Car battery resistance between the terminals

[DIYspanner]

How many ohms should there on a battery in good condition ?

I'm presuming that if the battery has a bad cell, the resistance will be higher !


opinions please

 

[Burnerman]

Many factors play a part in this one.....you'd be much better off taking the battery for a high current discharge test at a motor factor if you're not happy with yours!
John

 

[bernardgreen]

I'm presuming that if the battery has a bad cell, the resistance will be higher !

The "resistance" may increase or it may decrease depending on the way the cell failed. It will also vary depending on the current being drawn from the battery.

"resistance" or internal impedance has to be calculated from the change in battery voltage when a known current is taken

 

[DaveHerns]

Surely you can't just whack a multimeter on resistance setting across the terminals of a charged battery? Wouldn't it burn out?

 

[DIYspanner]

To be honest, I'm not a lead/acid battery expert.

I was just curious if the internal resistance of a car battery would indicate if all cells were in good condition.

The battery in question is of my uncle's car but he's been to a car factor today. They tested it and the machine said "its time to replace this battery" !

New battery, end of story and a few less £ in the bank gaining interest.

thanks for the information above folks, much appreciated.

 

[DaveHerns]

EBay sellers have some good deals on car batteries

 

[Spark123]

As others have said, the internal resistance is calculated using a load tester. You must not connect a standard ohm meter across a battery, it certainly won't do the meter any good and could go bang.
Normally something like this will do the job: http://www.toolclick.co.uk/p/clarke-battery-vehicle-tester/791?gclid=CKeI5PCY_c0CFcsW0wodlE0DiA (albeit it doesn't tell you the resistance, only the battery condition)