Failure modes of batteries

[micky 32]

I have noticed there are different failure modes of batteries. For example my 6 year old AGM start stop battery has an issue where it has lost some of it’s CCA that it cranks slowly along with low voltage cranking in cold weather. However it has lots of reserve power. I can leave parking lights on or listen to the radio for an hour and the car will still start.

When my partners battery (flooded) failed in her car it was the opposite. It cranked the car nicely even in cold weather but if she sat in the car listening to the radio for half an hour and then tried to start the car it was “click” no start.

What is happening in the batteries that cause the different failure modes?

[bcroe]

I have noticed there are different failure modes of batteries. For example my 6 year old AGM start stop battery has an issue where it has lost some of it’s CCA that it cranks slowly along with low voltage cranking in cold weather. However it has lots of reserve power. I can leave parking lights on or listen to the radio for an hour and the car will still start.

When my partners battery (flooded) failed in her car it was the opposite. It cranked the car nicely even in cold weather but if she sat in the car listening to the radio for half an hour and then tried to start the car it was “click” no start.

What is happening in the batteries that cause the different failure modes?

Do check, that the starter is good. I have replaced the brushes at
100K, but that will vary widely. Bruce Roe

[micky 32]

No starter ok both batteries tested they are telling me to ‘replace’. I suppose the best way to explain is water pipes. With my agm battery it’s like the tank is full but my pipe has narrowed with gunk. The other battery’s water pipe is fully open but the tank is low( the battery is fully charged)

My agm battery is like a new battery when it’s anything over 15degrees C

i was just wondering what is going on inside the batteries that present two different faults.

[littleharbor2]

Pictures? Are your cables and terminals clean, tight?

[micky 32]

Yes. The batteries are at fault. . They are worn out. My battery reads circa 400cca. It’s rated for 680 cca. My question was what has happened internally to both batteries that have 2 different symptoms of end of life.