Bad Battery???

[1jstrong]

I'm sorry if this question is the same as the one previous mine, but I'm having a problem following that thread.
I had a new starter relay and wiring fixed this past weekend. 1973 Dart 318 wouldn't start, and I thought its was a bad alternator. Took alternator to Autozone and it tested good three times. Still having problems with charging.

So here's the issue, when the mechanic tested the alternator, it tested over 14 volts. When he tested the battery, it only tests out at 12.57 volts. Couldn't he make a test wire to go from alternator to battery + and if the battery starts to test at or more than 14 volts we know it has to be something from alternator to amp meter or from amp meter to battery?

Thanks in advance,

Jason

 

[67Dart273]

A battery which is fully charged and has been allowed to sit long enough to dissipate "surface charge" will test at almost exactly the voltage you posted. This would be, say, a non running car when checking voltage after sitting overnight, with nothing left on in the car.

A bad alternator will not prevent a car from starting and running. In fact, "back in the day" before we had all this fancy EFI nonsense, I've had a couple of times when an alternator went bad.............and I just kept driving it the rest of the day. I knew I would probably "be home" before dark, and did not need lights. A good strong battery will run and re-start a car several times with no alternator

What kind of problems are you having? What does the voltage run "in the car?" running at the battery?

 

[KitCarlson]

If you have a voltmeter and battery charger you can do a fairly good test yourself. First charge the battery. Use the voltmeter to monitor the voltage, if it starts greater than 14.5V, and slowly goes down to 14V, then the battery may be showing signs of sulfation. If it starts out at 11V and slowly increases to anout 14V, it may just be discharged. When you think the battery is charged, often the charge indicator drops to about 2A, and stays steady. Charge time varies with the battery capacity, charge rate, and the charge in the battery when charging started. Typically discharging a battery to 11V is considered a deep discharge, and is not good.

The next step is to remove the charger and let the battery sit unloaded, if in the car, disconnect the ground cable. After an hour measure the battery voltage. The voltage should measure about 12.6 to 12.7V for a good battery. Next step is to connect the ground cable. Rig up the meter to measure the battery voltage while cranking, if it drops below 11V, the battery has a bad or weak cell. When the car is running the voltage should be about 13.8V, but may vary a few tenths.

 

[1jstrong]

What kind of problems are you having? What does the voltage run "in the car?" running at the battery?

Before I had it fixed, I wouldn't start period. The mechanic changed the starter relay and some bad wiring. They called and said it was ready. I went to pick it up and it wouldn't start. He got the charger with the start feature and it started right up. Took it home thinking battery may just be low, so driving it around May give it a charge. Shut it off and gave it a minute and it started up easily.
Over the weekend was busy, so didn't fire it up Saturday or Sunday. Monday morning completely dead, but when I hooked my truck up to it, it started right up. Didn't even need to wait a bit.

So it sounds like the battery, but that reads read over 12 when it is running.

Jason

 

[67Dart273]

OK, what is "it"? What and where are you reading this voltage?

A properly operating charging system on a normal, charged battery will run.......with engine warm, because the regulator has temperature compensation............at about 13.8--14.2. Certainly not less than 13.5 nor more than 14.5. This means with accessories off, engine running fast enough to charge, and battery in good condition (operationally) and fully charged

A low battery might run under this, but you need to determine IF the battery is actually low, or bad, or whether the charging system is the cause.

Does this have the factory ammeter? Converted to voltmeter? Again, with what are you measuring this, where is it connected, and under what conditions.