Your car battery dies all the time and you don't know why

Batteries and Alternators

Vince L.    Advice compiled from various Calgary driving schools | October 8, 2014
So your battery dies. You need a boost. Luckily we live in Calgary and some nice person decided to help you in the name of Christmas spirit. Now your car has started and your saviour is gone what do you do? Well you need to let your battery charge up again, so you decide to take the long way home and that should be the best way to charge up your dead battery, right? Wrong!

The best way to charge a dead battery is not by driving it but by starting it and letting it sit there and idle. Once your car starts your engine will be running and thus spinning the alternator. The alternator is the device in your car that will convert mechanical energy into electricity. Even if your battery is completely dead, as long as you don't turn off the engine the car will continue to run. Normally, alternators in cars will produce 14.2 to 14.5 volts. While the car is driving, most of these volts will go to operating the many features requied while driving the vehicle - such as signal lights, radio, heat, and fans. The rest of the volts will be reserved for charging your vehicles battery.

So why is idling the best way to charge your car since it charges while your driving as well? This is because the energy needs of a vehicle while it is driving may vary. The heat, the lights, the radio etc will all need some power to run these simple features. All of this combined can often use more volts than you think - leaving less for the battery. If your battery is having issues such as a dead cell and is already providing a lower output of energy your car will not charge efficiently while you are driving. The best plan is to start your engine from the boost, then turn everything off that may need electricity to ensure it is not draining your battery and the energy produced by the alternator. When you leave your vehicle idling and not driving, this will maximize the voltage that your battery will get and thus should charge a completely dead battery to over 70 percent in under an hour.

Can I just get a bigger battery?

Since the battery is capable of producing around 14 volts why then does only 2 volts go to charging the battery? Can I get a bigger and better alternator or even battery to ensure that my car never dies?

To answer this question we must first learn about the special relationship between the battery and the alternator. Larger batteries with more capacity are available, however you must first check to ensure that the battery will fit inside the battery compartment under the hood. However alternators must be manufactured to specifically produce around 14 volts.

Why? Any voltage that is under 13 volts will take a very long time to charge the car battery take for example battery tenders that have a slow trickle charge can take weeks to charge a car battery to full. Voltage that is higher than 14 volts will prematurely dry out the battery as it boils the electrolytes out of the battery. At this point you will be able to visibly see corrosion growing out of the battery terminals. This can be dangerous as it increases the risk of explosion. Take care to always check your battery for these signs.

The most common problem if your car battery always dies is that the battery capacity is very low due to a dead cell within the battery. Check the cold crank capability of your battery and you will see how much capacity is left in the battery. If this measure is low then it means it's time for a new battery. Most establishments that service vehicles can check and replace your battery for you at a reasonable cost. Replace the battery early and avoid the inconvenience of not having your vehicle start when you need it to.

  • If your battery is always low then check for any source of drainage (Stereo, alarm, compartment lights, etc)
  • Next check the battery itself, if the capacity of your battery is low then it will always be low no matter how much your charge it. This measure is called the cold cranking amps
  • The easiest way to do all of this is to see your mechanic if you are uncomfortable doing it yourself

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