9 votes
Accepted

I shorted the alternator for a second with a multimeter set to measure current

No, you most likely didn't mess anything on the car up, though you might have fried your multimeter. If the vehicle still runs and nothing seems messed up, more than likely nothing is. Something you ...
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6 votes
Accepted

What is surface charge and how does it affect battery testing?

I have often heard this term as well, but have never known the technical reasons or the actual root cause of what is known as a "surface charge". To figure it out, I took a gander at a website called ...
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4 votes

New AGM 12V battery at 10.8V - charger says it is full

I've had problems charging AGM batteries in the past. Just for this purpose, I keep a small 12v lead acid battery around and put it in parallel with the AGM battery, then apply the charger. This ...
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4 votes

I shorted the alternator for a second with a multimeter set to measure current

You did no damage to the car with this. If your DMM does not have a fuse, you may have ruined the amp part of the DMM. If you measure a known amp source and get an accurate reading your good to go. If ...
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  • 2,692
3 votes

New AGM 12V battery at 10.8V - charger says it is full

Generally, a 12V lead acid battery going straight from around 10.8V to "fully charged" is indicative of one of the 6 cells being completely dead and acting as a near-short with whatever its ...
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3 votes

Alternator health check

The voltage readings sound fairly normal to me. Also, since you don't get fluctuating voltages depending on RPM, I would suspect the voltage regulator is also good. I would check elsewhere. ...
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2 votes
Accepted

Brand new lead acid car battery reads only 12.33v. Is it faulty?

If the battery will start the car and is over (or in the neighborhood of) 12.5vdc, I doubt you have anything to worry about. The great thing about most battery manufacturers is, their warranty usually ...
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2 votes

basics of charging a Lead Acid battery?

While the answer by wilkvolk is accurate for recharging a battery, I'm pretty sure you won't need to go through all of that to do what you need it to do. If the battery is hooked up to your vehicle ...
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2 votes
Accepted

Left car battery "tipped" for a few months--is it safe to use?

No, you will need to top up the liquid level to above the plates. I suggest that you check the ph of the existing liquid so it can be matched. A good battery shop can mix the acid / water to that ...
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  • 34.4k
2 votes

Battery level indicators in dashboard of four wheeler vehicles

Estimating the state of charge of a battery is generally a non-trivial engineering task. In this regard, Li-Ion batteries in the smartphones are (somewhat) easier than the lead-acid batteries used in ...
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  • 1,952
1 vote

Battery level indicators in dashboard of four wheeler vehicles

There will be a battery indicator in the instrument cluster, but it will not indicate how well charged the battery is; the light is not a "battery level indicator" as in the title to your ...
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1 vote

New AGM 12V battery at 10.8V - charger says it is full

You are measuring the voltage incorrectly. The proper way to measure voltage is not to apply a huge current (starting a generator), for multiple times, and measure the voltage immediately after that. ...
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  • 13.7k
1 vote

I shorted the alternator for a second with a multimeter set to measure current

No parasitic drain, your alternator is charging your battery, everything is working. You are good. You need a new battery.
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  • 838
1 vote

AGM Battery - Residual Voltage?

An AGM battery is a lead acid battery, it's best to not go too far down the rabbit hole of comparing a regular liquid electrolyte battery to AGM, there's no practical difference when you are measuring ...
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1 vote

basics of charging a Lead Acid battery?

Step 1 Wear protective gloves and goggles before you rebuild the cell structure of your 12- volt battery. You need to access the cell reservoirs that contain highly toxic sulfuric acid that ...
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1 vote

Car battery at 11.8v in the morning and 12.5v after 20 minute drive bad?

Automotive batteries are designed for infrequent, brief high amp output with minimal parasitic load. Regular use as a power supply battery providing sustained low amp load will lead to a reduced ...
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  • 1,165
1 vote

Flat Battery, heath is down but charge is fine

Car batteries only last a certain length of time - average is about 5-6 years although it will depend on the climate and the type of use the car gets. What the AA are telling you is that your battery ...
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  • 28.6k

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