Hello Jagfolk,

So I had my 2001 X-type sitting in the basement of my apartment for 20 days since my last drive with it (didn't realise it was so long ago). Anyway I had my road assist come out and have a look at it (this is the 3rd time we have met, same issues last time too) and this is a new battery less than 2 months old with a voltage today of 1.07.

So he hooks it up to another battery and it starts, great. After a few tests he says that the alternator must be faulty because the car is overcharging. At engine idle the car is at 13-14V then when I rev the engine to 2000 it becomes around 15V. This is then repeated with idle of 15.08V and loaded (highbeams & revs) of 15.13V.

The same test a few months ago before I got the battery changed showed idle of 15.21V and loaded at 15.1V, but we both overlooked the high voltage figure.

So two questions:

1- Does the X-type charge normally at 15V, either initially or constantly?
2- With a drain test of 0.04A, 0.06A & 0.01A over 4 months how does my battery keep getting to a severely discharged state?

 

I think if you check JTIS you may find it charges at an elevated voltage for a while until it drops it to a lower one. It aids battery health. Fully charge your battery (which may not recover, but it might) or get yet another new one then repeat car voltage checks after driving for (say) 30 mins.

 

You might look into a voltage stabilizer. They are supposed to extend your battery life. They act kind of as a back-up reservoir to your battery that charges along with your battery then is there when the car needs the extra juice to keep things running smoothly. I'm not sure it would fix your problem here, but it may help you out. I am not sure what would be causing your battery to drain so fast in 20 days...

 

Total garbage. The car is properly designed as-is.

 

Lancer, are you using an RMS meter or a standard (cheapy) meter? I ask this as the values that we can expect to see are based on a higher quality meter that reads out in RMS DC. THe cheapy multimeters can read out in peak DC. How this can affect what you are seeing is a higher quality meter will read 13.7 VDC, where the cheapy meter may read out at 14.4 VDC on the same car, at the same moment. That alone can account for some of the higher reading.

Also keep in mind that right after starting the car, the ECU artificially raises the voltage up to around 15 VDC to put back what energy was used for starting the car. The higher voltage can last for up to a few minutes.

As for what can kill a battery in a fairly short period of time, the list is too numerous to post here. In short, if you have added anything to the car (aftermarket amplifiers, GPS unit, car alarm, etc), these can continue to pull power, even with the car off. The car already has a small draw (normally around 40 milliamps (0.040 amps) from the computers that are already in there. So, even with a everything else being perfect, the battery will get depleted by the factory stuff. Keeping in mind that most batteries are rated for around 80 amp-hours of life, letting the car sit for 20 days will have you discharging about 25 amp-hours from the battery. So, you have already removed over a quarter of the power from the battery. This can significantly affect how well the car starts. Should it pull the voltage down to 1.07 VDC, by no means. So, there is something else going on. For you to reach 1.07 VDC, you had to reverse 2-3 cells inside of the battery. Normally this is a death blow to a battery, especially if the discharge happens quickly.

I would say to remove the extra stuff out of the car (including any cell phone chargers or anything else that plugs into the cigarette lighter) and see what happens. If you are going to take a measurement of the voltage system, connect it up across the battery with the engine off. You should see 12.6 VDC (regardless of the meter type). As you start the car, the voltage will drop (normally to around 11.5 VDC) and then as the motor catches, it will shoot up to around 15 VDC. Note this voltage. After a few minutes of idling, it should have dropped to around 13.7 VDC (assuming higher quality meter) or 14.4 VDC (with a lower quality meter). As a general rule, the alternator will drop by about 1.5 VDC from the peak voltage right after starting to its normal point.

 

Thanks for your replies. As far as the meter goes, I have no idea it's not mine, just the road assist's one. I assume it would be fairly good quality considering that's their job.

After start up is exactly when we tested the voltage, so the ECU must have been putting out the 15V like it normally should. In that case my mind is at rest and I can go around driving my car again.

As for the power drain I've done too many electrical modifications to the car although everything is powered once the accessories come on so not sure why(if) it should still be drawing power when the car is off. In any case it would be too much hassle to pull the trim apart and disconnect them for a test so I'll go out and by a charger to hook up every week or so.

Best place to be for a Jag, go the forums

 

Lancer, I mention things like the aftermarket amps as while they are only powered on when the radio is turned on, they have a circuit that remains energized all the time waiting on the trigger signal from the radio. So, they will pull an additional 20 mA or so from each amp. So, if you have say 2 amps in the car, that would be an additional 40 mA on top of the 40 mA from the car itself. So, now you are pulling 80 mA 24 hours a day from the battery. This will lead to the battery draining that much faster. Now you add a aftermarket radio, that can add even more. You have a cell phone charger, that will add in more too (even though the phone may not be plugged in). It isn't any one thing that is killing you right now. It is the combination of a lot of things most likely.

 

Thermo thanks for the clarification very helpful!

As far as I remember I have an aftermarket head deck, reverse camera, front and rear video recorders and external courtesy lights. Anyone of those could be pulling a little bit of extra power although I made sure they're only connected to the accessories (apart from the head deck which needs both always power and accessories). Perhaps that's the culprit then?

In any case everything thing is hardwired to the car which makes it too hard to disconnect/reconnect often and I managed to get a replacement battery since the last one wouldn't charge at all after putting it on the charger for 24 hours.

Just went on a road trip and everything went very well, so I might need to keep the car on a charger if I'm leaving it for a while.

Thanks