Hi,

I own a car cleaning business where sometimes we do very thorough
detail cleanings of the interiors of the cars.  When we do this, we
often have the car doors open for 4 hours or so.  For 99% of cars,
with good batteries, this is fine.  However, some cars have weak, or
old batteries, and they sometimes die.  Normally, this is not a
problem -- we just jump the battery, but in some cases, when the
battery is really bad, it simply dies and can't be revived.  I know
this is the case because I had a car where this happened to me, and I
had to replace the old battery with a new one.  However, many of my
customers don't know this, and they often think we "killed" their
battery.  So... I'm looking for some articles written about car
batteris and battery life that basically support my case ... that a
car battery usually only dies completely if it is bad to begin with. 
Maybe even explaining why a battery goes bad.  And leaving a light on
or the doors open won't kill a good battery.  The more articles the
better.

---

Request for Question Clarification by sublime1-ga on 02 Oct 2005 17:04 PDT

mikey...

Well, from what I've found, it's true that a single discharge
of the level you're describing won't kill a good battery, but
it won't do it any good, either, and if the battery is weak,
obviously that can push it to the point of no return.

In simple language, the more often a battery is discharged,
the shorter it's life, and the older the battery is, the
more likely it is to be discharged to a damaging degree.

Relevant factors include:

"Never discharge any 12-volt lead acid battery below 10.5
 volts because it can damage the battery."

"Leaving your lights or other accessories on and fully
 discharging a car battery can ruin it due to 'cell reversal',
 especially if it is a sealed, wet Maintenance Free (Ca/Ca)
 type."

Cell reversal is where one or more cells in the battery 
actually change polarity.

Obviously, this is more likely to occur with a weaker battery.

...from a very thorough discussion of battery life expectancy
on William Darden's site:
http://www.uuhome.de/william.darden/carfaq11.htm


Another factor is the quick charge you're giving the battery
to restore it to health. Quick charging does more harm than
good:

"Fast recharging at rates greater than C/4 (amp hour
 capacity/four hours)."

...is a (low on the list) cause of premature battery failure,
per this page on the most common causes, on Darden's site:

Then again, old age is equally low on the list, and the main
cause (repeated 3 times) of premature battery failure is:

"Water Loss! (Car) and Sulfation! (for batteries not used weekly)"

"Sulfation from water loss, undercharging, electrolyte
 stratification, excessive temperatures or prolonged periods
 of non-use account for approximately 85% of the deep cycle
 and starting battery failures that are not used weekly,
 vehicle charging systems based on driving habits (short
 trips with high loads leaving the battery constantly
 undercharged)."

Water loss can occur even in sealed "maintenance-free" batteries,
so refillable batteries are recommended in hot climates.

Another factor influencing water loss is that car engine
under-the-hood temperatures run about 30% higher now than
they did 20 years ago.

Much more on the page:
http://www.uuhome.de/william.darden/carfaq12.htm


Given all this, I would recommend hooking the charger up
*while* you're servicing the car, assuming it can handle
the load of the door lights (and radio?) in addition to
providing some charge to the battery. This would act as
a preventive measure to ensure you have no more failures.


Searches done, via Google:
"a car battery dies"
://www.google.com/search?q=%22a+car+battery+dies%22


Since what I found provides a mixed interpretation of the
effects of your current practices, I won't post it as the
answer you'd obviously prefer to receive, unless you are
happy with the facts even if they don't entirely let you
off the hook.

Let me know what you think...

sublime1-ga

Mike --

There are several options open to you to assist your customers better:
1.  run a battery test when you get the car, using a hydrometer or
other method.  You can let customers know that you're not making money
selling batteries but that you do this as a service to them:
http://www.ibsa.com/www/faqs/tech_talk/maintenance/testing.htm

At a minimum, I'd be checked the battery's in-service date, as 3 years
in the cold northern climates or 5 years in other locations is about
the maximum a lead-acid battery will serve properly.

2.  put the car on a trickle-charger when you're servicing it. 
There's still some danger here because an aged battery under load will
deteriorate quickly due to heat.  And it sounds like you're putting a
moderate load on it by opening all doors.

Best regards,

Omnivorous-GA

I would pull the fuses until I found the one for the door lights.

Sound stuff

However, personally I would disconnect the battery entirely throughout
the cleaning process.

Prior to reconnection clean up the the 'connection' surfaces and apply
petroleum jelly (Vaseline) to both terminals.

Part of the reason why people are bringing cars in to you for a face
lift, is that they have been standing unused for some time.

My guess is that most of the 1% cases got jump started before you saw them.

It might be an idea to talk to a battery replacement shop, they will
give you the low down on spotting problems - one of which is white
powder anywhere round the terminals or, for non sealed batteries, the
cell 'hatches'.

I would just diconnect the battery and include a free terminal
cleaning as an added service.