Alternator/ Battery light???
- Thread starter flydex28
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flydex28
Senior Member
Ok break thru... I believe I have it figured out now. After a lot of reading and experimenting I found this out. When you start the car the alternator has to recharge the battery to top it off, then when it is fully charged again, it doesnt need 14 volts anymore so it turns the alt down to 12.5. This is why you have the ELD in the fuse box. The ELD measures the total amperage coming from the alt and the computer reads this info. Once the battery is full basically the computer tells the alt to turn down to conserve fuel and wear and tear.
Now if you have your lights or heater on it will always show the correct volts because your car requires the extra power, but during the day when your not using these things it will most likely drop to 12.5ish volts. This explains why when driving to work in the day I kept getting these wierd 12 volt readings and was normal at 14v at night on my way home.
I still need to change my cables out because I to believe that the resistance is too high but at least now i know i can wait till i can get out of town to a stereo shop and get some good cables and connections.
Here is a cool link i found on line from a guy at Southern Illinois University Carbondale dept of automotive technology that explains how the system works.
[FONT=ArnoPro,Bold][FONT=ArnoPro,Bold][FONT=ArnoPro,Bold]http://opensiuc.lib.siu.edu/cgi/vie...8532DQ&usg=AFQjCNHiRVr9DyIeImXPgn6epGpiXOaW7A
[/FONT][/FONT][/FONT]
Now if you have your lights or heater on it will always show the correct volts because your car requires the extra power, but during the day when your not using these things it will most likely drop to 12.5ish volts. This explains why when driving to work in the day I kept getting these wierd 12 volt readings and was normal at 14v at night on my way home.
I still need to change my cables out because I to believe that the resistance is too high but at least now i know i can wait till i can get out of town to a stereo shop and get some good cables and connections.
Here is a cool link i found on line from a guy at Southern Illinois University Carbondale dept of automotive technology that explains how the system works.
[FONT=ArnoPro,Bold][FONT=ArnoPro,Bold][FONT=ArnoPro,Bold]http://opensiuc.lib.siu.edu/cgi/vie...8532DQ&usg=AFQjCNHiRVr9DyIeImXPgn6epGpiXOaW7A
[/FONT][/FONT][/FONT]
Well, this is getting interesting now. I'm going to have to connect up some test gear and monitor my hatch. I've never torn into the ECU with regard to it's potential role in controlling the alternator. I was always under the impression that it monitored only, and the voltage regulation circuitry was with the confines of the alternator - i.e. it operated a a Stand-Alone component.
What I do know is a little about lead acid batteries. Having ran RC models for many years and then racing go-karts with battery powered electronic ignition it's caused a little research on batteries, charging, maintenance, properties, etc.
For lead acid, a very general rule of thumb is the voltage is a good indicator of charge condition. Take a battery that's been sitting 12 or more hours off a charger or alternator and measure the output. 12.5v = ~50% charge condition. Each tenth of a volt over 12.0 volts can convert to a percentage of charge condition. 12.75v is ~75% charge condition, etc.
So, a battery would not be maintained in a properly working electrical system at 12.5v, it takes >12.6v to charge. (Evidently Honda does not consider this to be a problem)
Took a quick look at the link you provided - very interesting material. Educational to me for sure. I'll look at it more in depth tonight for my own education.
Thanks for sharing it.
What I do know is a little about lead acid batteries. Having ran RC models for many years and then racing go-karts with battery powered electronic ignition it's caused a little research on batteries, charging, maintenance, properties, etc.
For lead acid, a very general rule of thumb is the voltage is a good indicator of charge condition. Take a battery that's been sitting 12 or more hours off a charger or alternator and measure the output. 12.5v = ~50% charge condition. Each tenth of a volt over 12.0 volts can convert to a percentage of charge condition. 12.75v is ~75% charge condition, etc.
So, a battery would not be maintained in a properly working electrical system at 12.5v, it takes >12.6v to charge. (Evidently Honda does not consider this to be a problem)
Took a quick look at the link you provided - very interesting material. Educational to me for sure. I'll look at it more in depth tonight for my own education.
Thanks for sharing it.
Last edited:
hey
I have a 92 civic eg...So 1st off I don't know how to post my own questions...but please someone help me! I connect my alternator power wire to the fuse box and my car starts idling funny when it warms up! Alternator is good batt. Is good.... but as soon as I tale the wire off to the alternator it stops and runs fine... what could it be????????
help me please anyone!?
I have a 92 civic eg...So 1st off I don't know how to post my own questions...but please someone help me! I connect my alternator power wire to the fuse box and my car starts idling funny when it warms up! Alternator is good batt. Is good.... but as soon as I tale the wire off to the alternator it stops and runs fine... what could it be????????
help me please anyone!?
The first thing to do is to start your own thread. Then you will be assisted.I have a 92 civic eg...So 1st off I don't know how to post my own questions...but please someone help me! I connect my alternator power wire to the fuse box and my car starts idling funny when it warms up! Alternator is good batt. Is good.... but as soon as I tale the wire off to the alternator it stops and runs fine... what could it be????????
