Dead Car Battery?

JoeJester

Joined Apr 26, 2005
4,390
I suspected a bad battery in my car, cause by high Internal Resistance. My automatic charge exhibited the same properties yours did. The alternator appeared to work, exhibiting 13.8 V, but I saw it lower on my digital meter. There are times the analog meter is the better choice.

So, I knew under load, the voltage dropped sufficiently enough that the battery was defective. I didn't have the test equipment to test everything, and the two places I visited that had it couldn't connect it. One wanted me to wait four hours ... that wasn't happening.

I took it to a shop that had ASE mechanics, you know, those certified types. Yes, I paid more than I had to, but I did contribute to the economy, as their family has to eat too.
 

tcmtech

Joined Nov 4, 2013
2,867
I'm going to guess and say it has a weak alternator plus either one or more burned out glow plugs or possibly a defective glow plug control module.

If its none of that I am going to suspect the fuel injection system or the whole engine is worn out.
 

cork_ie

Joined Oct 8, 2011
428
Check the voltage at the alternator between the main positive terminal and the casing. Turn all consumers (unnecessary load) off. It should be greater than 14.2 V with engine running at above 1000 RPM.
If your voltage at the alternator is low, check the belt is tight and pulley is in good condition., after that you will need to remove the alternator and have it repaired.
If the voltage at the alternator terminal & casing is correct, then you need to check for voltage drop in the charging circuit.
Switch on headlights, heated screen & interior blower fan to load the system , then check for voltage drop between alternator casing and battery negative , maximum voltage drop should be 0.2 V on the negative line. If the voltage drop is high check the engine to body earth strap.
Then check for voltage drop between the alternator positive terminal and battery positive terminal. The maximum voltage drop should normally be 0.25V, but 0.3V may be acceptable if there is a fuse in the charging circuit.
Sometimes the alternator output cable is routed to the starter solenoid and thereafter shares the battery positive supply cable to the starter. It is common enough to have a poor connection where the two cables are attached to the starter solenoid and is well worth checking.
 

MrAl

Joined Jun 17, 2014
11,396
Hello there guys,

This is one problem i never got to figure out exactly. The alternator only puts out 13.5v to 14v which is what is happening here too.
My guess is that the older batteries would charge ok with that voltage, but the newer ones require a higher voltage to charge fully.

I was able to prove that a higher voltage does charge the battery better and therefore lower the internal resistance. This was done by bringing the battery into the house and charging with a power supply. The current was low, maybe around 2 to 4 amps, but left on until it dropped lower and lower, maybe 8 hours or more. The charge voltage was always 14.2 in this case.
After reinstalling the battery in the car, the voltage stayed higher for a month or two, then would require that in house charge again or else it would drop lower, and the car would not turn over as well.

So could the main problem be that the battery is a newer type being used in an older vehicle?
 

Lestraveled

Joined May 19, 2014
1,946
I sincerely doubt it. Battery chemistry has not changed much is a long long time. Automotive batteries have a very narrow performance range. High cranking amps and low average current have been the norm. To desulfate a lead acid battery requires the charge voltage to come just below bubbling or 14.4 volts.
 

shortbus

Joined Sep 30, 2009
10,045
I sincerely doubt it. Battery chemistry has not changed much is a long long time. Automotive batteries have a very narrow performance range. High cranking amps and low average current have been the norm. To desulfate a lead acid battery requires the charge voltage to come just below bubbling or 14.4 volts.
But not all batteries in cars today are wet/flooded cell types any more. My 2004 Pontiac Gran Prix came from the factory with an AGM.
 

Dr.killjoy

Joined Apr 28, 2013
1,196
But not all batteries in cars today are wet/flooded cell types any more. My 2004 Pontiac Gran Prix came from the factory with an AGM.
True but vast majority of them are still flooded/wet.. I have always used wet/flooded batteries and tried 3 Optima batteries and they where junk..
 

Dr.killjoy

Joined Apr 28, 2013
1,196
Hello there guys,

This is one problem i never got to figure out exactly. The alternator only puts out 13.5v to 14v which is what is happening here too.
My guess is that the older batteries would charge ok with that voltage, but the newer ones require a higher voltage to charge fully.

I was able to prove that a higher voltage does charge the battery better and therefore lower the internal resistance. This was done by bringing the battery into the house and charging with a power supply. The current was low, maybe around 2 to 4 amps, but left on until it dropped lower and lower, maybe 8 hours or more. The charge voltage was always 14.2 in this case.
After reinstalling the battery in the car, the voltage stayed higher for a month or two, then would require that in house charge again or else it would drop lower, and the car would not turn over as well.

