How long until battery's dead??

I have an anti-theft device on my '01 PT Cruiser. You have to turn the
headlights on to start the car. Which is fine until you forget to turn
them off. Today I forgot and I shut off the ignition. About 40 minutes
later I noticed they were still on. I tried to start the car, it
cranked about three "whirls" then "click, click, click..........."
I charged the battery and then went and had it tested. It tested as
being fully charged and in good shape.
Seems to me that the lights should have not killed the battery in this
short of a period of time.
It's the original battery, I guess I should replace it before the
weather turns cold.
How long should a fully charged battery be able to keep the headlights
on and still have enough current left to start the engine??

 

The original battery in our '96 Stratus lasted at least 5 years, IIRC.

How many Watts are the headlight bulbs on the PT Cruiser? Let's say 60W
each; that's 10A for the headlights. Plus another 2 or 3 Amps for the
rear lights, perhaps. Even if we say 15A, I would expect the battery to
keep them running for 2 to 3 hours -- but whether there would still be
enough left to start the engine at that time is another story.

Perce

 

I have had a brand-new high-capacity battery keep headlights on
in my wife's car for 8 hours then still start the car afterwards.

I think your battery is probably still good but is nearing the end of it's
lifespan. You may have some corrosion on the terminals - take apart
the terminals and give them a good brush with a battery post brush,
or better yet remove the battery, clean the top off with a hose, give the
terminals and clamps a good brush, put it back together and spray on
the battery corrosion inhibitor.

A deep discharge on a car battery like leaving the lights on once or twice
generally won't hurt it if you charge it up again right away. Repeated
deep discharges will shorten it's life

Ted.

 

Interesting how different this is with lithium ion and other 'solid-state'
batteries for gadgets.

BTW, it's "its", not "it's" in your sentence...

DAS

For direct contact replace nospam with schmetterling

 

You can buy marine lead acid wet cells that are the same form factor as car
batteries that will take repeated deep discharges with no problem, people
use
them for trolling motors, etc. They are not good for starting cars,
however.

From what I understand this problem isn't specific to lead acid batteries in
general, it is specific to car batteries because their plates have been
modified to
optimize the ability of the battery to dump immense amounts of current into
the starter for a short period of time. There is some kind of mechanical or
chemical tradeoff that is made there which limits the ability of the battery
to
be drained down past 20% of its capacity on a repeated basis.

The only problem that is specific to lead acid batteries, and affects all of
them from Optimas to UPS gel-cells, is that if they are stored discharged
for any length of time with an electrolyte in them, the plates will sulphate
and the battery will be destroyed.

Sorry about that, it is one of my blind spots in writing.

Sigh.

Ted

 

That's interesting. When I last researched batteries about 10 years ago
or more, I found that of all of them, the lead acid batteries were most
likely to come back from deep, deep discharge. Now this was in general,
not for car batteries but for the lead acid batteries I would buy in an
electronics warehouse.

 

Right. Also note, that a discharged car battery is much more likely to
freeze and the expanding solution will distort the plates and that alone
will kill the poor thing.

Richard.

 

and i would bet you never serrviced the battery and it has corrision all
over the top of it, to boot, but it should have lasted longer!!!