Voltage Problem?
Thread Starter
Burning Brakes
Joined: Apr 2005
Posts: 1,172
Likes: 0
From: Port Labelle Florida
Voltage Problem?
My 2005 Cpe with Auto Tran normally is showing 14.5v while driving with air on at regular and highway speeds...Has factory battery and 24K miles...At idle, it shows around 13...Never noticed it before until now...Is that the norm?
Safety Car
Joined: Feb 2007
Posts: 4,939
Likes: 448
From: CHOCOWINITY NC
If anything, 14.5 is too high which is why these cars go through batteries so fast.
From a previous post:
"A fresh battery will have a resting voltage of around 12.7V. (measured at 65 degrees after sitting with no draw for 12 hours). The only way to measure this accurrately is with a digital voltmeter AT the battery terminals. Just switching on your car will skew the numbers as you're throwing a bunch of power draws into the equation which will lower the V. readout. When an alternator is running it will put out between 13.5 and 14.1 volts into the battery depending on the batteries state of charge. This voltage is regulated by (duh!) a regulator. A batteries ability to hold and accept this charge has nothing really to do with how much you're trying to stuff into it. A fully charged batter will generally show an alternator supplied voltage of about 13.7 V depending on the voltage draw of the cars electrical systems. A battery with a low charge will typicallly show 14V or so as the battery capacity is replenished by the alternator output. A totally bad battery may not accept a charge at all. A higher charge rate will show at the first start of the day as the battery recovers lost voltage from sitting and parasitic draws as well as needing to recover from a high load engine start. Batteries naturally age and over a period of time their ability to hold a charge and full voltage diminishes. At 4 years or so this usually drops to about 50% of the original capacity. A bad or shorted cell can also cause failure as all cells need to be fairly consistant...
Test a battery by either:
1)Taking a resting voltage reading
2)doing a load test
Test an alternator by:
1)measuring voltage while running. Anything over the batteries resting voltage means it's putting out. Voltages less than 13 or so means it's not putting out enough..Sometimes a bad or shorted battery will not accept any voltage even when the alternator is good."
From a previous post:
"A fresh battery will have a resting voltage of around 12.7V. (measured at 65 degrees after sitting with no draw for 12 hours). The only way to measure this accurrately is with a digital voltmeter AT the battery terminals. Just switching on your car will skew the numbers as you're throwing a bunch of power draws into the equation which will lower the V. readout. When an alternator is running it will put out between 13.5 and 14.1 volts into the battery depending on the batteries state of charge. This voltage is regulated by (duh!) a regulator. A batteries ability to hold and accept this charge has nothing really to do with how much you're trying to stuff into it. A fully charged batter will generally show an alternator supplied voltage of about 13.7 V depending on the voltage draw of the cars electrical systems. A battery with a low charge will typicallly show 14V or so as the battery capacity is replenished by the alternator output. A totally bad battery may not accept a charge at all. A higher charge rate will show at the first start of the day as the battery recovers lost voltage from sitting and parasitic draws as well as needing to recover from a high load engine start. Batteries naturally age and over a period of time their ability to hold a charge and full voltage diminishes. At 4 years or so this usually drops to about 50% of the original capacity. A bad or shorted cell can also cause failure as all cells need to be fairly consistant...
Test a battery by either:
1)Taking a resting voltage reading
2)doing a load test
Test an alternator by:
1)measuring voltage while running. Anything over the batteries resting voltage means it's putting out. Voltages less than 13 or so means it's not putting out enough..Sometimes a bad or shorted battery will not accept any voltage even when the alternator is good."
Team Owner
Joined: Mar 2008
Posts: 21,502
Likes: 461
From: Southern Utah
13 at idle is OK if it goes up to 13.8 - 14.5 when you give it a little gas. 14.5 is the top of the acceptable range for a fully warmed up system. It will always be higher when the system is cold. Try 1200 rpm and see if it doesn't go up to 13.8....
Le Mans Master
Joined: Jan 2005
Posts: 5,611
Likes: 5
From: Thousand Oaks California
