Battery drain; testing the current draw.

[PTR200Jag]

I thought I had better start a new topic as some of the comments re the battery drain problem have spread across a couple of threads now.

Having has the "restricted performance" on the information centre recently I have now charged the battery to maximum and left it a couple of days WITHOUT the connecting to the car terminals.
After charging the battery stood at 13.07 volts, then 12 hours later 13.03 volts.
Twenty fours hours later and this was down to 12.99 and then 12.98 after two days. All good.

I then connected a multimeter to the negative terminal battery post and the other side to the negative terminal from the car. As you can see in the pictures, bit heath robinson but I wanted to make sure there was no danger of the terminals coming together accidentally so I separated them using a rag and a jiffy bag !!








I also disconnected the boot interior lights so that I could test the system without any drain other than the "at rest" systems running.



For this part of the test I DID NOT LOCK / ALARM the car as I wanted to see the quiescent current loss without anything "engaged"
The next part of the test will involve a locked/alarmed car.... just hope its no more than 10 amps to close the locks though otherwise my meter will pop a fuse!

Anyway as you can see, here is the result... in milliamps !!



Interestingly, the figure occasionally fluctuated between 29 and 32 milliamps as if the systems were doing something, self checking perhaps or maybe just changing because they can.

[J44EAG]

The slight ma fluctuation is nothing in the grand scheme of things. The readings you have are very similar to my S-type which has its electrical systems based on the K8. That car has recently had a new battery so I know my set up to be of reasonable and acceptable condition.

Your voltage drops are commensurate with a reasonably good battery. In my opinion, not an issue at all and about normal. If we were to get a really hot weather spike, you could even see those voltages increase due to a change in temperature and SG of the battery electrolyte.

I always try to get battery fundamental issues into peoples heads within the marine industry and indeed within our local Region. It is a simple principle to absorb and remember. Batteries do not last for ever. They can die horribly for a number of reasons or variations as the individual case may be.

Rule 1. Batteries can fail due to lack of voltage stability.
Rule 2. Batteries can maintain voltage but may not have a great storage capacity.
Rule 3. Batteries can die from a variable combination of Rule 1 and Rule 2.

A Jaguar has some of the most voltage greedy and voltage sensitive electrickery I`ve worked on or with. A stable battery platform or chassis is essential for good performance. If I get iffy system performance on my S-type, the first thing I do is drop test the battery. If readings are not to my liking and I cannot get the voltage stability the car needs, then off that battery goes to my store for some further use as an emergency jump starter. A new battery goes into the car and all is well again for a while.

Mike

[oldtimer]

Hi PTR,
Well done, excellent little experiment. We now all know that a target reading with nothing switched on should be around 30 milliamps.

It's got to be an age thing, I can't remember, is it 100 or 1000 milliamps in one amp ?

I'm trying to think how to put 30 milliamps into a perspective that makes sense.
A 5 watt bulb = 0.4 amps. Perhaps somebody can do better than that.

Never the less the load is clearly two fifths of naff all.

Battery voltages are subject to ambient temperature. Once again, cannot remember the details but voltage drops when temperature drops below zero. Initial high readings, referred to as surface charge are usual directly after battery charging.

I shall be very interested to see the readings you get when the vehicle is locked and alarmed.

Just for interest, my 03 YM S type lives in the garage, is never locked or alarmed and is still on it's original Battery. I have a cigar lighter type power socket mounted in the boot and plug in the intelligent battery charger all the time the vehicle is not in use. The Battery is now eleven years old.

I shall keep a watch for part two

Oldtimer

[PTR200Jag]

If you go in at about 0.4 watts then you end up around 30 milliamps, so as you say, Oldtimer, 2/5ths of naff all, or around my way 3/5ths of bu**er all !!

Anyhoo, got to do the lock test tonight when I got in... pulled the cables outside the boot, shut the boot with the interior boot lights still disconnected as I wanted to see if the current changed when they were in circuit, with another test later on.

Tested the battery, first, for voltage, 12.85.

So the meter is now sat on the boot (must get to clean it some time... boot and the meter )

Used the fob and locked it and this is the immediate result....




After 30 seconds or so, this happened



Couple minutes later this;


Unlocked the car, opened the boot and reconnected the boot interior lights...

set locks again and exactly the same result....

Left the meter connected for ten minutes, no change apart from the odd fluctuation as noted in the unlocked test.

So, conclusion is that it uses no more "juice" locked or unlocked. I would have thought that locked it may use more on the basis that the security system is engaged but apparently not.

So why do these models run the batteries down? This minuscule current draw is not the problem. Is it because we dive in and out of the car on a day to day basis without using it, interior lights on etc, dropping windows on hot day without using the car, don't travel far enough to replenish the battery after starting it....

Think the power socket in the boot is the answer but it does mean boot up to use it... where else could it go?

[PTR200Jag]

Rule 1. Batteries can fail due to lack of voltage stability.
Rule 2. Batteries can maintain voltage but may not have a great storage capacity.
Rule 3. Batteries can die from a variable combination of Rule 1 and Rule 2.


