Be grateful for GM engineering
Safety Car
Joined: Apr 2007
Posts: 4,548
Likes: 609
From: Southeast, WI
Racer
Joined: Aug 2014
Posts: 368
Likes: 164
On the subject of batteries, I have a nine-year-old Prius, with 185,000+ miles, and not only have I not replaced the traction high voltage battery, I have never replaced the small 12 volt battery "starter" battery either, even though I have accidentally discharged it twice! Strange! 
Melting Slicks
Joined: Dec 2009
Posts: 2,749
Likes: 50
From: Westmont Il.
So better add Japan, China, the EU countries and soon...North Korea. Of all those I just listed, all except North Korea launch their own satellites and could send a human to the moon if they wanted to. North Korea coming soon except you know what they want to put on top of their launch vehicles...
Burning Brakes
Joined: May 2007
Posts: 1,171
Likes: 4
From: Columbia Maryland
The "average" new car has a battery warranty rate of just under 50% (meaning that just under 50% of batteries die within 3 years). Some car lines (Jeep Grand Cherokees were bad for a while) have a 70% warranty rate.
The reason isn't poor engineering, the reason is WE HAVE TOO MUCH ELECTRICAL STUFF IN THE CAR!
It's a 12V battery with LIMITED AMP support. Cold cranking amps are only for the start, once running the amperage drops a lot. Add to that your car basically needs your alternator to power the system (it raises the cars voltage to 14.7 or sometimes 15.3 volts to lower amperage draw!) The alternator also puts parasitic drain on the engine so "intelligent" power management systems (which all new cars have) attempt to use the alternator only when the BATTERY can't support the 14.7 volts!
How do they do all this, overcharging the battery during use, mind you again that your battery is being pummeled by the car, and it is slow to react, the alternator doesn't just charge the battery it tries to handle dynamic transient loads (like when you make a quick maneuver with your electric steering and you draw 60-100 amps from the system for 500 ms).
I could go on all day about batteries, alternators, amp usage, and the like in cars. But one thing needs to be said, until we move to a 42 volt (36 + 6 volt margin) or a true 48 volt system we are going to have significant issues in this regard.
You know what type of car doesn't have battery issues.... A HYBRID. That's it, everyone else is boned.
The reason isn't poor engineering, the reason is WE HAVE TOO MUCH ELECTRICAL STUFF IN THE CAR!
It's a 12V battery with LIMITED AMP support. Cold cranking amps are only for the start, once running the amperage drops a lot. Add to that your car basically needs your alternator to power the system (it raises the cars voltage to 14.7 or sometimes 15.3 volts to lower amperage draw!) The alternator also puts parasitic drain on the engine so "intelligent" power management systems (which all new cars have) attempt to use the alternator only when the BATTERY can't support the 14.7 volts!
How do they do all this, overcharging the battery during use, mind you again that your battery is being pummeled by the car, and it is slow to react, the alternator doesn't just charge the battery it tries to handle dynamic transient loads (like when you make a quick maneuver with your electric steering and you draw 60-100 amps from the system for 500 ms).
I could go on all day about batteries, alternators, amp usage, and the like in cars. But one thing needs to be said, until we move to a 42 volt (36 + 6 volt margin) or a true 48 volt system we are going to have significant issues in this regard.
You know what type of car doesn't have battery issues.... A HYBRID. That's it, everyone else is boned.
Car batteries aren't failing more often because of the load when the car is running, but because there is a load when they AREN'T running.
Things like keyless entry systems, alarms, OnStar, etc. run all the time which causes the battery to slowly discharge. When a lead-acid battery isn't fully charged it suffers from battery sulfation which is a chemical reaction which eventually requires the battery to be replaced. Between the current draw when the car isn't running and that the car must be running longer to charge it back to full capacity means that the battery sufation occurs for much longer periods which leads to shorter life. The deeper the discharge the faster (exponentially) sulfation occurs which is why a deep discharge of a regular car battery can kill it. (Deep-cycle batteries have slightly different lead-acid chemistry which reduces sulfation when deeply discharged but also reduces the how fast the battery can discharge power (it's CCA rating).)
