Dead!
 

Having a mare. Yesterday. Had to drive 2miles before the rolling door security kicked in. Its happened before always same distance! Often linked with the dash indicator tell tale and the radio not working. The all fine til later in the day the battery is flat and warm!!! and all is dead. Charged last night. This morning absolutely nothing from the key turn - as if the battery was not connected except a dimish dash light for all the red lights but nothing on the second d turn ie no orange management light etc. Dont know where to start. Battery warm concerns me!!

Sent from my SM-J730F using Tapatalk

ooh, warm battery would concern me. This would indicate that is seeing a heavy discharge either through an internal or external short circuit or load. Modern batteries are all sealed but I suspect if this were one of the old fashioned batteries with removable lids then you would either see the electrolyte boiling or smell the gas being given off.

It's possible the battery has failed internally, first thing I would suggest is remove it from the car and leave it stand for a few hours and check the open circuit voltage on it, it'll probably be about 13v. Anything lower and it probably dud - might be worth seeing if it will charge, if it overloads the charger then this is another clue (or take the battery to a garage and get them to test it)

update - just seen that you have charged it, if you've still got nothing then I would still suspect the battery. It might read 13v open circuit but drop to nothing under load. Did you charge on or off the car/disconnected?

Would look at the battery first with a multimeter - at rest a healthy battery will give 12.4 volts -12.8 - if less than 12.4 then the battery maybe knackered - :shrug:

So, the battery is reading very low on a multimeter, so just thought I,d pop a one on of another car - to be honest its probs only half the power needed but would have expected it to power up the ignition properly just to see if I can get a OBD reader on it. That's what I did and no codes stored! typical. This spare battery only gives a click when the key is turned (poss the lesser amperage or is there a big engine to body earth somewhere?) but the central locking doesn't activate and the radio comes on by itself not allowing the volume control work and no visual on the screen - then out of the blue after 2 mins goes dead and the control on and off inactive!! I am guessing that the battery is knackered ( so Ill replace that) but have a hunch there's some electrical issue knackering it. the weird radio thing and central locking and the tell tale indicator dash lights not working as my original post makes me think KBus or similar - which means Im snookered. After fitting a new battery can anyone give me an idea of how to make the next test step?! Any help will be very welcome:shrug:

First thing I would make sure of is that you put a known good battery on, charge the other one up first and then try again.

If there was a short to earth then I think this would be evident by big sparking as you connected up the last terminal, and you don't seem to be getting that.

If the battery that was getting warm has failed internally then this may well be dragging the whole voltage down and upsetting the electronics with the car.

I know you might need long arms, but do you have a voltmeter that you can connect across the battery and observe what happens when you try to start/put lights on etc? If either battery is duff then it could drop down to near zero when you try and start (or even turn the key on)

Thanks I have that under way.

Electronics do not like low power batteries and will throw up all sorts of problems. I used to drive a Jag hearse which used to often stand around a lot. When the battery got low, it would either not start, or light up like a Christmas tree with multiple warning lights. A new (and very expensive) battery cured the problems.:shrug:

if your alternator has a failing bush it will be providing direct current to your battery as opposed to AC and this will knacker your battery. :shrug:

The speedlocking, dash tell tales, and the radio all point at a K-Bus defect, however a load draw enough to flatten a battery in the space of a few minutes needs to be investigated immediately.

I would until the problem is resolved, at the very least disconnect the battery.

So fully charge the battery off the car, and while you are waiting, first check the main battery positive lead along it's entire length, then check to see if the connector on the LSM is free from defect, and see if the cooling fan is free to rotate,

Next if your car has highline audio, make sure the connections are not corroded in the boot.

Finally if the car has electric seats, make sure the wiring isn't snagged anywhere underneath.

Best of luck

Brian :D

I know what you meant, but a failing diode pack in the alternator can lead to AC being fed into the battery, and could also result in the discharge of the battery into the alternator.

DC is the norm ;)

Brian :D