So could the main problem be that the battery is a newer type being used in an older vehicle?
The issue you are having is that the alternator is not the charging the batteries fully .. My advice check cables and if the alternator is easy to take out then take to local Advance Auto or Autozone for free testing ...Also you can drive your car to Advance Auto and they can test your battery and charging system right on the car and give a diagnosis..
 

MrAl

Joined Jun 17, 2014
11,396
Hi,

Thanks for the replies/ideas.

I have wondered about the difference between the AGM and 'normal' batteries too. Is there a difference in the required charge voltage level or not?

As to the Autozone idea, i actually did that a while back. I had the battery checked and the charging system checked and they tested GOOD.

The problem then was that the battery would charge nicely for a while, but not quite enough. After maybe 2 months the voltage would fall lower and lower, down as low as 11.5 volts. I know that is not right for a lead acid battery. After taking it into the house and charging with a decent power supply at relatively low current for at least 8 hours, the voltage would read "14.2" and then fall gradually down to around 13.8v, which seemed nice to me. The car would then turn over really well when starting.
But then after about 2 months the same thing would happen again. Down to 12.5v, 12.4v, 12.3, 12.2, 12.1, 12.0, 11.9, etc. I dont know fi there was a lower limit (like 11.0) because i never let it get that low, but the car turned over slower and slower and the crank voltage fell lower and lower (down to 8v as in the original thread problem). The car turned over, but barely after a while.

I actually have records of the voltage over several months, taken every single day so i could show these if needed. But the description above is fairly accurate as to the way the voltage dropped over time.

I should also mention that i dont use the car every single day like most people do. The car may site for 2 days without use. But i would not think that the battery would have to be charged every single day just to keep up. Also, the charge voltage was not very high, only 14.0 volts measured with a fairly accurate meter which was tested with a good 5 digit meter.

My newer vehicle (used not really new) is a 1998 model, but this is showing signs of the same thing now. The charge voltage on this one varies from 14.0v down to about 13.5v but that lower reading could be a little higher like 13.8v. But that does not seem high enough either.
What happens is the voltage will read 13.0v when the car is turned off, but then as it sits for a day or two it will drop down as low as 11.5v.
I think the charge voltage should be at least 14.2v dont you guys?

For the older car which i got rid of now, i just replaced the alternator in that one too. That's when i first noticed that the new alternator only put out 14.0v instead of 14.2v. With the old alternator it was 14.2v before it died on me of course.

Thanks again for the ideas, and any more would be nice too.
 

Dr.killjoy

Joined Apr 28, 2013
1,196
I am not sure if your not listen or what the problem is here.. I work on cars for a living and your making this way more complicated than it needs be ... You can provide all the information you want but not listening and doing what is asked to help get a resolution is just wasting time ..
Are you going to help us help you ???
 

tcmtech

Joined Nov 4, 2013
2,867
If you are not getting a fairly stable 14 - 14.4 volts at the battery or at the alternators output stud you have an alternator issue. Plain and simple.

As for the daily voltage dips vehicle have a constant parasitic load on them even when the key is off so it's normal to see a few millivolt drop per day. A good battery after a reasonable drive should sit at around 12.6 - 13 volts for most of a day or more before showing the bit by bit drop.
 

ian field

Joined Oct 27, 2012
6,536
I checked the voltage while its charging and its reading 15V but ammeter shows almost 0A.
A healthy battery will start off with high charging current that slowly sinks down to a low value.

A sulphated battery is pretty much a capacitor that doesn't hold much charge.

There are ways of shifting sulphate - but they'd violate the T&C on this forum. Add to that the fact that the offending sulphate was part of the active battery plates, the battery capacity will never recover to what it was.
 

MrAl

Joined Jun 17, 2014
11,396
I am not sure if your not listen or what the problem is here.. I work on cars for a living and your making this way more complicated than it needs be ... You can provide all the information you want but not listening and doing what is asked to help get a resolution is just wasting time ..
Are you going to help us help you ???
Hi,

What are you talking about? You suggested taking it to Autozone, and i did that, and they state that it is GOOD.
As others have suggested, it's not really good because the voltage is not high enough.
So you think the alternator is shot then, in this second car too?
 

