What does your volt gage read (gage on far left of cluster)???
08-29-2009, 11:56 PM
#17
Drifting
A quick check, rule of thumb, is that without the engine running and minimum load on the battery it should read above 12 volts. Start the engine, idle, and the meter should go well above 12 volts. Now turn on both your high and low beams and the voltage should drop slightly but not fully back to the engine not running voltage.
08-30-2009, 09:31 AM
#18
Drifting
Voltages while driving are not related to the battery, but to the alternator, and should be mid-14s to start, and mid-13s while driving any length of time. If voltage is in the 12V range (or less) while driving, the alternator has failed and is not doing its job.
First thing I'd do is check to ensure gauge calibration (not to mention eyeball interpolation; 9:30 isn't a voltage measurement!) by using a multimeter to check this voltage at the battery terminals with a multimeter while the car is running- check the battery before and right after start, and again before you turn the car off after driving it.
This is all related to charging on a 12V system, and extending battery life. 14V is fine for the battery for short durations. 15-16V is overcharging it and would rather quickly drive off water and harm the cells.
As the car sits, the battery is constantly in-use for the security system, the keyless entry, running the radio clock, etc. Not a whole lot, but it all can add up. Whenever you start the car, the starter consumes a really big chunk of electricity from the battery. The battery will continue to have usable energy until it drops below 10V in which case don't even bother trying to recharge it, just go get a new one.
When you start the car, the alternator ramps up to a fast-charge of about 14.5V for a short period to recharge this as quickly as possible. If the alternator maintained this voltage all the time, it would overcharge and decrease battery life, so the alternator will ramp down after a few minutes to about 13.5V float charge (or trickle charge) level, which is a safe voltage to always keep the batteries at while charging. Same is true of plug-in battery chargers/battery maintainers.
When you stop the car, the batteries will slowly creep back down to their natural voltage of somewhere around 12.0-12.8V, depending on age/condition. At voltages under 12.5V, sulfation can form, which hurts the battery and reduces cranking amps. It's a slow growth that occurs over time. It largely all dissolves when a higher float voltage is applied to recharge it, but sulfation is an insulator, and if it grows large enough, it can completely choke off a cell and result in a dead battery. A good new battery with a full charge has a shelf life of about 6 months before irreparable harm is done; older batteries... not so long. My battery right now is sitting at 12.15V, which is awfully low. So long as I continue to drive it regularly to drive off the sulfation, it will keep starting the car, but if I'd let the car sit for a month, I have no doubt it'd be dead. I know I should replace it before it locks me out of the frunk, but I keep procrastinating.
The surface of the electrodes in a car battery are a very complex waffle sort of pattern, designed to maximize surface area, and give maximum cold cranking amps, but is rather fragile. Every time you deep cycle the battery, you damage these structures a little. Too many, and you can just throw the battery away. Deep cycle marine batteries and UPS batteries use a different electrode design, a more simple one that's thicker and gives less cranking amps, but longer life; these can last for hundreds of deep cycles.
First thing I'd do is check to ensure gauge calibration (not to mention eyeball interpolation; 9:30 isn't a voltage measurement!) by using a multimeter to check this voltage at the battery terminals with a multimeter while the car is running- check the battery before and right after start, and again before you turn the car off after driving it.
As the car sits, the battery is constantly in-use for the security system, the keyless entry, running the radio clock, etc. Not a whole lot, but it all can add up. Whenever you start the car, the starter consumes a really big chunk of electricity from the battery. The battery will continue to have usable energy until it drops below 10V in which case don't even bother trying to recharge it, just go get a new one.
When you start the car, the alternator ramps up to a fast-charge of about 14.5V for a short period to recharge this as quickly as possible. If the alternator maintained this voltage all the time, it would overcharge and decrease battery life, so the alternator will ramp down after a few minutes to about 13.5V float charge (or trickle charge) level, which is a safe voltage to always keep the batteries at while charging. Same is true of plug-in battery chargers/battery maintainers.
When you stop the car, the batteries will slowly creep back down to their natural voltage of somewhere around 12.0-12.8V, depending on age/condition. At voltages under 12.5V, sulfation can form, which hurts the battery and reduces cranking amps. It's a slow growth that occurs over time. It largely all dissolves when a higher float voltage is applied to recharge it, but sulfation is an insulator, and if it grows large enough, it can completely choke off a cell and result in a dead battery. A good new battery with a full charge has a shelf life of about 6 months before irreparable harm is done; older batteries... not so long. My battery right now is sitting at 12.15V, which is awfully low. So long as I continue to drive it regularly to drive off the sulfation, it will keep starting the car, but if I'd let the car sit for a month, I have no doubt it'd be dead. I know I should replace it before it locks me out of the frunk, but I keep procrastinating.
The surface of the electrodes in a car battery are a very complex waffle sort of pattern, designed to maximize surface area, and give maximum cold cranking amps, but is rather fragile. Every time you deep cycle the battery, you damage these structures a little. Too many, and you can just throw the battery away. Deep cycle marine batteries and UPS batteries use a different electrode design, a more simple one that's thicker and gives less cranking amps, but longer life; these can last for hundreds of deep cycles.
Last edited by sjfehr; 08-30-2009 at 10:01 AM.
08-30-2009, 04:12 PM
#20
Drifting
Thread Starter
Google works great doesn't it
Voltages while driving are not related to the battery, but to the alternator, and should be mid-14s to start, and mid-13s while driving any length of time. If voltage is in the 12V range (or less) while driving, the alternator has failed and is not doing its job.
