How many volts should a fully charged battery read?
08-22-2001, 06:36 AM
#11
New Member
Join Date: Jul 2001
Posts: 191
Likes: 0
Received 0 Likes
on
0 Posts
I was a little abbreviated in my response...
It's been a while since I researched this I thought the chain of events was...
1. Alternator put out around 14 volts of AC
2. Diodes converted the AC sine wave into a DC pulse
3. The voltage regulator monitored voltage to the battery to maintain a charge, regulating the voltage from 14 something down to 12.
Amperage output of the alternator was important because accessories really run off the alternator when the car is running, supplimented by the battery. If there is not enough oomph (technical term) in the alternator the extra needed amperage was drawn from the battery, running it down. Since our alternator is not keeping up with the accessories, it certainitly won't keep up with charging the battery.
If I'm way out on this I'm sure the good folks here will let me know.
1. Alternator put out around 14 volts of AC
2. Diodes converted the AC sine wave into a DC pulse
3. The voltage regulator monitored voltage to the battery to maintain a charge, regulating the voltage from 14 something down to 12.
Amperage output of the alternator was important because accessories really run off the alternator when the car is running, supplimented by the battery. If there is not enough oomph (technical term) in the alternator the extra needed amperage was drawn from the battery, running it down. Since our alternator is not keeping up with the accessories, it certainitly won't keep up with charging the battery.
If I'm way out on this I'm sure the good folks here will let me know.
08-22-2001, 06:58 AM
#12
Elder Member
Join Date: Jul 2000
Posts: 23,167
Likes: 0
Received 0 Likes
on
0 Posts
I've never seen or heard of an alternator that did not use a voltage regulator.It may be sperate or
internal.
For those that want to know how automotive charging systems work ,see the link.
I'm not about to do that much typing.<ul><li><a href="http://www.howstuffworks.com/framed.htm?parent=question324.htm&url=http://www.autosite.com/garage/encyclop/ency11a.asp">http://www.howstuffworks.com/framed.htm?parent=question324.htm&url=http://www.autosite.com/garage/encyclop/ency11
For those that want to know how automotive charging systems work ,see the link.
I'm not about to do that much typing.<ul><li><a href="http://www.howstuffworks.com/framed.htm?parent=question324.htm&url=http://www.autosite.com/garage/encyclop/ency11a.asp">http://www.howstuffworks.com/framed.htm?parent=question324.htm&url=http://www.autosite.com/garage/encyclop/ency11
08-22-2001, 06:59 AM
#13
Elder Member
Join Date: Mar 2000
Posts: 13,440
Likes: 0
Received 0 Likes
on
0 Posts
Some facts
The alternator has to put out more voltage than the battery. You can not have current flow if there is not a voltage differnece. That is why the voltage from the alternator is higher than the rated voltage on the battery.
The alternator is designed and sized to supply all the equipment on the car with current when the car is moving. The battery is there to make up for the difference in power required when the car is idleing or off - and to provide the power to start the engine.
The voltage regulator is used to control the voltage to the accessories. It will step down the volatge to provide a constant 12 volts to things like the lights, radio, window motors, etc. Inadditon, things like radios, phones, etc that need even more voltage regulation will have their own power regulators to control spikes and noise that are on the lines that come from the alternator, and electric motors when used.
Reggie
98.5 2.8QMS
The alternator is designed and sized to supply all the equipment on the car with current when the car is moving. The battery is there to make up for the difference in power required when the car is idleing or off - and to provide the power to start the engine.
The voltage regulator is used to control the voltage to the accessories. It will step down the volatge to provide a constant 12 volts to things like the lights, radio, window motors, etc. Inadditon, things like radios, phones, etc that need even more voltage regulation will have their own power regulators to control spikes and noise that are on the lines that come from the alternator, and electric motors when used.
Reggie
98.5 2.8QMS
08-22-2001, 07:07 AM
#14
Elder Member
Join Date: Jul 2000
Posts: 23,167
Likes: 0
Received 0 Likes
on
0 Posts
It's 2.1 per cell which would be 12.6 Actually it is a bit more than 2.1 per cell and a fully.......
...charged lead acid type 12v automotive battery can be 12.7 fully charged. Some automotive gell cell batteries can be has high as 12.9 fully charged.
08-22-2001, 07:30 AM
#18
AudiWorld Expert
agree with everything...
but 14.4V DC is supplied to the battery. It isn't clamped down to 12V.
When you said: "Since our alternator is not keeping up with the accessories, it certainitly won't keep up with charging the battery.", did you mean this as a general statement, or are you having problems? Do you mean with a stereo system installed? I had a pretty elaborate stereo system and had no problems that required me to change my alternator due to insufficient supply abilities.
When you said: "Since our alternator is not keeping up with the accessories, it certainitly won't keep up with charging the battery.", did you mean this as a general statement, or are you having problems? Do you mean with a stereo system installed? I had a pretty elaborate stereo system and had no problems that required me to change my alternator due to insufficient supply abilities.
08-22-2001, 07:49 AM
#19
Elder Member
Join Date: Jul 2000
Posts: 23,167
Likes: 0
Received 0 Likes
on
0 Posts
OK, I didn't say it did. What an alternator generates and when is somewhat variable.......
....depending on the car. 14.5 is usually the max. with the regulater working. It will produce more if the regulator is bypassed when doing a charging system check with a tester.
08-22-2001, 07:51 AM
#20
Junior Member
Join Date: Jan 2001
Posts: 819
Likes: 0
Received 0 Likes
on
0 Posts
Almost any DC regulator....
Output Voltage goes through a set of resistors that form a voltage divider. This divided voltage is then fed back (negative feedback) to the input of a differential comparitor. The comparitor compares a reference voltage at one input to the sum of the negative feedback and input voltage on the second input; the object of the differential amplifier is to adjust its gain so that the difference between the reference voltage and the input+feedback voltage remains at zero; therefore, the gain is adjusted to maintain a constant DC output voltage.