Before all the electronics in cars, when you parked your car the battery was FULLY charged and didn't suffer battery sulfation as quickly because it remained fully charged. Period.
Hybrids use Nickel-Metal-Hydride or Lithium-Ion batteries which are much more expensive and have different battery characteristics than lead-acid batteries.
Le Mans Master
Joined: Oct 2005
Posts: 7,002
Likes: 2,679
Obviously you failed getting your Electrical Engineering degree because your explanation of how a car's electrical system (or any DC power system) works is completely wrong and your analysis of car battery failure is also completely wrong.
Car batteries aren't failing more often because of the load when the car is running, but because there is a load when they AREN'T running.
Things like keyless entry systems, alarms, OnStar, etc. run all the time which causes the battery to slowly discharge. When a lead-acid battery isn't fully charged it suffers from battery sulfation which is a chemical reaction which eventually requires the battery to be replaced. Between the current draw when the car isn't running and that the car must be running longer to charge it back to full capacity means that the battery sufation occurs for much longer periods which leads to shorter life. The deeper the discharge the faster (exponentially) sulfation occurs which is why a deep discharge of a regular car battery can kill it. (Deep-cycle batteries have slightly different lead-acid chemistry which reduces sulfation when deeply discharged but also reduces the how fast the battery can discharge power (it's CCA rating).)
Before all the electronics in cars, when you parked your car the battery was FULLY charged and didn't suffer battery sulfation as quickly because it remained fully charged. Period.
Hybrids use Nickel-Metal-Hydride or Lithium-Ion batteries which are much more expensive and have different battery characteristics than lead-acid batteries.
Car batteries aren't failing more often because of the load when the car is running, but because there is a load when they AREN'T running.
Things like keyless entry systems, alarms, OnStar, etc. run all the time which causes the battery to slowly discharge. When a lead-acid battery isn't fully charged it suffers from battery sulfation which is a chemical reaction which eventually requires the battery to be replaced. Between the current draw when the car isn't running and that the car must be running longer to charge it back to full capacity means that the battery sufation occurs for much longer periods which leads to shorter life. The deeper the discharge the faster (exponentially) sulfation occurs which is why a deep discharge of a regular car battery can kill it. (Deep-cycle batteries have slightly different lead-acid chemistry which reduces sulfation when deeply discharged but also reduces the how fast the battery can discharge power (it's CCA rating).)
Before all the electronics in cars, when you parked your car the battery was FULLY charged and didn't suffer battery sulfation as quickly because it remained fully charged. Period.
Hybrids use Nickel-Metal-Hydride or Lithium-Ion batteries which are much more expensive and have different battery characteristics than lead-acid batteries.
You can't sufficiently charge a battery when the car is on, to have it survive the drain when it's off.
Seriously, you don't have to believe me, but this is how cut throat it is on the battery side. We have undersized alternators and "intelligent" charging systems to loading the engine due to fuel economy.
At some point we just need to put more power into the car.
And actually I didn't fail anything in EE I just don't have time to write an entire backstory on the existence of things, and I assume the average person can connect the dots. But thanks for explaining the more boring stuff so I don't have to.
Also my point with hybrids wasn't related to battery chemistry, but rather storage capacity. They have more capacity than a regular 12V system (and via a DC/DC converter they keep the 12V side and lead acid battery better charged).
Last edited by user051728; May 26, 2015 at 07:38 AM.
Le Mans Master
Joined: Oct 2005
Posts: 7,002
Likes: 2,679
Actually I'm not. Airbags historically have been connected to "ignition hot" circuits and not "always hot" circuits. This has started to change, and I think in the next 5 years will become the obsolete method. But that doesn't change the fact that pretty much all cars from 1985 (or whenever the first airbag was launched) until 2010 (or later) have this type of setup.
Instructor
Joined: May 2015
Posts: 115
Likes: 2
From: houston tx
u are wrong more !!!!!
