Dead Battery!

[Mopardude]

If I have a dead battery how do I determine if the battery itself is bad or if its the alternator not charging it or some other problem? I am pretty sure its a charging problem. I have noticed lately that sometimes when I start it, that it barely has enough juice to start. Than the other day I started it up and all seemed to be fine so I decided to run over to Walmart in the next town over and put some miles on her to see what happens. When I came back out of Walmart it only had enough juice to turn it over once and luckily that was all it needed. I drove right home parked the car and tried to restart and the battery was completely dead. Than just to make sure it was a dead battery issue I jumpered it off my truck and it started just fine. Beside taking both the alternator out and battery and taking them in to be tested. Is there any thing I can do with a multimeter to help figure out the issue faster?

 

[69signetv8]

Although quite simple, batteries can be confusing. Average life of a battery can be as little as four years and at times if you get a voltmeter you will read 12 volts howerver a cell could be shot and you no longer have the supplied amps to turn the motor over. There are a few checks you can do here to confirm.

1. Depending on your guages....does your Alt light stay on? when running does the Alt indicate a (-) reading or a (+) reading.

2. If possible get anothor good battery and flash up you car. Check your battery to ensure the Alt is putting out 14 volts to the battery. If "yes" it's a good start and confirms your Alt is fine. If "no" you should check right from the Alt to ensure your wires going to the battery are fine.

3. Check to see if you have a electrical bleed or short in your car. Do this by ensuring all your conditions are turned off in your car...(lights, radio, doors closed etc). Take off your (-) battery post and meter between the post and a good ground. If you get any reading on the meter..something is shorting and draining your battery. Remember however some CD/radio will use a small amount of voltage for memory.

4. If you confirm all is fine with your Alt output, wires and connections are fine, you may have to check your voltage regulator. If faulty they can allow your Alt to undercharge or overcharge your battery killing it.

5. Make sure all your connections are clean and tight (battery posts and starter)

6. Lastly, if you take your battery to a shop (they) can bench test it for you this will ensure you if its toast and can not longer hold a charge.

 

[redfastback]

check the alt with the car running, pos + to the alt post and put the neg to ground. if it reads at least 14.0 , your good. now check the battery during cranking, put the pos and neg leads on the battery posts and check it. if it drops below 10.0 volts during cranking, you need a new battery.

 

[Mrmopartech]

As auto tech for some 33years,the easiest way to help determine a electrical problem is start with a battery that is good,one that is fully charged from a nother car,and start from there.If the car starts,you check the chargng system for proper voltage and amps to show the regulator and alternator and working,and the wiring.If this is good,you check for current draw at the battery with the key off and doors closed and keys in your hands and every thing off that you know off.I normally do whats called a parasitic draw test.You remove a battery terminal,and place a multi meter of good grade,OTC/snap-on to the amp setting of 5 amps.The meter should read a digital signal of 0.030-0,050 of one amp as being normal draw for memory for radios and ECM,s.If you get any where near the 0.100 or beyond,you have a good size current draw and needs to be located.That we cover later.Starter draw should be less than 2 volts from a fully charged battery.Meaning that if the battery is showing you have a fully charged battery at 12.5-13.0volts and it drops to less than 10.0 volts when cranking, you either have a low battery or a bad starter,a amp probe shows how many amps the starter is drawing.You can charger your battery for a 24 hour period and have it checked at a auto shop and see if it is holding a charge,while under load,if it fails,install a new one of the maximim rating you can find and the largest size you can fit in the car.Mrmopartech