Battery tester say battery double charged?

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  #41  
Old 09-13-17, 11:42 AM
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good idea, I'll try that and report back, thanks
 
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  #42  
Old 09-13-17, 03:48 PM
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I tried it and the only difference was that the electrical system didn't shut completely off. I could just take the key out and put it back in and try again so I'm starting to think this is pointing to the starter itself, make sense?
 
  #43  
Old 09-19-17, 02:43 PM
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Mechanic said the starter, battery, alternator, negative ground are all fine.
He removed each multiplug one at a time from the fuse panel. Cleaned individually with a wirebrush then contact cleaner.
Works now.
 
  #44  
Old 10-16-17, 07:00 PM
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It's important that all battery cable terminals are clean and bright and tight, not just at the battery itself, but the connection at the block, frame, and firewall. Because of the heavy current involved, even invisible corrosion is enough to cripple alternator. Just a few hundredths of an ohm (hardly anything). You won't notice it at idle but under load the alternator will not be able to keep up. This leads to a chronic undercharge and the battery will not last as long as it might. And the alternator will work overtime and run hot. If you can actually see corrosion and rust on connections and cables, weird growths and chemistry experiments on the terminals etc, they will soon fail altogether and the engine won't start.

With a good DVOM you can do a lot of tests yourself. If doing your own maintenance, buy an external battery charger. It will pay for itself many times over. If you have to jump start a battery keep in mind this is an emergency procedure to get you off the road, back home, etc, the alternator is not designed to recharge a dead or near dead battery. It is a dependable way to smoke the alternator or voltage regulator. Re-charge the battery as soon as practicable with an external charger. Your wallet will thank you. When measuring the battery voltage, the tenths of a volt one way or another are important. The difference between "full" and "dead" is less than a single volt. When someone says "it reads 12 volts!" that doesn't tell you anything. If a battery is only reading 12.1 or 12.2 volts it indicates a problem. In extreme cold it may not be enough. When everything is running right a low battery should never happen.

Modern maintenance free sealed lead lead acid batteries at rest are fully charged at 12.80 volts @ 70F, again a few tenths doesn't sound like much but on a percentage basis it is large. To check alternator output charging turn on all the lights and the heater fan to put a load on the alternator. Rev up the motor to around 2000 or 2500 RPM. Measure the voltage directly at the battery posts. Should see 13.8 to 14.2 volts. In cold weather the battery internal resistance is higher and more voltage is required to charge the battery back up. Below zero somewhere around 15 volts or more is not unusual to reach the same charge level. In very hot weather lower charging voltages are necessary to prevent excessive outgassing.
 
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