfect for the dash cam. Starts recording once starting the car and stops when turning the ignition off.

Not sure about normal voltage readings when being driven.

Are you going to install a battery smart maintainer to keep the battery fresh?

I have a 2 amp smart charger hooked up when the car is not in use.

I am still doing lots of voltage checking on my XKR since the battery died last week. I charged the battery back to normal and been checking the voltages every few hours after the charge was completed Monday.

According to most experts a fully charged battery that is at rest is 12.7 volts.

When you start the car and the alternator begins to charge, the voltage should go well over 13V and stay there as long as the engine is running and the alternator is charging. Depending on the voltage regulator settings, it may settle at that charging voltage or it may lower/raise depending on the charging algorithm. Your values with the engine running appear fine.

My battery when fully charged Monday was 12.73 Volts, after a few hours "rest" following the removal of the charger.

Tuesday, a day later, voltage was at 12.63, which indicates that that battery had lost about 10 percent charge in 24 hours with just normal discharge load of about 0.04 amps.

Wednesday (today) the battery was down to 12.51 V, that now indicates a full 20 percent discharge since Monday.

Such quick discharge indicates either that I have a weak battery or, something is drawing current in the car. I checked the draw with everything shut down, doors/hatch closed and it is only 40 milliamp with would only justify a 1 percent discharge per 24 hours.

One thing that may be a variable; all along the above reads I left my trickle charger connected to the battery terminals but, not plugged-in to charge. I checked this morning and the trickle charger itself is using 0.031 amps (31 mA) when not plugged in to charge. So, that makes the total discharge 40 + 31 = 71 mA. But, 71 ma still only comes to 1.7 A per day discharge, which is close to 2 percent battery capacity. Yet, I appeared to be loosing about 10 percent/day.

So, as one more check I recharged the battery to 100 percent, disconnected the trickle charger and starting the drain checks all over again.

For your info here is a rough guide on how to tell how far your battery is drawn down, just from the voltage reads: all reads are for a battery with no load or no discharge. With normal 40 mA discharge from a connected battery the reads below would be slightly lower.

100 percent - 12.7V
90 - 12.62
80 - 12.50
70 - 12.37
60 - 12.25
50 - 12.10
40 - 11.96
30 - 11.81
20 - 11.66
10 - 11.51

The standard quiescent draw of an XK is supposed to be less than 30mA. TPMS makes the shutdown period longer, which can account for some increased drain. A tracker system will increase drain, particularly if its internal battery is getting old.

Your battery certainly seems to be losing charge pretty fast, if the voltage readings are a true indicator of charge. It's weird; we both have the same model, more or less, yet mine will sit happily for a week and then start & run fine. And mine has a (non-Jag) tracker system fitted, and a non-AGM battery.

The manual mentions "If intermittent wake-ups are suspected, monitor battery current continuously" - you may have to get a recording ammeter to see if something periodically comes to life & draws extra juice.

Are you locking the car when you exit? Doing so will put it to sleep right away, otherwise everything stays in some kind of stand-by mode for a half hour or so. I've gotten into the habit since reading about it on this forum.

Yes, lock the car always immediately on exit.

My XJL, that gets low battery warning every time I open the door to load the car, would sit 3 weeks at the airport and still start. I just checked my wife's XF that has been sitting there for a couple of weeks and that one had a voltage level of 12.31.

Yes, it appears that either my battery is weak or something "wakes up" after being shut down. Damm, I just HATE some of these "modern" electronics. Why can't everything shut down when I intend to shut things down?

Yes, if this keeps happening I will have to get a current monitor/recorder. What kind of tracker system does your car have?

As I familiarize myself with the car I see how there are various ways in which there is current draw. Even if you lock it up at night when you go to the car the next day the draw process starts. Consider this as you touch the keyless entry power starts to be consumed. My bet is this is not trivial as just look at the draw needed to unfold the mirrors and then crack the window as you open the door. The 2 lighter socket energize as well as the seat functions. There are probably others that we don't see or hear. Doesn't the start button start to glow and flash. All this before you even push the start button. Once you do that you get the major draw as everything else goes in to power up mode. It makes me wonder why Jaguar left out a volt gauge. Thanks to all on this site I had been for warned about making sure the battery was topped up and I use a smart charger at night.

