Battery keeps going flat

[Dallas]

Since I bought the Trophy blue ZT back in the summer, it has always suffered a flat battery. I first thought the battery must be past its sell by date, and a new battery would indeed be needed. Once the battery was charged it would again go flat after 5 days, this was during the summer months.

The problem seems more likely that something is draining the battery, I have changed the battery 3 times with a good replacement. I have 3 good spare batteries in the shed, and each one is going flat once connected to the Trophy blue ZT.

I dont have the CD/DVD Satnav system, but I do have the Harmon Kardon setup, could it be the amp/sub thats in the boot causing the drain, or some relay somewhere?

The plenum chamber is bone dry, the car is a 2.5 V6 petrol manual if that helps.

Cheers guys.

[COLVERT]

Could you tell us please what the voltage reading is across the battery terminals with the engine running ??

Also how do you know all these batteries you mention are all fully charged ???

How do you check them ??

If they haven't been touched for at least 24 hours the voltage reading on each of them must be at least 12.6 volts.

Even this is not a perfect test. With modern sealed batteries the only way to test them is with a garage Drop Tester.

Good luck.

[Dallas]

Hi John, You know that Carpoint Jumpstarter that I purchased from Amazon, I'm happy to confirm that it has just started my 2.5 petrol engine with ease.

I have just performed those tests that you ask.

Q: Could you tell us please what the voltage reading is across the battery terminals with the engine running ??
A: Running 14.4. Not running is 11.6.

Q: Also how do you know all these batteries you mention are all fully charged ???
A: The 3 spare batteries I keep charged, only select the long slow trickle charge option, one of them is only 10 month old.

Q: How do you check them ??
A: Battery charger voltage reading, and a multimeter.

Q: If they haven't been touched for at least 24 hours the voltage reading on each of them must be at least 12.6 volts.
A: Correct... the 3 spare battery readings are as follows... 12.6, 12.6 & 12.7.

In all the years I have been driving and experience this problem, a new or replacement battery has solved the problem. But! this time the replacement batteries are also going flat, surely this must mean an electrical current drain problem/fault.

[COLVERT]

Wow. that was a fast reply.---

All then seems OK, except for the battery on the car. That is terrible.--

If the battery is mechanically sound then you have a job on.

Find out where that current is leaking to.

To flatten a fully charged battery in just a few days the leak should be reasonably easy to find. Maybe some component is actually feeling warm to the touch.

Otherwise it usually boils down to disconnecting various things, with an amp meter attached in line, to find which item is causing the problem.

Fiddly job which can drive you mad,---

[BoroRover]

Originally Posted by COLVERT

Wow. that was a fast reply.---

All then seems OK, except for the battery on the car. That is terrible.--

If the battery is mechanically sound then you have a job on.

Find out where that current is leaking to.

To flatten a fully charged battery in just a few days the leak should be reasonably easy to find. Maybe some component is actually feeling warm to the touch.

Otherwise it usually boils down to disconnecting various things, with an amp meter attached in line, to find which item is causing the problem.

Fiddly job which can drive you mad,---

Can be a fiddly job. The culprit on a previous Rover Sterling was the fuse below the electric drivers seat, needed an experienced auto electrician to find that one.

[Dallas]

Originally Posted by COLVERT

Wow. that was a fast reply.---

All then seems OK, except for the battery on the car. That is terrible.--

If the battery is mechanically sound then you have a job on.

Find out where that current is leaking to.

To flatten a fully charged battery in just a few days the leak should be reasonably easy to find. Maybe some component is actually feeling warm to the touch.

Otherwise it usually boils down to disconnecting various things, with an amp meter attached in line, to find which item is causing the problem.

Fiddly job which can drive you mad,---

Lol I've had my bonnet up all afternoon, been meaning to do some tests but not had anytime until now. I only know the basics, so I doubt I'm going to find the problem/cause. I've never had an electrical battery drain fault before, so where do I start.

What components are under the bonnet that can malfunction and cause power drain?
I was thinking maybe the Harmon Kardon amp, those amps can drain batteries if the components are breaking down due to age. The silly thing is... I would rather the car NOT have the HK system, I prefer it without.

Where would I find the amp, is it easy to unplug the power cable?

Can anyone who has the HK system confirm its trouble free, have they ever had battery drain issues?

Thanks all.

[Walter]

My saloon has HK system, never had problems, amp is in boot drivers side behind lining

[Blackrose]

Wes, first of all rig up an in line digital ammeter. This should show the current drain. I suppose the easiest way would be to start pulling fuses till it disappears, at least then you will know which circuit it's on. Make sure all your interior lights are going off including the boot light.

Blackrose

[COLVERT]

One of the possible leaks is a faulty diode in the end of the alternator.

Instead of only current in one direction it is possible, but rare, for very low current to run the opposite way.

That amp in the boot though. I think I've read on here that quite often is a problem. Maybe someone could throw a bit more light on this.--

[Dallas]

Originally Posted by Blackrose

Wes, first of all rig up an in line digital ammeter. This should show the current drain. I suppose the easiest way would be to start pulling fuses till it disappears, at least then you will know which circuit it's on. Make sure all your interior lights are going off including the boot light.

Blackrose

How do I do that? I have an idea, but can you just jog my memory a wee bit. Thanks buddy.

Originally Posted by COLVERT

One of the possible leaks is a faulty diode in the end of the alternator.

Instead of only current in one direction it is possible, but rare, for very low current to run the opposite way.

That amp in the boot though. I think I've read on here that quite often is a problem. Maybe someone could throw a bit more light on this.--

Thanks John, I need as much help as possible, any advice to make the job easier and quicker, much appreciated. Its too blooming cold messing around on the drive in this weather. I suppose the first thing I should do is pull the power plug/loom from the amp, then put another fresh battery on and leave car stood for one week and see if battery still goes flat.