DIY battery testing?

-Mike-

-Mike-

-Mike-

Soldato
Joined
22 Dec 2002
Posts
10,165
Location
Minehead
Hey all,

I used to know figures off the top of my head but what is a good battery voltage after being sat for a few hours? My civic has been turning over slowly and currently sits at 12.3.

I've got a bosch 110 battery sat on the stairs since trading in my bora but the damn thing is too long unless I remove the battery box which I don't think is such a good idea!

Thanks for any help.
 
As far as I know 12.5 - 12.6 is fully charged and it's dead at around 11.8.

I wouldn't expect 12.3 to have a massive impact on starting. Might be a bit slower due to the colder mornings at the moment.
 
dazz25 said:
As far as I know 12.5 - 12.6 is fully charged and it's dead at around 11.8.

I wouldn't expect 12.3 to have a massive impact on starting. Might be a bit slower due to the colder mornings at the moment.
Click to expand...

Voltage has nothing at all to do with starting (well sort of). I had a battery which read 12.3v but wouldn't turn the starting motor..........turns out under load it was only giving out 8v.

12.6v is the expected voltage of a "normal" good battery which is about 90% charge. I have known some shops reject new batteries delivered with less than 12.6v.

Measuring car battery voltage doesn't give you much usefull information unless you do it under certain load which may vary from one to other battery.
It is important to know what kind of current (Amp) battery is capable to deliver within certain amount of time with minimum voltage of 9.6~10 volts which is enough to spin the engine fast enough in cold temperature and still enough energy for ignition system.

If you get a friend with a multi meter and crank the car over, a good battery should be giving in excess of 10.5v which trying to start the car. Any less and you are getting close to the engine not starting.

As per this video. Battery seems fine at 12.3v yet hasnt got the ampage to turn the car over and volts drop to 4v when trying to start.

http://www.youtube.com/watch?v=Yg4nnsVjMUU

Good info here on battery charging

http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery
 
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