# What can reduce a car battery life?

In my car the battery life seems to be 2 to 3 years but when i look it up im told it should be and average of 4 years.

What factors can reduce the life of a car battery? some thoughts

• Weather
• Short trips

Not sure what else can be a problem.

• Temperature cycles Jun 20 '18 at 4:35
• Biggest killer of batteries is high ambient temperatures and Vibration. Quality of battery construction determines how long it will perform its job.
– Moab
Jun 20 '18 at 13:29
• @Moab what is considered a high ambient temperature Jun 20 '18 at 21:57
• 100 degrees F or higher. Lead Acid batteries love 80 degrees F. 100F ambient means the battery will see much higher under hood temps which is what shortens their life.
– Moab
Jun 20 '18 at 22:05
• @Moab do you have a sense of how often it needs be over 100F/37c to be a concern to the battery. e.g. is 10 days of the year enough? Or is more regular exposure a concern Jun 20 '18 at 22:23

## 2 Answers

The following can also contribute to a reduced battery life:

1. If an alternator overcharges the battery unit. This problem is usually a faulty voltage regulator
2. Fitting a smaller or lower capacity battery than what a vehicle (starter/alternator) requires.
3. Running a battery flat or passed 10.5V will effectively damage most lead acid batteries.
4. Allowing the battery water to dry up or adding tap water to a battery (instead of distilled).

I'd expect an average car battery to last around 6 years, but this obviously depends on the car, and the usage pattern - if you're doing lots of short journeys and stopping/starting the engine a lot, you'll wear it out quicker than if you do fewer, longer journeys (battery life is determined by the number and depth of charge/discharge cycles, not time)

As @TheLegendaryCopyCoder says, check that you're fitting the right size battery for the car, and that your alternator is working correctly.

As @SolarMike says, temperature also plays a part - batteries will degrade quicker in hot temperatures than if it's cold (but conversely, they will store less energy when cold)

• Do you have a source for storing less energy when cold? What does that in fact mean, accurately speaking? If you charge a battery when warm, freeze it, let it warm up, is the energy gone away somewhere? If so, where? Of course, charging and perhaps discharging a cold battery is inefficient, but I'm not entirely convinced the energy content of a battery would be reduced when cold. Jun 20 '18 at 13:49
• @juhist this is the best freely available article I can find: uk.comsol.com/blogs/… - it states that as the temperature drops, the conductivity of the electrolyte drops, and so the capacity of the battery drops. It's down to the charging/discharging efficiency though, so your example wouldn't see a change, but if you tried to charge it or discharge it when cold, you'd get less charge in or out than if you both charged and discharged at 25degrees C
– Nick C
Jun 20 '18 at 14:17