Actually I'm not. Airbags historically have been connected to "ignition hot" circuits and not "always hot" circuits. This has started to change, and I think in the next 5 years will become the obsolete method. But that doesn't change the fact that pretty much all cars from 1985 (or whenever the first airbag was launched) until 2010 (or later) have this type of setup.
standard 7 series BMW 2011 and up equipped with 2 batteries and 1 of em is over 1000 cold cranking amps.....
it is not the running time that drain battery.Most computer wont turn off when the key is off because module like EVap sys now are design to run the monitor when the key is off
Also GM keys came outta the ignition is not becuz of design...Nissan,toyota and others too....it is because people put tooo many keys together in the key chain ,dangling on ignition sw. and wore out the sw......I know it cuz I've seen too many times in and outta the shop.....the government pick on GM because they are easier just like the saddle tank on the pu' last time
Le Mans Master
Joined: Oct 2005
Posts: 7,002
Likes: 2,679
standard 7 series BMW 2011 and up equipped with 2 batteries and 1 of em is over 1000 cold cranking amps.....
it is not the running time that drain battery.Most computer wont turn off when the key is off because module like EVap sys now are design to run the monitor when the key is off
Also GM keys came outta the ignition is not becuz of design...Nissan,toyota and others too....it is because people put tooo many keys together in the key chain ,dangling on ignition sw. and wore out the sw......I know it cuz I've seen too many times in and outta the shop.....the government pick on GM because they are easier just like the saddle tank on the pu' last time
it is not the running time that drain battery.Most computer wont turn off when the key is off because module like EVap sys now are design to run the monitor when the key is off
Also GM keys came outta the ignition is not becuz of design...Nissan,toyota and others too....it is because people put tooo many keys together in the key chain ,dangling on ignition sw. and wore out the sw......I know it cuz I've seen too many times in and outta the shop.....the government pick on GM because they are easier just like the saddle tank on the pu' last time
I agree the key problem is one of "unintended" usage of having a bazillion keys on a key ring. However even without the ignition issue, a person could turn off a key and disable their own airbags. However I'm sure most people didn't know that, they assume vehicle is moving therefore my airbag (and power steering, and other things) should be working, when this was not the case (or the design intent).
Unfortunately in todays day and age we have to engineer to the lowest common denominator. I have to assume people will do things like turn off the ignition while driving, or take their hands off the wheel.
Instructor
Joined: May 2015
Posts: 115
Likes: 2
From: houston tx
fixing...
Everything is either off or in sleep mode when the key is off. A lot of modules are in sleep mode (with a drain current) but the airbag hasn't historically been one of those modules. They powered down the circuits to make them "safe" for service.
I agree the key problem is one of "unintended" usage of having a bazillion keys on a key ring. However even without the ignition issue, a person could turn off a key and disable their own airbags. However I'm sure most people didn't know that, they assume vehicle is moving therefore my airbag (and power steering, and other things) should be working, when this was not the case (or the design intent).
Unfortunately in todays day and age we have to engineer to the lowest common denominator. I have to assume people will do things like turn off the ignition while driving, or take their hands off the wheel.
I agree the key problem is one of "unintended" usage of having a bazillion keys on a key ring. However even without the ignition issue, a person could turn off a key and disable their own airbags. However I'm sure most people didn't know that, they assume vehicle is moving therefore my airbag (and power steering, and other things) should be working, when this was not the case (or the design intent).
Unfortunately in todays day and age we have to engineer to the lowest common denominator. I have to assume people will do things like turn off the ignition while driving, or take their hands off the wheel.
of course when u look at the foreign design ..its already push button sw. ....such as the C6 vette
Instructor
Joined: Jul 2004
Posts: 121
Likes: 4
From: Atlanta Georgia
My personal experience with batteries has been good. I always start them out with a good charge state by connecting to a CTEK charger. Many vehicles start out with a low-charge state after sitting in transport and dealer inventory and never get up to "snuff" until a fair amount of driving. It's always been my belief that a good initial charge state is important. Having said that, I always replace batteries at 5 years max and tires the same irrespective of miles. If my Corvette would be sitting for more than 3 or 4 days I would usually plug in the CTEK. I did a hard-mount so it was easy to do.
