I think my battery is going bad I want to test it using a voltmeter, do I put the volt meter on ac or dc?? Also how much should the volt meter read....

 

anyone???

 

Dunno that a voltmeter is going to tell you much, as you won't be putting a load on it. Take it down to your local Pep Boys/VIP/Autozone/Sears, they'll test it for free.

As for the the voltmeter...

AC is Alternating Current, found in your house. DC is Direct Current which is stored in batteries, and found in your car. To check voltage set the meter to 15V, well that's what it is on my meter. This way you can get a good reading on the actual volts. Red to hot, and black to ground.

 

voltage is the potential difference across two points, and is constant, load or not

all you do is put your multimeter on voltage (DC) and place one lead on the positive terminal, and the other lead on the negative terminal...

it'll tell you a positive or negative value depending on which way you have your leads orientated... value some be +/- 12

 

I stand corrected, after I poked around. But you need a digital meter capable of detecting .05v variances.
Found this chart:




Open Circuit Voltage
Approximate State-of-Charge at 80°F (26.7°C)
Hydrometer Average Cell Specific Gravity
Electrolyte Freeze Point

12.65
100%
1.265
-77°F(-67°C)

12.45
75%
1.225
-35°F(-37°C)

12.24
50%
1.190
-10°F(-23°C)

12.06
25%
1.155
15°F(-9°C)

11.89 or less
DISCHARGED
1.120 or less
20°F(-7°C)

 

ok well i went to my mechanic and he cheked it for free, apparently my battery is bad which is causing my car a few cranks to start, ill be replacing it tommrow thanks for the help fellas

 

Actually, to tell whether the battery is good or bad, you need to measure it under load... And bad bettery drops quite a bit of voltage when loaded.

 

yeah i am going in to the shop tomorrow to check mine... i am almost certain it needs to be replaced... better not be the alternator AGAIN![:@]

 

Hey fiirkan, did you read the faq I posted about car stereo's load on the charging system? How high end is your system? That could be killing your Alt/battery.