Car battery test

[purplemonkey]

Hi, been having some problems with my battery recently so took it to local battery store where they tested it. They were able to tell me it needed a full charge, the battery is rated around 600 and it showed 450, think this is an amp related figure.


Anyhow my question is there a way to do this check at home, say with a multi meter? Or are these guys using a special tool/meter?

 

[Belle427]

They may have carried out a load test on the battery, difficult to do at home without the right equipment.
Have a read of the link below, it shows some basic tests you can do at home.
5 years seems to be about the life of most run of the mill batteries these days.
http://www.aa1car.com/library/2003/us20310.htm

 

[purplemonkey]

Thanks it's a good article. Battery is only a year old, but looks like it runs down due to infrequent use.Will have to start keeping an eye on it and manually charging when I can.

 

[Peter.N.]

A car battery is designed to be kept almost fully charged and will not stand being run flat many times before a lot of capacity is lost, you need a deep cycle battery for that.

You can load test it on the car by operating the starter with a meter connected across the battery, I don't know what the permissible voltage drop is but I would think if it drops much below 10 volts its on the way out, a diesel will draw more current so the voltage could drop lower.

Providing the car is used reasonably regularly the battery should be OK but if its left for weeks it will slowly discharge, if the car is not going to be used for sometime its best to disconnect the battery.

Testing a battery off load with a meter doesn't give you much of an indication of its condition, a nearly flat battery will still read 12 volts or more.

Peter