First thing I'd do is check to ensure gauge calibration (not to mention eyeball interpolation; 9:30 isn't a voltage measurement!) by using a multimeter to check this voltage at the battery terminals with a multimeter while the car is running- check the battery before and right after start, and again before you turn the car off after driving it.
This is all related to charging on a 12V system, and extending battery life. 14V is fine for the battery for short durations. 15-16V is overcharging it and would rather quickly drive off water and harm the cells.
As the car sits, the battery is constantly in-use for the security system, the keyless entry, running the radio clock, etc. Not a whole lot, but it all can add up. Whenever you start the car, the starter consumes a really big chunk of electricity from the battery. The battery will continue to have usable energy until it drops below 10V in which case don't even bother trying to recharge it, just go get a new one.
When you start the car, the alternator ramps up to a fast-charge of about 14.5V for a short period to recharge this as quickly as possible. If the alternator maintained this voltage all the time, it would overcharge and decrease battery life, so the alternator will ramp down after a few minutes to about 13.5V float charge (or trickle charge) level, which is a safe voltage to always keep the batteries at while charging. Same is true of plug-in battery chargers/battery maintainers.
When you stop the car, the batteries will slowly creep back down to their natural voltage of somewhere around 12.0-12.8V, depending on age/condition. At voltages under 12.5V, sulfation can form, which hurts the battery and reduces cranking amps. It's a slow growth that occurs over time. It largely all dissolves when a higher float voltage is applied to recharge it, but sulfation is an insulator, and if it grows large enough, it can completely choke off a cell and result in a dead battery. A good new battery with a full charge has a shelf life of about 6 months before irreparable harm is done; older batteries... not so long. My battery right now is sitting at 12.15V, which is awfully low. So long as I continue to drive it regularly to drive off the sulfation, it will keep starting the car, but if I'd let the car sit for a month, I have no doubt it'd be dead. I know I should replace it before it locks me out of the frunk, but I keep procrastinating.
The surface of the electrodes in a car battery are a very complex waffle sort of pattern, designed to maximize surface area, and give maximum cold cranking amps, but is rather fragile. Every time you deep cycle the battery, you damage these structures a little. Too many, and you can just throw the battery away. Deep cycle marine batteries and UPS batteries use a different electrode design, a more simple one that's thicker and gives less cranking amps, but longer life; these can last for hundreds of deep cycles.
First thing I'd do is check to ensure gauge calibration (not to mention eyeball interpolation; 9:30 isn't a voltage measurement!) by using a multimeter to check this voltage at the battery terminals with a multimeter while the car is running- check the battery before and right after start, and again before you turn the car off after driving it.
This is all related to charging on a 12V system, and extending battery life. 14V is fine for the battery for short durations. 15-16V is overcharging it and would rather quickly drive off water and harm the cells.
As the car sits, the battery is constantly in-use for the security system, the keyless entry, running the radio clock, etc. Not a whole lot, but it all can add up. Whenever you start the car, the starter consumes a really big chunk of electricity from the battery. The battery will continue to have usable energy until it drops below 10V in which case don't even bother trying to recharge it, just go get a new one.
When you start the car, the alternator ramps up to a fast-charge of about 14.5V for a short period to recharge this as quickly as possible. If the alternator maintained this voltage all the time, it would overcharge and decrease battery life, so the alternator will ramp down after a few minutes to about 13.5V float charge (or trickle charge) level, which is a safe voltage to always keep the batteries at while charging. Same is true of plug-in battery chargers/battery maintainers.
When you stop the car, the batteries will slowly creep back down to their natural voltage of somewhere around 12.0-12.8V, depending on age/condition. At voltages under 12.5V, sulfation can form, which hurts the battery and reduces cranking amps. It's a slow growth that occurs over time. It largely all dissolves when a higher float voltage is applied to recharge it, but sulfation is an insulator, and if it grows large enough, it can completely choke off a cell and result in a dead battery. A good new battery with a full charge has a shelf life of about 6 months before irreparable harm is done; older batteries... not so long. My battery right now is sitting at 12.15V, which is awfully low. So long as I continue to drive it regularly to drive off the sulfation, it will keep starting the car, but if I'd let the car sit for a month, I have no doubt it'd be dead. I know I should replace it before it locks me out of the frunk, but I keep procrastinating.
The surface of the electrodes in a car battery are a very complex waffle sort of pattern, designed to maximize surface area, and give maximum cold cranking amps, but is rather fragile. Every time you deep cycle the battery, you damage these structures a little. Too many, and you can just throw the battery away. Deep cycle marine batteries and UPS batteries use a different electrode design, a more simple one that's thicker and gives less cranking amps, but longer life; these can last for hundreds of deep cycles.
08-30-2009, 04:48 PM
#21
Drifting
That was all off the top of my head, actually, I'm an EE and work a lot with batteries in industrial applications and thought I'd share some detail with ya'll. Batteries are often misunderstood and mistreated. Speaking of which, heat is a real killer- for the cheap sealed VRLA batteries everyone uses these days, every 15F over 77F will cut the life in half. At least Porsche put the battery in a cool location for a change, most cars throw them right in the hottest part of the car, which always struck me as incredible stupid. Especially when it *could* go in the trunk and improve weight distribution, too.
