1996 850 won't jump with a booster pack

Hi, friends,

3 weeks ago my 850 GLE wouldn't start. I found out that battery was
drained (yeah, for no apparent reason). So, I charged it. Took the car
to my mechanic for diagnostic check, nothing wrong was found, they
said just needed to charge the battery. Charged and the car ran fine
for 3 weeks.

This morning car would not start. Lights come on, but engine won't
turn. Battery tests at 11.4 V

Cleaned all contacts on battery and cables. Tried to jump (with a good
booster pack), but car would not start -- sounds like she tries to
turn, just once, but barely, and won't start.

What might be a reason that a fully charged booster pack (jumper)
won't start the car? Where can I look for troubles?

Thanks!

 

Also, to clarify: I checked the fuses, and all are fine.

 

turning ignition switch lights up dashboard lights, and when trying to
jump start they dim, along with headlights

 

12.8v is full stable charge. 12 v is maybe 25% or near dead, 11.4 is
dead. Did mechanic do a load test after it was charged to 13.3v.
Unless the car has a short and if all cables are clean and solid and
alternator charges id say the battery is junk. At 11.4v a booster pack
is in fact the battery since yours was dead. www.batteryuniversity.com
has all the info, charge voltages and how to charge it, If the
mechanic didnt charge it to 13.3, he didnt charge it fully. Dont trust
a charger until you use your volt meter to see what it does, I have
had to adjust my chargers voltage.

 

Dim, or go out?

If they just dim, you may have a bad connection, battery cables
sometimes fail, usually where the wire enters the clamp. You may also
just have a dead (as in worn out) battery, I would take it to an
autoparts store to have it checked out, usually they'll do that for
free. Batteries don't just go flat for no reason, either there's a fault
with your wiring or charging system, or the battery itself has had it.

 

Thanks for the updates!
I'm charging the battery right now, hopefully will be able to start
the car and drive up to get another battery.
Though I wonder, if I'm dealing with something more serious, as I
don't see why a dead battery wouldn't let me jump start the car (fuel
system, starter?)
Will post update later.

 

Usualy one cell can fail , that can make jumping Ng, and bad Cables,
ground, etc.

 

Those jump starter things can only produce a limited amount of current,
they are meant to augment a weak battery, not start a car with a
completely dead one. Even jumper cables directly from the battery in a
running car usually have too much resistance to start a car with a
completely flat battery, you have to wait a few minutes for the battery
to charge from the other car.

Once you have the battery charged, if the car starts you'll want to make
sure the charging system is working and that you don't have a load like
a stuck power antenna, glove box light, cooling fan, etc staying on when
it shouldn't and draining it while parked.

 

well, it was the battery. I charged it overnight. it showed 12.87V.
started the car, drove to a diff shop, to one where I bought the
battery from. they tested the electrical system, found nothing wrong,
and replaced battery for free (was 2 yrs old, still under warranty).
thanks for your help!

 

Make sure every things off before you attach leads or remove leads as they
can cause problems .Are the terminals clean not the connections the
terminals and the connections ?Let it trickle charge for a while then charge
it .