Engine light to flat battery ??

R

RobJJZ4

Member
Guys,
Had engine light on, running OK, but was low on fuel. Got home, plugged in scanner, turned on ignition, no comms, turned ingnition off, turned on and went to start engine (couldn't remember if it needed to be running) and wouldn't start, flat battery :headbang:

Now on charge. Connected?
 
Anyone?

On charge over night, started fine this morning, still have engine light on, no other warnings. Think I might need a new battery!!
 
NeilP said:
If it was a battery issue, wouldn't the battery light be on instead?
Click to expand...

Previous cars, when running and alternator is good, no light, only get the battery light is the alternator is not putting out the correct voltage.
 
unsure what your problem might be, but over winter i left the car in the garage for about 30 minutes with the lights on and engine off. went back in to turn it on and it wouldn't turn over.

went back the next day, without even charging the battery up and it started first time.

i found it pretty weird, and i still don't know why.
 
Most batteries have a limited ability to self recover from a partial discharge. Something about chemistry I don't understand. Disposable alkaline batteries have this ability to a remarkable degree, it is a significant part of their reputation for long life.

About CEL and flat batteries. Since everything on the car seems managed by a computer, and computers require a steady clean voltage supply, all manner of odd strange problems can crop up with a flat battery. So yes, it can be related. OTOH, there could actually be an engine issue and the low battery sort of stress tested it into presenting itself.

I suspect if you read the codes, then clear them, they will not return. The light may even eventually clear itself after several drive cycles if the problem does not reappear. But you need a healthy battery before making any diagnosis.
 
OK, start fine for the drive home, engine light has gone off..... :?

Will get my multi meter out this morning...... :headbang:
 
Can I ask - of those who have unsealed batteries, how many of you ever check the distilled water level? Simply topping up/ kept topped up seems to give an extra bit of life, though never known a garage to do this on my behalf.

J
 
Jembo said:
Can I ask - of those who have unsealed batteries, how many of you ever check the distilled water level? Simply topping up/ kept topped up seems to give an extra bit of life, though never known a garage to do this on my behalf.

J
Click to expand...

I do. Just top it up to just cover the plates.

I never needed to on #69, but wondering if I should check IMmie's battery as if I leave her for a week and go to start, the ignition comes on and she starts fine but the nav screen cycles down and up again. Once she's had a run, it doesn't happen.
 
Update.... Went to start so I could test the alternator, guess what........ Wouldn't start as flat battery!

Still had the original BMW one, so off the the shop, picked up a new battery, started her up, tested and over 14 volts, so alternator is ok :thumbsup: .

Went for a run, couple of stops, back out today and all seems fine, so fingers crossed, just a battery.

Thought I would check out the cells on the bmw one to see if dry, but it is well and truly sealed :thumbsdown:
 
You might want to use your multimeter as an ammeter and check the current draw on the battery when the ignition is off. If you've got a rogue circuit or a switch gone that is leaving the boot interior lights on or something isn't shutting down and draining the battery you'll end up stranded somewhere.
 
RobJJZ4 said:
OK, 12.5 volts on the battery, next to check when running
Click to expand...

Volts are not the only indicator of whether a battery will turn the engine over and start your car it is the current (Amps) that is more important in this regard.

Compare starting your car to cracking a walnut...

Assume a sledgehammer represents our 12V.

Now in a new healthy battery the available starting current (Amps) could be represented by Arnold Schwarzenegger and so he can swing our hammer and crack the nut (ie the battery has the current to push the voltage out to the starter motor).

In an ageing or partially discharged battery our available starting current would be represented by a small child who is unable to swing the sledgehammer so can't crack the nut (ie not enough current available to push the voltage out fast enough to turn the motor).

Simples.
 
You must log in or register to reply here.
Back
Top Bottom