alpine service

A 12v automotive battery contains 6 cells connected in series @ 2.11v each. So a bad cell will leave you around 10volts..not good.

But still I haven't seen to any go bad all of a sudden like that...it is usually pretty obvious when your battery is beginning to suffer..like you would notice the starter cranking over weaker. It is odd for a battery to perform normal and then later that day it is so dead that it can't even be charged or allow the vehicle to take a jump start.

But stranger things are known to happen..as I notice just about every day in this industry something I have never seen nor heard of happens to someone..sometimes with no logical explaination in sight.

Correct me if I'm wrong but in a series circuit if one element burns out doesn't that make an open circuit?  I don't know much about the internal structure of batteries but if one cell was ruined and it's in a series circuit the circuit is done and no power whatsoever.  Seems like it would be 0 volts instead of 10 volts to me?

I can understand the confusion.. it is true that if a series circuit is "open" no current will flow and you have a zero volt situation.

However..an automotive battery as discussed here is dealing with chemical reactions and not so much a "mechanical" connection that has suddenly opened. Usually...and notice I emphasize the term "usually" as a battery or a cell of a standard automotive lead-acid battery starts to deteriorate over time..there is resistance...not an open circuit that occurs..and gradually this resistance increases over a lenth of time...not simply "click...click..boom". This resistance causes voltage loss (or drop if you prefer) but if all the other cells are OK you will have at least 10v available...this is an estimate..a meter reading would be required for accuracy.

Don't forget that a series circuit is techically a voltage divider.....as opposed to a parallel circuit..where the voltage is always equal.

You might want to check out some threads on automotive batteries on this forum or elsewhere to learn more about thier properties and the physics involved. Not really that complicated.

I have witnessed first hand a car battery go from a "working" state to a "non working state" in a short amount of time....but, this was due to the battery exploding when someone left it on a charger way too long...then a spark occured and ...KA-BOOM...not pretty.

But that is an extreme situation....in the real world an automotive battery will weaken over time..not operate normal and the next minute it is totally useless..but I imagine it can and does happen in rare instances.

Whats flying azn?  So physics...fun stuff. I remember stuff like fulcrums and ratios and leverage..mechancal ..but then advanced physics was a brain burner with all that math..not so much.  I wish I remembered any of that lol.

Yeah seems everyone has a battery story or 2...I remember once a customer left a cadillac seville outside our shop for like a month, just left it there. We tried to start it and nothing...when we put cables to it there was major sparks...so eveyone was afraid to jump it. Now since I know a little about batteries I new it was simply acting as a short because it was totally out of juice...just like a cap that sparks when it is discharged and then you charge it without a resistor and burn the gold plating off the connectors..lol

But what I did was go back there at night with jumper cables and held them on the battery and let it spark..in a few seconds it took a charge and the car started. My friend and I took the caddi out that night joy riding and it worked fine. I returned the car later and parked it in a different spot. The next day everyone at work was like "who moved the caddi?? why does it start?? the battery was shorted" Pretty funny stuff.

anyhow..if you can see a cell that is low on "fluid" the battery may still have some life in it...the only way to really tell is if it is a "servicable"battery and you use a hydrometer..which displays the specific gravity..so you know to add acid and/or water...this is normal maintanence on any lead acid battery that is not a "maintainence free" unit. With sealed batteries you can only perform a "load test"...but you also need to make sure that the battery takes a charge..and then is fully charged to get an accurate result.

Another interesting tidbit..and this is on MECP..not that it means anything//but you can measure 12v or better (technically a 12v automotive battery should be 12.66..but thats in a perfect world) and still it can be bad. Don't forget..a batttery needs current reserve..not just voltage to be considered a good battery. I've seen that one stump quite a few people.

But all in all...I still find it is not common for a battery to go from a working state to an "unchargable" state in one trip. It is far more common for a battery to slowly weaken over time...but deep cycling a standard battery will surely speed up the process..but in normal use if the battery keeps dying ....there is your "hint" that things need to be checked. I also find as well that corroded terminals mislead some people into replacing a battery before it's nessecary...I see it quite a bit.