alternator and voltage question:

[R22tech]

I have an 85 and use an Escort 8500 radar with voltage reading. I realize the voltage will vary at any given time, but what would be the range for a properly functioning alternator/voltage regulator/battery on a car that is driven about once a week and mostly short drives? I'm trying to figure out if I'm in the danger zone on my alternator as I saw 14.? volts on the radar reading last night. It usually ranges around 12.9-13.8. I also had my seat belt buzzer come on for no reason a couple of weeks ago, buzzed for a few seconds then stopped. I heard something about these being related.

[HawgRyder]

I would check all your main connections in the charging circuit.
If the battery is not taking the load...yes the voltage will go higher.
This can be seen at night very easily...the lights will get very bright...just before they start to burn out!
Bob

[carnut169]

Doug- my 87 varies between 11.9 and 13.4. It is usually right around 12.9/ 13.0.
I am suprised you are not interested in the endurance karting....
things go over 50mpg and pull 1.2g's!

[911pcars]

Typically, the charging system should output around 14+ volts (14.4 or so) when the system is used (headlights, r.w. defroster, A/C and reg. fan, dome/glove box lights, etc.). A fully charged battery (engine OFF) should create 13.2 volts. If your system is putting out less when driving, then the battery is discharging, albeit slowly.

Sherwood Lee
http://members.rennlist.org/911pcars
www.seinesystems.com

[carnut169]

Sherwood's info makes me question the 8500's accuracy. The reading has not changed since you showed me how to display volts on the 8500 (Doug) and I drive my car only a couple times a week- if the battery was discharging (even slowly) the car would not start after several months.... right?

[bjola]

Yes, your voltage reading during charging should read approx 14.5 V for a healthy system. If you are down to below 13 you will not charge your battery to full.
You will only discharge your battery if voltage is below 12 V.

[R22tech]

So, I'm o.k. then? What would be the voltage point that is considered too high? I just want to make sure I get this possible problem fixed before any damage could occur. Any comments on the seat belt buzzer going off for no reason?

[911pcars]

"You will only discharge your battery if voltage is below 12 V."

Actually, a fully-charged 12 volt battery should create 13.2 volts (6 cells x 2.2 volts). 12 volts from a 12 volt battery indicates some degree of discharge.

Sherwood

[bjola]

Sorry Sherwood, it was late I was tired...your right about that 13.2 volts

What I ment was

you got two sources for deliviering power to your cars electrical system, the battery and the generator. The one with the higher voltage will provide the power.
You will always discharge your battery when cranking the engine, the longer you crank the more you discharge.

#1 if the generator supplies 14+ volts it will be used to power your car systems and also charge the battery back to full.

#2 if the generator supplies 13 volts it will be used to power your car systems (after cranking battery voltage will be below 13 volts) and also charge your battery, but not to full, ie you will have less capacity next time you try to start the car.

#3 if your generator supplies 10 volts you will use the battery to power your car systems until battery voltage is down to that 10 volts then the generator will power your car systems and keep the battery at the state of charge that exists at 10 volts battery voltage (very low)

#4 if your generator dont work you will drain your battery to flat!

Hope this explain my somwhat "hard to understand" earlier post

Is'nt this electrifying?

Bjorn