Was that completely disconnected on the bench? That would seem low for just a few hours rest. Perhaps it wasn't fully charged yet.

Someone mentioned you have an AGM battery? They like a more agressive charge. Your chargers may have a program for those. The CTEC is supposed to have a AGM setting.

On a 2001 Denso alternator, the charging voltage on mine is at 14.2 vdc when idling measured at the underhood fusebox stud. That is the farthest point from the alternator/battery on that car.

AGM's like up to 14.8 vdc when replenishing the starter drain.

ps. from my paper records, after a full two day trickle charge, the battery read 13.26 volts at disconnection and took two days to drop to 12.87 vdc without a load of any kind. battery label says June 2005.

I wrote "a few hours" simply because I did not exactly record when the voltage finally dropped to 12.73 after a full charge. Today, I am checking, however; when disconnected the charger at 2:15PM, my Fluke 87 read 13.39 V. Right now, at 9:43PM it reads 13:20 V.

I have a Jaguar labeled battery, made in Germany 36/11 and installed on 5/2012. So, it has been in use for two years.

The voltage reads I quote are with the battery installed normally in the car, with doors/hatch locked. I did loose about 20 percent charge in 2 days. That was shown by the battery read (12.51v) as well as the fact that it took about 5 hours of charge at 4 Amps (20 A/hr) to recharge this 100 A/h battery completely. If this quick discharge pattern repeats, I'll get an AGM battery. Still, this 20 percent discharge over 2 days does not explain the catastrophic discharge to 5.2 V in 3 days, last week.

It's a UK/Europe system called TRACKER (bonus points for good marketing!):

TRACKER

It has its own battery and sensors, so it can tell if the car is being jacked up or moved while the ignition is off. Had it on my previous car as well - and triggered it a couple of times when the car was being recovered after a breakdown, so I know it works.

How certain are we that the outlet in the glove box goes off and on with the engine? I have my iphone cable plugged into it (no phone connected) and when I opened the glove box to grab the OM I saw it had an indicator LED lit, so I connected my phone and it started charging. Having read enough about battery life in Jaguars, that really got my attention.

This is an old thread but to answer your question, my cigar lighter and glove box outlets get powered up when a car door is opened. The engine does not need to be running.

Thanks! I know it is an old thread, but also know better than to start a new one with this question. “See that box that says search? Use it!” :)

That's called Convenience Mode. :icon_rtfm:

https://cimg6.ibsrv.net/gimg/www.jag...867745088d.jpg

You can learn a lot by reading the Owner's Handbook.

Sigh... the previous owner misplaced mine... so I am running blind.

I live by the Engineer's Credo: When all else fails, RTM

Yes, convenience mode. I had forgotten the term. Time to re-read the manual I guess.

Scott in PA, you can download the manual at
https://www.jaguar.co.uk/owners/hand...k-library.html

Thanks, and as a new owner I did read the manual - this is what I found on the topic, didn't think "Locks" would provide useful details. :)

"An electrical accessory socket is located inside the glove compartment. This 12 volt socket should only be used for the temporary connection of electrical items, such as a vacuum cleaner or cool box. CAUTIONS Only Jaguar approved accessories should be plugged into the power sockets. Using any other equipment may damage the vehicle's electrical system. If you are in any doubt contact a Jaguar Dealer/ Authorised Repairer. The engine should be running when using accessories for long periods. Failure to do so can discharge the battery."

What that means is that the cigarette lighter and power socket in the glove box are live as soon as you open the door, even though the engine isn't running. Leaving an accessory plugged in without the engine running can drain the battery because the alternator doesn't work to charge the battery when the engine isn't running.

Simply put, those electrical circuits are switched. That means they have no power when the ignition switch is off, and have power when the ignition is on regardless of whether the engine is running.