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I have purchased Hyundai Accent diesel 2002 four cylinder from my savings .. its start every morning but not at night when the car's headlights are on. I couldn't start it after one or two attempt . The battery automatically drains when car headlights are on. The starter stops working because of low battery.

I am not sure .. its my battery problem or alternator problem. I've checked my car battery in different car and its work great .. but in my car its only charge on day time when light is off but not when light is on .

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  • On which car you checked you battery? A gasoline cars don't need as much power as diesel, so it could work even if the battery is bad. Alternator is easy to check with multimeter. Just mess the voltage on battery with engine on / off. OFF should be about 12 V and ON about 14 V (+ - 0,5).
    – Watsche
    Commented Jul 23, 2014 at 6:44
  • yes it was gasoline car. okaya.. i will test it first
    – Allex
    Commented Jul 24, 2014 at 16:21
  • can i check car battery voltage with digital multimeter ?
    – Allex
    Commented Jul 24, 2014 at 16:23
  • You can check the voltage, but it won't show you what kind of shape the battery is in. You can always take it to a parts store as most of them can do a load test on the battery.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Jul 24, 2014 at 18:14

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There are three different tests you can do to check your charging system and battery (there are others, but I'll just talk about the big three):

Voltage with engine off

Using a multimeter, select volts-dc on the selector switch, then put the red lead to the positive and black to the negative. For a fully charged battery the reading should be in the 12.5-13.1vdc. If it is much lower than this, the battery is most likely bad.

Voltage with engine running

Using a multimeter, select volts-dc on the selector switch, then put the red lead to the positive and the black to the negative. The reading should be around 14.1-14.5vdc. If it is lower than this, observe what the voltage reads over time. If the voltage drops a little at a time and doesn't regain anything, the alternator is not charging and will need to be replaced. If the reading is over 15vdc (even up into the 16vdc range) the alternator is overcharging. Take it into the parts store and have them bench test it to see what's going on.

Cranking Amps (CA) and Cold Cranking Amps (CCA) testing

Just because the voltage looks good, doesn't mean there isn't something amis with the battery. One other test you can do is to test the CA and CCA the battery should be rated at. Using a tester like this SOLAR BA5 Cold Cranking Amps Electronic Battery Tester, you can tell what's going on inside the battery if you know what it's rated at.

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Looking on the battery labeling should tell you what the CA/CCA are for the battery. Plug the battery tester with red on positive, black on negative. Input which test you want to perform (CA or CCA), then input the rated amperage for the test you've chosen. Click the test button and it will spit out what the actual amount of CA/CCA the battery has. If there is a large difference between what it's rated and what the actual is, the battery will need replaced.

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