Technical Symptoms of an overcharged battery?

Hey all,

Long story short:My alternator reads anywhere from 14v to 18v while running. It does not read a consistent number it jumps all over the place. Now my car wont start even though the battery reads 12v. What are the symptoms of an overcharged battery?

Lomg story long: I've been having some weird electrical issues lately that I cant quite pin down and am hoping someone here could offer some guidance. I have a model a roadster with a flathead that just recently has been deciding not to start sometimes. It started as an intermittent problem that has gotten more and more frequent over the past 2 weeks. The first few times it happened I had been out in the car all day and stopped at a gas station on my way home. After filling up the car wouldnt start. I would hit the key and it would give me about a half a turn and then just clicks after that like I had a low battery. Both times this happened i tested the battery with a voltmeter and both times the battery had 12 volts. I had a friend come jump me both times and it started right up. The next time it happened was in the garage and again I had 12 volts but it still wouldnt start, but upon jumping it, it fired right up. Eventually after much hassle I got interstate batteries to warranty my battery. All was good for about 2 weeks after that until I hop in the car and again it wont start. Again I had 12 volts but I hooked it up to the battery charger for about 25 minutes and it fired right up. I'm getting 12 volts to the solenoid from both the battery and the ignition switch. But when I turn the key I'm not getting 12 out of the other side of the solenoid to the starter. I put a new solenoid in it and still am not getting 12 out of the starter side. I also just had the starter rebuilt. I tested the alternator (new powermaster powergen) with the car running and it is all over the place. It is definitely charging the battery but it is not a nice steady number as I believe it should be. It will read anywhere from 14 to as high as 18. Is it possible my alternator is cooking my battery? What are the symptoms of an overcharged battery?

 

12.0 volts is a dead battery. 12.5 volts will usually start a car.

One symptom of an overcharged battery, is that it won't start a car.

Fix the charging system. It could have a bad voltage regulator, or bad wiring.

And learn about what voltage batteries like to operate at. Generally 13 to 14.5v when the engine is running, and 12.5 to 13. x when the engine is not running (they will slowly go down in voltage right after being charged)

 

What in the wiring should I be looking for? All of my connections are clean and tight and none of the wires seem to be visibly damaged

 

Check the battery cable connections and clean before doing any thing else.

Ben

 

If the alternator is new, and it has an internal voltage regulator, and you measure the voltage and it's 18 volts at times, that indicates there is something wrong with that alternator.

When you measured the battery voltage and it was 12v, how did you measure that? Did you use a handheld digital volt meter, and it read 12.0 volts? or some other number? or did you use a dash gauge that showed it was around 12v? If you read the voltage wrong by 1 volt, it's the difference between a fully dead battery, and a fully charged battery. so accuracy is important.

 

A bad or shorted battery will cause the alternator voltage to jump around...replace the battery and then see if the voltage will stabilize...


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Agree, battery is on its way out. Try new battery and check alternator. It should be close to a constant 14.

 

Alternator is a 1.5 year old powermaster. I used a handheld multi meter and it was exactly 12.0

 

The battery is about 2 weeks old. I got my old battery warrantied.

 

Both batteries had the same readings

 

As said earlier battery should be about 12.5 at least. If it slowly creeps lower after a charge it’s not holding the charge.
I just replaced one in my motorcycle that would read 12.5 and slowly drop to 12.2, it would operate the accessories but barely turn over the motor.

 

There are a lot of things that can kill a battery. Loose connections, using more than your alternator can handle, parasitic drains, corroded terminals, faulty wiring and charging system(regulator/alternator). If it’s dying while driving down the road it’s probably the charging system or a connection problem.

 

If the alternator is jumping from 12 volts to 18 volts, it's bad. It shouldn't read over 14.5 volts ever, nor less than 12.5. Sweet spot is around 13.5 volts. Could be the internal regulator gone bad or something loose inside loosing connection. Replace it and you should have your problem fixed.

 

I have had a bad battery that I tried to bring back from the dead with a small amp charger. It jumped around from 13 to 16v and never did bring the battery back. Charger worked fine on a known good one.
It could be a lot of things, slow elimination is the best bet.

 

An alternator that overcharges a battery will usually boil it dry in a short period of time.
As some said, if the battery was suspect to begin with the alternator may be charging at a too high of rate attempting to charge a battery that won't take a charge. I had a customer a few years back who had a weak battery in his truck who would jump it at home in the morning and drive it to work or where ever and then bum a jump to start it when he left. All that charging to try to get the battery back up to capacity was pretty hard on his alternator. He finally took it in when it wouldn't charge enough after he started it to drive it and it would die and not start at a stop light. Cost him a lot more than what a decent battery would have but he was the original cheap Charlie when it came to his vehicles.