Burning Brakes
Joined: Oct 2012
Posts: 933
Likes: 3
From: Dallas, TX
You go with Germany if you want luxury with more sportiness and are willing to sacrifice some reliability and cheap maintenance.
... Although I think Lexus has been making some pretty fun cars lately, too. At least as fun as a luxury car with a slushbox can be.
Melting Slicks
Joined: Jun 2008
Posts: 2,168
Likes: 50
From: Somerville New Jersey
Le Mans Master
Joined: Oct 2005
Posts: 7,002
Likes: 2,679
Actually not......most of the manufactures on last 3 yrs production already done and expire ignition...the key is only merely establish an identification verification for immobilizer so it will wake up the ECU and hand shake with other modules for the startup ..a 2010 avenger from Chrysler already have no ignition sw......ign sw is a bad idea anyway .....cuz it pwr up almost anything and too much current running thru acting like a dist center ....that should be the jobs of multiple relay to divide and deliver power but not on 1 central on and off sw.
of course when u look at the foreign design ..its already push button sw. ....such as the C6 vette
of course when u look at the foreign design ..its already push button sw. ....such as the C6 vette
C6 and C7 Vette work the same way, the fact you have a button doesn't remove ignition states from the logic equation. They in fact still exist.
Melting Slicks
Joined: Sep 2009
Posts: 2,414
Likes: 214
From: Sarasota Florida
My C6 battery lasted five years in Florida where the heat really affects battery life. Of course, my C6 was a daily driver. I suspect that is a factor.
Burning Brakes
Joined: Apr 2015
Posts: 753
Likes: 166
From: Buffalo Minnesota
Battery not fully charged after driving.
One thing I've noticed since this discussion started is that the battery on my C7 doesn't seem to be fully charged, even after a drive of more than an hour. I recently hardwired a connection for my battery tender to the battery to make it easy to plug in and started using the battery tender any time I'm not going to drive the car for a couple of days.
When first plugged in, the battery tender goes through three modes. First the light is red, indicating charging. When it hits 85% the red light stays on but the green light is flashing. When its fully charged, it goes into maintenance mode whit the red light off and the green light on steady. It will cycle through all three modes even if the battery is fully charged...in which case it would all happen quickly.
This is the same unit I was using on my C5 up until April when I traded it in. On the C5, if I came back from a drive and plugged in the tender, it would cycle through to maintenance mode pretty quickly.
On the C7, same scenario, I came back 24 hours later and it was still flashing green meaning it still had not made it to full charge. It took several more hours to get to maintenance mode. Granted its only .75 amps but I would have expected that after driving the battery would already be fully charged. The length of time its taking to get to maintenance mode seems to be telling me that it is really somewhere above 85% but less than full charge.
Just an observation. I'm not claiming to know why this is. But given that its not really fully charged just from driving it, my strategy of putting the tender on it when its going to sit for a couple of days seems reasonable.
When first plugged in, the battery tender goes through three modes. First the light is red, indicating charging. When it hits 85% the red light stays on but the green light is flashing. When its fully charged, it goes into maintenance mode whit the red light off and the green light on steady. It will cycle through all three modes even if the battery is fully charged...in which case it would all happen quickly.
This is the same unit I was using on my C5 up until April when I traded it in. On the C5, if I came back from a drive and plugged in the tender, it would cycle through to maintenance mode pretty quickly.
On the C7, same scenario, I came back 24 hours later and it was still flashing green meaning it still had not made it to full charge. It took several more hours to get to maintenance mode. Granted its only .75 amps but I would have expected that after driving the battery would already be fully charged. The length of time its taking to get to maintenance mode seems to be telling me that it is really somewhere above 85% but less than full charge.
Just an observation. I'm not claiming to know why this is. But given that its not really fully charged just from driving it, my strategy of putting the tender on it when its going to sit for a couple of days seems reasonable.