Is it my battery, or is it something else?

[OrangeCar]

Quite a new z4 owner here - about 4 months or so; getting some odd electric things

- About a week ago - I started getting 'Park brake failed', then would take a couple open/door closes before it would start. This happened once or twice.
- Then a few days ago - after parking, airbag failure, brake failure, many many failures, and no longer starts

I went to order a battery - and it arrived today, but the boot will not open now - so I connected the battery to the points under the hood, but the boot still would not open, and the lights are still all dim.

The car is 2014 - and from looking at the log book - the battery has never been changed (33k miles) - so i'd have guessed battery certainly needs replacing, but really thrown why boot will not open / lights are not back on full, once I connect the new battery to the points under the bonnet

Should I leave the new battery connected for longer under the bonnet? Will this just drain the new battery?
Should I get one of those portable car battery chargers, and leave it for a few hours?
Is there something else I am missing? Aware it could be the alternator too - but not sure why this would stop the boot / lights coming on full once I wire new battery to bonnet points

Any suggestions welcome - currently have a 1 tonne paperweight in my garage.

 

[Ed.Straker]

My guess is that the old battery is completely flat and now may be useless
Best thing would be to attempt to charge it via the engine bay charging point with a CTEK type recovery charger over a 24 hour period
Then attach a freshly charged battery to the engine bay point
With some luck you’ll then have enough energy in the system to allow the boot to unlock
Leaving the battery in that state may have rendered the electronic parking brake fried which will need a specialist to recover
Until you can change the battery in the back you’ll not know

 

[OrangeCar]

My guess is that the old battery is completely flat and now may be useless
Best thing would be to attempt to charge it via the engine bay charging point with a CTEK type recovery charger over a 24 hour period
Then attach a freshly charged battery to the engine bay point
With some luck you’ll then have enough energy in the system to allow the boot to unlock
Leaving the battery in that state may have rendered the electronic parking brake fried which will need a specialist to recover
Until you can change the battery in the back you’ll not know

Got it - so I guess I need both a charger, and the new battery? *starts getting ready to head to store*.

I am getting 12v read from the points - in the engine bay; hopefully not completely fried the parking brake

 

[OrangeCar]

Got a the charger, and will plug it in tomorrow / leave for the day

I am still confused - why when connected to a new battery via engine bay, all the lights were still dim / still not opened the boot- any ideas? I'd have expected it to have pulled some power in. I also had no luck trying to jump start earlier.

 

[javis20]

I had a Passat that exhibited the same problems. Even with a jumpers and battery chargers, it failed to start. I fussed for days until I removed the battery and installed a new battery. Then it started immediately. Your problem is going to be getting that trunk open...

You may want to measure the battery voltage with charger connected. If it's less than 12.6V, you got a problem. Possibly a dead cell. May have to get a really powerful charger to bring the voltage up.

 

[Ole gits rule]

You will also need to register the battery to the car when installed I believe

 

[Zed Baron]

Many moons ago I had the battery disconnected and then accidentally shut the boot! I connected jump leads under the bonnet to one of my other cars, wasn't enough power to start the car or anything, but enough power to hit the central locking button twice and open the boot.

 

[clarker63]

Some code readers can open the boot (assuming there's enough juice I guess, which may be your issue). there's also a hack on the junction box too to open it if you google it, I believe.

Alternatively, have you got a charger (such as a CTEK) that can recharge dead batteries? leave that on for a day or so.

Good luck!

 

[dumaurier7]

Got a the charger, and will plug it in tomorrow / leave for the day

I am still confused - why when connected to a new battery via engine bay, all the lights were still dim / still not opened the boot- any ideas? I'd have expected it to have pulled some power in. I also had no luck trying to jump start earlier.

Because the dead battery is pulling all the juice! I opened my locked boot a couple times by setting my charger on high (10A) and connecting it at the points under the hood, worked every time.

 

[OrangeCar]

Quick update -

- Left it charging for a day - was drawing 10A for almost 10 hours - and would reduce to drawing 1 amp or so, i'd take off charger, and within miliseconds it would be reading 8v (from engine port points).
- Ended up following the instructions on https://z4-forum.com/forum/viewtopic.php?t=130299 - pulling the fuse box, to override roof codes with a new battery connected directly to the fuse box (slight tweak on the how to)
- Once trunk open - was clear the old battery had an issue - the red terminal part (plastic and what not), was melted - even had melted the nut and bolt together. Took a lot of both WD40 and elbow grease to release [ see picture below ]
- Fitted new battery in trunk - with an amount of insulation tape (until I get hold of a new positive terminal part)
- Lights were all back to full - cleared all errors codes, and fortunately - brake system all good.

In summary - old battery died such that it was shorting when being charged, and only discharging 8v. It is not clear if trying to charge it melted the terminal, or if this was part of the failure. The fuse box 'workaround' is a hero.

 

[deltasierra]

The melting we see on the red terminal is probably due to a loose connection that has heated up, rather than a short circuit.

 

[matsmith749]

You need to look into all the ground etc & consider replacing the primary +12v line as well as the connectors.

I suspect new battery will fix your issues for a few days only.

Something caused this - you need to find out what, and fix it.