Mike

Yes, agree totally... rule 2 is always the one for me, check voltage, apply slight current load and if the voltage drops substantially, around 9-10volts is the usual, the battery is shot

[J44EAG]

I also agree totally with you, particularly as regards usage cycles. Locking and unlocking whilst not starting the car, lights on whilst doors open, short usage (I`m often forced into that situation due to a duff leg and limited endurance with walking), insufficient recharge cycle and headlights, blower, CD player, HRW and cold temperatures all take their toll on battery capacity. You have hit the issue right on the head. I`ve lost count of the times I have a discharged battery after doing a protracted maintenance session over several days.

As we say in the marine game, a light left on, there is your battery gone!

I have begun to use a small solar cell mounted in the rear window of the car. That does help. Only 1.5 amps but useful over a period when the car is not used on the road but frequent boot openings to find tools etc mean there is a drain on services over such a period.

I`ll often advise customers to ditch a battery that regularly fails to recharge successfully and discharges to below about 11.5 volts. In my experience it is rare that battery in such a condition will not let someone down at sea and probably at the most inconvenient of times. I can`t take that risk to my reputation for giving bad advise and suggest that people replace any battery that is even just slightly questionable. The battery may work sufficiently well during the summer but the winter time depressed temperatures soon weed out the duffers. I use a drop tester to prove that point and no one can argue with that.

Thanks for showing those readings. Most useful.

Mike

Mike

[oyster]

Hi.

Very interesting. But I cannot see which setting your multimeter is set at.

Attached is from the battery care manual.

[oldtimer]

Hi PTR,
Most interesting results.

My Battery charger is wall mounted, I plug into the boot socket and shut the boot lid onto supply cable - have been doing so for years

Oldtimer

[J44EAG]

The boot lip rubber is large and soft so there are no crush issues with that. I do the same myself when using an external charger. Just make sure you don`t shut the power supply cable in the lock hasp mechanism!

Mike K

[PTR200Jag]

Hi.

Attached is from the battery care manual.

That's interesting in that an hour elapses before it drops below 30 milliamps or less... I guess if I had left the test running for an hour it may have dropped below the 30ma recorded.

Thanks for the table.

[PTR200Jag]

Hi PTR,
Most interesting results.

My Battery charger is wall mounted, I plug into the boot socket and shut the boot lid onto supply cable - have been doing so for years

Oldtimer

The boot lip rubber is large and soft so there are no crush issues with that. I do the same myself when using an external charger. Just make sure you don`t shut the power supply cable in the lock hasp mechanism!

Mike K

That's good to know, Oldtimer and Mike K, has anyone done an external mount version that you know of?

[MyQuest]

On my last three XKs (1999, 2007, 2013) I've used a CTEK conditioner and never had battery issues with any of them.
I connect the unit's female cable via a fuse to the battery (or power stud on the X150 models), run the QD 'tail' out through the rubber bung in the spare wheel well and plug the CTEK's male connector into it.
Once ready to leave the garage, I separate the QD plug, slip the waterproof cap on the female connector and tuck it up onto the rear bumper lip. (A plastic trim button popped through the bumper makes a convenient hook for its cap retainer tie).
No need to go into the boot/trunk any more..

Mike West

[PTR200Jag]

On my last three XKs (1999, 2007, 2013) I've used a CTEK conditioner and never had battery issues with any of them.
I connect the unit's female cable via a fuse to the battery (or power stud on the X150 models), run the QD 'tail' out through the rubber bung in the spare wheel well and plug the CTEK's male connector into it.
Once ready to leave the garage, I separate the QD plug, slip the waterproof cap on the female connector and tuck it up onto the rear bumper lip. (A plastic trim button popped through the bumper makes a convenient hook for its cap retainer tie).
No need to go into the boot/trunk any more..

Mike West

That seems like a good idea ! thanks

[PTR200Jag]

Well an interesting situation has occurred now... I took the XK off the road at the end of May, primarily to use my soft top S2K through the summer and also to spend some time on the Jag doing maintenance stuff... still got to get started on that though!

Anyway, after 6 weeks left in the garage I thought I had better check the battery ... based on the info on this forum these cars have a mysterious power drain and the fact I never got around to fitting a trickle charger.

I opened the door to pop the boot, no interior lights (LED too), no response from the boot button, obviously. Used the key to manuall gain access to the boot (yes its well lubed!)
3.4 volts !! I pulled the battery out and put it on charge, couple of hours later the charger recorded a possible cell short and the voltage sat at about 11.6v

I left the battery a few hours and then put it back on charge, the cell short appears to have gone ( ) and it is charging normally at the moment... upto 12.5.

The battery was new in November 2014, Yuasa YBX3017, 90 amp hour, with a three year warranty. There are no swellings in the casing, no leakage, and the terminals are "clean" too.

If this battery is good then where did the charge go if the car is only losing 30 milliamps?

Does anyone know if the systems "wake up" periodically to check something or other in their systems??? The car is not locked, no alarm on and no other visible drains such as lights left on.

One thing I will be checking out is whether the boot lights actually go out when the boot is shut... just need a volunteer...

[oldtimer]

Just by way of interest, my old '73 XJ 12 had not been started for about eighteen months but the Battery has been on constant charge. Despite a lot of popping and banging (that's another story but running fine now) started almost immediately. The point being that at least the Battery remained good having the trickle charger on permenantly