Checked my car battery....

tonyyeb

tonyyeb

tonyyeb

Soldato
Joined
31 May 2006
Posts
4,239
Location
127.0.0.1
Hi all

Got a new toy for xmas and have just tried it out. Its a car battery and alternator tester. I tried it on my 02 Ford Focus Zetec 1.6 and it read 12v - LOW. Got out my multimeter and it read 12.4v. Tried the multimeter on the Mrs 06 Fiesta Zetec S (1.6) and it read exactly the same. Is the battery tester wrong to say LOW and it should say OK really or is there a problem with both batteries?

Cheers
 
Best way to test a battery is amperage not voltage, and an alternator should generally give out 13.3v-15v.
 
moss said:
Best way to test a battery is amperage not voltage, and an alternator should generally give out 13.3v-15v.
Click to expand...

No it isn't, what the OP has done is correct. You test a battery by the voltage. To the OP, are you sure it isn't the 'alternator' part of the tester that is reading 'LOW', as this would make more sense.

The average idle voltage of a automotive battery is 12 ~ 12.5v. Any lower than 11.5v and it needs a charge.
 
tonyyeb said:
Hi all

Got a new toy for xmas and have just tried it out. Its a car battery and alternator tester. I tried it on my 02 Ford Focus Zetec 1.6 and it read 12v - LOW. Got out my multimeter and it read 12.4v. Tried the multimeter on the Mrs 06 Fiesta Zetec S (1.6) and it read exactly the same. Is the battery tester wrong to say LOW and it should say OK really or is there a problem with both batteries?

Cheers
Click to expand...

Was this with the engine running?

The volt gauge in my car shows 12.5v when the engine is off and 14v when it's running.
 
splitz said:
No it isn't, what the OP has done is correct. You test a battery by the voltage. To the OP, are you sure it isn't the 'alternator' part of the tester that is reading 'LOW', as this would make more sense.
Click to expand...

Strange using the £400 tester at work, the battery test measures the amperage not the voltage and tests the alternator using voltage.
 
Sure, but how do you suggest the OP tests the amperage of his battery? The most accurate way is to test the voltage drop of a battery when a given measure of current is drawn but generally the voltage of an idle battery is sufficient enough.
 
splitz said:
Sure, but how do you suggest the OP tests the amperage of his battery? The most accurate way is to test the voltage drop of a battery when a given measure of current is drawn but generally the voltage of an idle battery is sufficient enough.
Click to expand...

Thats fair enough, he cant really test the amperage properly, but im always required to do amperage tests against the CCA of batteries at work, I use a midtronics battery tester.
 
My Battery(original on an 02 plate) was only just turning the engine over on a morning a while back, took it to motorsave and their tester said low , took the battery out and gave it a 4amp ish overnight charge. Even though its branded maintanence free the caps twist out and the cells were bone dry , wasnt expecting much but after topping back up with battery water its back to normal.
 
Hi Guys

Thanks for all the replies. The engine was not running. The battery tester said to ensure the engine was off and had been for a while.

I have checked the tester again and 12V is LOW and 12.5V is NORMAL so i guess they are both just 0.1V from being normal according to the tester.

Thanks again
 
You must log in or register to reply here.
Back
Top Bottom