This forum needs a sticky about 12V battery care

orange4boy · Nov 19, 2009

I see so many people needlessly replacing the 12V battery when all that is needed to keep it healthy is to charge the battery at home with an automatic battery charger twice a week or more.

Chronic undercharging is the #1 killer of 12v lead acid batteries. This usually happens when driving distances are short.

From the Battery University:

Battery malfunction is seldom caused by a factory defect; driving habits are the more common culprits. Heavy accessory power when driving short distance prevents a periodic fully saturated charge that is so important for the longevity of a lead acid battery. According to a leading European manufacturer of car batteries, factory defects amounts to less than 7 percent.

The battery remains a weak link and the breakdowns on 1.95 million vehicles six years or less are as follows:

52% battery
15% flat tire
8% engine
7% wheels
7% fuel injection
6% heating & cooling
6% fuel system

A breakdown due to the battery remains the number one cause.

* Source ADAC 2008 for the year 2007

Acid stratification, a problem with luxury cars

A common cause of battery failure is acid stratification. The electrolyte on a stratified battery concentrates on the bottom, causing the upper half of the cell to be acid poor. This effect is similar to a cup of coffee in which the sugar collects on the bottom when the waitress forgets to bring the stirring spoon. Batteries tend to stratify if kept at low charge (below 80%) and never have the opportunity to receive a full charge. Short distance driving while running windshield wiper and electric heaters contributes to this. Acid stratification reduces the overall performance of the battery.

Figure 1 illustrates a normal battery in which the acid is equally distributed form top to bottom. This battery provides good performance because the correct acid concentration surrounds the plates. Figure 2 shows a stratified battery in which the acid concentration is light on top and heavy on the bottom. A light acid limits plate activation, promotes corrosion and reduces performance. High acid concentration on the bottom, on the other hand, artificially raises the open circuit voltage. The battery appears fully charged but provides a low CCA. High acid concentration also promotes sulfation and decreases the already low conductivity further. If unchecked, such a condition will eventually lead to battery failure.
Click to expand...

mstrkoffee · Nov 19, 2009

I like to charge my Prius' 12V battery by using my car everyday.

hill · Nov 19, 2009

This forum? The main forum? Um, why not be satisfied with the jillions of comments to the battery threads already posted in the care, MAINTENANCE & trouble shooting category. Call me kookie. Just a thought.

orange4boy · Nov 20, 2009

Because sorting through the jillions of comments to the battery threads is a PITA compared to clicking on a sticky that has all the info you need in one thread.

This is one, if not the most common problem with the Prius. Unless you like answering the same questions over and over every time someone has a battery problem it makes sense to organize the info into an easily found place.

But I guess it would belong in the Care and Maintenance forum.

Just trying to help.

This forum needs a sticky about 12V battery care

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This forum needs a sticky about 12V battery care

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