When it comes to the WHY the alternator is overcharging you have to look at all the factors as others have said. Wiring up to snuff and wiring connections up to snuff. Voltage regulator not working right as suggested, that would be my guess and not knowing what power master you have it is hard to tell if it has an internal or external regulator or if external does it have the correct regulator on it. Most every one of these aftermarket up grade parts for old engines be it electronic ignition or charging have to have the exact manufactured specified attending piece to work right and you can't run down to Autozone an buy a cheap regulator because you don't want to buy their spendy matching radiator no matter what the self styled expert on Facebook says.
I'd haul the alternator to a good starter/alternator shop and have it tested correctly. To either show that it is bad or show that it is working correctly and there is another factor causing the issue.
Mayve before that I'd check every connection in the charging system from alternator to battery and both to the ignition switch.

 

I have checked the connections multiple times and am confident they are clean and tight. The powermaster is internally regulated. And the battery is 2 weeks old after I got my first battery warranties. I bypassed the ignition switch and it still wouldnt start so I know it's not the switch. I just had the starter rebuilt by a reputable shop this week and replaced the starter solenoid.

 

Do you understand how the voltage a battery will produce, varies with the amount of load (current) on it? When you try to start the car, there is a high current draw from the starter, and the voltage will drop. If the battery is very low on charge, such as at 12.0 volts, then the voltage will drop way down, and the starter motor won't be able to turn. It might even drop it low enough that the solenoid can't stay engaged, which is why you get that "click click click" noise when you try to start a car that has a dead battery. The clicking is the solenoid engaging, and the added load of the starter motor causes the voltage to drop so low that the solenoid can't stay engaged, so it disengages, then the battery has enough voltage to re-engage the solenoid, and the process quickly repeats.

As for what's wrong with your car...if you replaced the battery, and the alternator is not charging it with over 13 volts as the engine is running, then the alternator is not working.

 

Are you sure that the battery has a good ground to the chassis? And the motor to the chassis?
I once noticed my in-dash volt meter needle intermittently going as high as 18v. It was because of a loose + terminal connection, but a bad ground might do the same thing.

 

You may also have another bad battery, or perhaps internal corrosion in a battery cable causing high resistance, I would get the alternator tested, and the battery load tested, and work from there.

 

One thing I didn't see mentioned, is first make sure the measurements your voltmeter is indicating are correct.

Don't misunderstand, it sure sounds like there is a problem with the charging system, but a well known symptom of the modern gee-whiz digital voltmeters is they read way high, when the internal battery gets weak. It can throw you for a loop, maybe this isn't the problem, but it is something to check.

You're getting as much as 18 volts indicated, but the symptoms you describe sound a whole lot like the alternator ain't swapping enough electrons. A week sounds just about right for a battery to go dead in use.

Not trying to beat up on you, but a jump start is OK to get you going in an emergency, get you off the highway and back home, but then the wise thing to do is put the battery on a battery charger. The alternator can't re-charge a dead or discharged battery effectively. Maybe if you drive to Nevada or something like that. A weak battery is hard on them, has been described as like driving on underinflated tires.

 

Just because the battery reads 12 volts or better doesn't mean anything, to actually test a battery you need to put a load tester on it, something in the range of 150 to 200 amp load, if the new battery was to go dead with this test put it on a charger overnight and test it again the next day, if it holds then it should be good and that would tell you the alt is bad, if the batterys load test goes to dead again then its the battery.

 

That's a good point, often overlooked. Both the battery and the alternator need to be tested under load. An easy way to test the charging system is turn the headlights on HI beam and any high current accessories - A/C for you fancy pants hot rodders, heater blower fan, radio, etc. Then run it up to a fast idle. Snap-On tests at 2400 RPM. Measure directly at the battery posts.

High voltage like that, 18 volts is going to outgas excessively, smell bad, bulged case. Pretty dangerous I'd expect.

 

If it will jump start...there is nothing wrong with the starter...sounds like you need to find a battery supplier that has a better quality battery.


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There ya go!! Every thing that can be has been checked. NOTHING WRONG. STILL WILL NOT START. Must be the corona

Ben

 

Ok, I give up.

 

you tried you can not learn the unlearned sometimes

 

Mr Lucas spinning and laughing his ass off

 

You guys wonder why young people arent interested in old cars yet every time a young person posts on this forum with a question they get treated like this. Next time I'll take my questions somewhere else.

 

There was a lot of good info posted to help you. It’s damn hard to solve a problem from a keyboard. Check/test and rule out things until you find the problem and get back with the results.
Thicker skin goes a long way.

 

Test don’t guess!


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