Dr.killjoy

Joined Apr 28, 2013
1,196
Hi,

What are you talking about? You suggested taking it to Autozone, and i did that, and they state that it is GOOD.
As others have suggested, it's not really good because the voltage is not high enough.
So you think the alternator is shot then, in this second car too?
Here is a battery charge state chart

Check this out
http://www.aa1car.com/library/charging_checks.htm
Also whenever a car sit for a while and not used then a battery tender should be used to keep the battery fully charged..
 

ian field

Joined Oct 27, 2012
6,536
Hi,

What are you talking about? You suggested taking it to Autozone, and i did that, and they state that it is GOOD.
As others have suggested, it's not really good because the voltage is not high enough.
So you think the alternator is shot then, in this second car too?
I'd put it on a good quality charger overnight and see what resting potential it sinks back to when taken off charge.

If its sunk below about 11V after standing a week; its probably scrap.
 

Herrydas

Joined Jun 3, 2015
4
Replace the battery then check alternator, it works well or not. To find out battery is good check headlight and engine crank power.
 

bwilliams60

Joined Nov 18, 2012
1,442
Showing 12.3 after a full charge means you have one shorted cell in the battery.
If it is a wet cell battery with caps. You can pour out the acid and rinse the cells out with distilled water, the refill the cells with acid you poured out. That may remove the short if caused by sediment. If the plates are warped and touching or it is SLA type then best use of your time would be buying a new one
12.3 Volts does not mean the battery has a shorted cell. It means it is roughly 70% charged and needs to be recharged and tested properly. A shorted cell would be significantly less than 12.6 VDC. Draining a battery is not a smart practice. Sediment floats to the bottom and is caught in the bottom tray as designed
I checked the voltage while its charging and its reading 15V but ammeter shows almost 0A.
Something wrong with ammeter. If you are pushing 15VDC into a battery, you are also pushiing around 35-40 amps in a 650CCA battery.
If your "dead" battery has a higher internal resistance, the 6 ampere charge will start charging the battery, and as the battery charges, with a constant internal resistance, the voltage at the battery terminals will increase to 13.8 volts quickly and the charger will shift to the trickle or a lower charge rate. That is what you are seeing.
Depends on the battery charger being used. Some will just keep on climbing in voltage. Basis for sulphation test using the Three Minute Charge Test.
 

bwilliams60

Joined Nov 18, 2012
1,442
Battery measured 12.65V which is fine but alternator measures 13.5V when car is at idle and 13.3V when at 2000RPM.
Belt or belts slipping/Excessive voltage drop on positive or negative side of circuit
If your charging system regulator is out of whack it could be the cause of the low charging voltage you see with engine running.
Voltage regulators in vehicles are set between 13.6 - 14.4 VDC. A voltage regulator does not drop in voltage when RPM is increased.
I'm going to guess and say it has a weak alternator plus either one or more burned out glow plugs or possibly a defective glow plug control module.
If its none of that I am going to suspect the fuel injection system or the whole engine is worn out.
Really?????????
So could the main problem be that the battery is a newer type being used in an older vehicle?
No, does not matter. You have another problem. Your battery is sulphated. Causes can range from buying batteries that were on the shelf for a long time to the fact that it sits for a few days and then you make short trips and never get it fully charged again causing your voltage to drop each time. You could also have a parasitic draw that is pulling your battery down constantly and slowly. This would probably be the most likely cause.

Batteries in a low state of charge can be that way for a number of reasons. One of the biggest is sulphation. A car battery has an average life span of 5 years and that includes the time it sits on the shelf at the parts department before you buy it. Modern day handheld testers are not valid in many ways and if they are not tested by carbon pile, there is no way of knowing for sure if they can handle the cranking motor load. Sulphated batteries cannot be resurrected or brought back to life successfully despite all the hoopla on the Internet saying they can. Sulphation is a crystalline structure that when broken away from the plate by "blast" charging, takes part of the sponge lead or lead peroxide with it, reducing the plate surface area. The original battery in this story, was more than likely sulphated and at the end of it's life. As for battery charging, standard lead acid batteries must not be charged over 15.5 VDC or they will start to boil. AGM and GEL batteries are in the area of a maximum of 13.8-14.1 VDC respectively. Higher than that and they will sizzle. They are much better at deep cycling that SLA batteries.
Charging system voltages can be reduced at higher RPM by a number of factors as I mentioned, but often times when an alternator has been subject to a bad battery, it will either fail or it will fail soon after the battery has been replaced. It has burnt itself out trying to charge a dead battery and has worked really hard to do that. As you all know, diodes do not like heat. Poof.
Glad to hear you have your glow plug issue sorted out. You could do that yourself with an inductive ammeter test. Simply check each glow plug current draw when the key is cycled. They should all be the same. Best to replace as a set. The others will follow shortly.
Cheers!
 
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