Hi all, after going through all the battery drain threads I do feel I need to open my own.

A month ago my 2001 X308 XJR started to say things like "check rear lights" when turning it on. After driving a while, turning it off and on, it was back to normal. Then, starting it sounded like the battery was low. Turns out, that was the problem - when the voltage is low some systems throw an error on startup. Actually had to jump start the car, went straight to the hardware store and got a battery charger.

Turns out, the battery was at 12V (which the charger interpreted as 60%), and soon it would go to 14V or 80%. It never made it to 100%, whatever the charger may mean by that.

Anyway, no problem, back to normal. Well, four weeks later, same problem starts to happen. This evening, it almost didn't start. Definitely sounded like the battery had one last startup in it, and luckily the car turned on. However, once I was home and hooked the charger up again, it immediately showed 14V and 80% charged. What?

Any idea what the symptoms might point to? Is it battery drain or not? Did I charge the battery while driving? Then what caused it to drain so much within 8 hours?

I don't have an amp meter (or whatever you call it), if any of you have any advice what I should get please let me know! Happy to measure around and see what I can find. Maybe it is the horn battery as well, like in many other threads.

 

It points to bad battery, but you can check the drain by hanging multimeter in line at battery terminal an locking the car, it should stabilize at its minimum after few minutes

 

I'd agree with that. When driven the car is charging the battery so it's all good, but the battery isn't holding charge properly so it's nearly flat the next time you go to the car.

BTW I think it's 20-30mins before the car goes fully to sleep to measure battery drains. So an easier way to test if you've not got a meter (provided your boot lock works on the key) is disconnect the battery's neg lead when you park up, if it still seems nearly flat next time you go to start the car then you've proved the battery is going flat on it's own.

 

I started an 08’ XKR instantly with zero volts using this jump pack. I cannot tell you how valuable this piece of equipment is to me.

I like this one a lot as it can desulphate a dead battery and bring it back to life. It can’t fix every dead battery though.

 

It may buy you some time but I highly doubt it gonna fix dead battery
Better spend this money on good AGM battery and you will forget about it for years to come

 

I’m unsure about AGM’s. I’ve seen a lot of red tops that aren’t misused, abused nor mounted other than an acid battery last very long. We have a Noco5 at the shop and it’s surprised me quite a few times reviving questionable batteries. I guess it just depends on the luck of the draw.

 

I have NoCo which works very well, however, the original posting
points to issues which the charger may not overcome.

 

I'll get a multimeter then. I don't think the battery drains so fast that I would see what happens after 8 hours parking. It's been a 3-4 week process before the problems started happening again. Just seemed to accelerate the drain yesterday. So at least with a multimeter I can check if there is any parasitic drain or not.

Other question, what IS a good battery? I have a BOSCH in there but the label seems to be gone or at least I can't see the specs unless I take it out. I know this will start a lot of discussions but bring it on

 

Charger may or may not help, and even if helps it won't restore battery to a new condition so given that price of noco and a new battery is nearly the same i think battery is a risk free choice (assuming it is not drain of course)
I'm a bit out of luck with those chargers, but as you say it must depend on the state of the patient

 

Lots of threads on this subject: start by putting phone on camera and in the glove box. Pull the ignition switch, lock the doors. Open up and check the camera to see if the glove light was on . . . do the trunk, same way. Years ago (a story I have told many times), I put my young son in the trunk of a BMW 2500, told him to knock once the light goes out . . . he didn't knock. Camera in today's cell phones work more efficiently (don' t have to give away a Snickers!).

Lots of other ways . . . to find which circuit is draining the battery

 

Did your son ever make it out?

 

Now a millionaire, owns his own company: spent twenty years in USN as a combat helo pilot. Still eats Snickers!

 

A while ago I wrote a little guide on how to trace parasitic drains on modern cars for my friends in India. Most of the examples I am using are from my 2003 Jaguar. X308 and 1998 Jeep Cherokee.

https://www.team-bhp.com/forum/techn...te-drains.html

Jeroen

 

That's fantastic, thank you!

 

For a true parasitic drain vs. a bad battery

I believe the trunk lid must be closed for a true as the SLCM goes to sleep reading

In the beginning as you pull the ignition key out it makes a linier switch as the ignition rotary switch red item in below pic from pin 4 to 5 , your rotary positions are 1 , 2 , and 3 to the pin 5 , these 1 , 2 and 3 are tricky to read and not confidence building but you are only interested in pin 4 to 5

The pin 5 is a car frame ground that can be disturbed and on M'Lady Penelope my pin 5 was green corroded from fluid intrusion from above ( coffee ? )

The car side of the connector lifts straight up from the mount to pull the connector out to you

This starts the sequence to reach agreements before the SLCM will go to sleep

The steering wheel and seat will move to position to exit the car , if the steering wheel and seat sensors do not see this exiting position the SLCM will not go to sleep

You can turn off these 2 items of agreements by the knob on the steering collum from auto to off and see if your battery holds up and not drained ( overnight ), the pin 4 to 5 still has to work as your SLCM looks at the other agreements like door locks and trunk latches

As a quick test of pin 4 to 5 have the switch in auto and the seats and steering should at least move ( maybe not to full exit , stuck drives or position sensors ) on ignition key removal

The ignition switch from pin 4 to 5 can be freed up with a spray into the key barrel but a dripping mess on your leg

This is a pic of the ignition switch removed from key barrel which you do not have to remove either at this stage

In the worst case if you have to replace this switch the key barrel stays in place and no new key needed

 

Correct. I've seen motorcarman state he latches the boot lock so the car thinks it's shut when he's testing parasitic drains.

 

Aftermarket radio may not go sleep for much longer, mine stays in standby for two days, so need to account for that
i just hanged multimeter outside closed boot locked the car and came back later for results