With a digital voltmeter across the battery terminals, what should be the voltage readings in the following conditions?:

A) Vehicle off (trunk open with smart key),
B) Vehicle on, but not started,
C) Vehicle started.

I am getting 11.94v in A and 14.0v in C. Will try to get the B reading. Battery is still original from September 2008. Vehicle is XKR convertible.

Cheers!

 

Both "A" and "C" voltage readings look quite normal and are in an expected range.

 

Workshop manual says:

• With battery disconnected, voltage should be greater than 12.5 volts
• With ignition off, voltage should be greater than 10 volts
• With engine running, voltage should be greater than 13 volts

So, your readings sound fine.

 

Thanks, richzak. From reading through the maze of battery issues, I'm getting a bit paranoid about the battery it's age doesn't help either. The only issue I have is that when I connect the SDD I get an 'amber' battery icon on the top right hand landing screen, even after I gave it a full charge with my ctek charger.

 

Thanks ngarara, that's reassuring. I will try to check voltage with battery disconnected and report back.

 

Just bear in mind that, if you disconnect the battery, you'll need to reset the windows, the park brake and also the ECM:

• Connect the battery cables and tighten to 5 Nm. Ground cable must be connected last
• Install the battery cover and close the luggage compartment lid.
• Start the engine and allow to idle until the engine reaches normal operating temperature.
• Switch the engine off.
• Restart the engine and allow to idle for approximately two minutes (this will allow the ECM to learn the idle values).
• Apply and hold the brake pedal, select drive and allow the engine to idle for a further two minutes.
• Drive the vehicle for approximately five miles/eight kilometers of varied driving to enable the ECM to complete its learning strategy.
• Reset the audio unit and climate control assembly to your settings.
• Reset the door window motors.

 

Yep, ngarara, followed that sequence (the drive part was the most fun of course ). It is such a pain to remove the battery, though!

 

I damaged myself lifting and manoeuvring an Odyssey AGM battery into my old XJ-S - ended up with a sore shoulder joint for months.

 

Sorry to hear that, ngarara! They're really awkwardly placed!

 

A battery cell is considered fully charged at 2.2V/cell. 6 cells = 13.2VDC

The above voltage would be only the moment you disconnected the fully charged battery from a charger. Then the charge settles down. A battery that is fully charged but NOT on a charger should be around 12.6 VDC.

You get reading below 12V because when the trunk is open a light is drawing power and drawing the battery voltage down. Same for B. I would still prefer to see the voltage under those loads to be slightly over 12VDC, such as 12.1 - 12.3VDC.

With the vehicle running, high 13 to 14V indicates that it is, indeed, charging. One of the quickest way to check if the charging works is to measure the battery voltage with the engine NOT running, then measure it again with the engine running. You should see at least 1 V increase. The charging voltage must always be higher than the battery terminal voltage for it to charge. Like, the pressure on one end of a water pipe must be higher than the other, in order for water to be pushed along.

 

11.94V is way below what it should be.

 

Remember, this is with the battery under load with the engine not running. Jaguar says that a measurement above 10V is normal.

 

https://www.jaguarforums.com/forum/x...-charge-63667/

a chart i posted some time ago

 

If a battery is healthy and fully charged, the load of the courtesy lights and perhaps computers should still not draw a battery down below say 12.5v ... if it does, the battery is near end of life and only exhibiting a high float charge but has no real capacity.

 

Yeah, but an XK draws 10A or more when it's just sitting doing nowt (I've seen it on an ammeter). A lot of that is the infotainment system, apparently.

 

yes and even at 10A, if the vehicle is shutdown and the battery voltage measured in the next few minutes it should not draw down below 12.5v if it is healthy and fully charged

remember the old trick of shedding float charge by turning on all the headlights and the heater blower for a few minutes? a single sealed beam draws right around 4A.

 

Thanks plums. According to this (assuming that the voltages are read with the battery connected), my values are way too low.

 

Reason I put up this post is because I do have a *suspicion* that the battery needs some attention for the following reasons:

1 it is still OEM from Sept 2008, so it's now running at over 5 years;
2 i do notice some odd things such as:
- with IDS/SDD, battery indicator is amber; sometimes IDS/SDD also fails to read all modules on startup, markeing them as 'X';
3 quirks like: rev counter delay following engine start; not always, but sometimes, on startup, the rev counter sticks to '0' then, like half a second later, reads correctly;
4 I use the car infrequently with relatively short (the island is only 17miles long!) drives.

The discharge characteristics of lead acid batteries seem to be quite constant at around 12V, but then drops dramatically; so my worry is that I may end up surprised with no charge in the middle of the night!

I'll try to recharge the battery with the ctek charger (should I disconnect battery?); I will also try to start up IDS/SDD with the ctek charger in place as well to see whether I get a 'green' battery indicator on SDD. Will also get reading B.

Just in case I need to change battery, I have found the Varta Blue Dynamic (CCA = 800A, 95AH) but this seems to be some 15mm higher than the OEM one. Do you think this will have a negative effect on the convertible top stowage?

 

Disconnected battery and checked voltage: 12.3V (answer to B above). Fully charged it should read 13.2V, so I definitely have a partially discharged battery. Hooked up a ctek charger to it to see how it goes. Out of curiosity, below are some other voltages in different situations:

1 12.15V trunk open, battery connected, trunk light on
2 12.24V trunk open, battery connected, trunk light off
3 11.85V trunk open, battery connected, trunk light off, driver door open (key in proximity)
4 11.79V trunk open, battery connected, door closed, ignition on, not started

Looks like my battery is anything between 25% and 50% charged! Let's see what the effect of the trickle charge is!

Checked the battery height. The standard battery is a Varta T8 case; some websites give an XKR battery of an H8 case, which is some 15mm higher than the standard T8. I'm not too comfortable using an H8 as I don't think there is enough clearance between he battery top and the battery cover!

 

I suspect some sites are sufficiently dumb to give to an X100 (old shape) XKR battery spec rather that the X150 (new shape). Have encountered that problem elsewhere on car parts sites. For the X150, you need a BCI Group 49 battery:

L x W x H
381 x 175 x 192mm
15 x 6 7/8 x 7 3/16"

I'm guessing a few mm smaller or larger won't hurt - if smaller, you can use packing pieces.