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^^^^
It's GM Data from my 4 Volume 2014 C7 Service Manual. Note it is starting at 80% charge as the C7 like the C8 was also only charging to 80% to save energy. It also notes 50% is enough to start the car.
First look at the voltages from the Table:
80% is about 12.65 volts
50% is about 12.3 volts (They note 50% is sufficient to start the car.)
1 amp doesn't sound like much but for a parasitic drain it's ~12 Watts for 19.2 hours.
Using AndyBump's C8 parasitic drain test info, 0.015 amps X 12 volts = ~0.2 Watts (60 X less)
My Street Rod with no parasitic drain control circuits with some devices always powered (Digital Dash (maintains Odometer reading); Remote Door and Window Opener (waiting for a signal from the FOB); Remote Sound System Amp, CD Player (waiting for signal from their remotes to turn on) is ~40 milliamps = 0.04 amps X 12 volts = ~0.5 Watts. Still 12 Watts/0.5 Watts = 24 times less.
THE GM Logo'd CTEK made charger, like most CTEK chargers has a "Desulfation Mode." It might. Most trickle changers do not. But frankly even if it did it's life was shortened. After 3 months a new battery is best.
This is a great chart to show what is going on with the charging system and battery maintainer. If you watch the voltage display on the dash, you should notice the voltage cycles between 12.x volts to 14.x volts. I am not totally positive, but I think this is what's going on with the factory charging algorithm.
I'd like to share a story you may all find unbelievable or at least bewildering. At my Lexus dealership we had a retail
customer come in and purchase a battery over the counter. No big deal right? He calls us about an hour later very
upset because he thought we sold him a defective battery. (he didn't have the core with him at time of purchase btw)
We went through every possible scenario over the phone with him, we were certain that something else was wrong
with the installation. (often times people install the cables backwards and fry the fusible link rendering the car inoperable)
Anyways, the customer has the car towed in to our shop and to our " surprise, shock, heads shaking" the tech found the
problem in about 5 seconds. The customer had installed the battery and hooked up the cables with the protective plastic
caps still on the terminals. Tech fixed it in about a minute, fired it up and drove it out to the service drive. The customer was
a little embarrassed to say the least. I don't think he's ever been back. Hard to believe I know but true. Good info with many of
the posters here, just wanted to share an amusing anecdote regarding batteries.
.... I am not totally positive, but I think this is what's going on with the factory charging algorithm.
The factory charging system is being controlled by a computer to reduce energy use (like most modern cars.) It will only charge the battery to 80% and no more!
I have watched my voltage and it does just what the GM algorithm says it will do after the car has sat for a few days. On the 25/30 mile drive to town the dash Volt meter reads about 14 to 14.5 volts. That indicates it is powering all the cars needs, i.e radio etc AND charging the battery.
On the way home, usually early into the drive, there is a step drop to 13 to 13.5 volts. That indicates the battery is at 80% charge and the computer lowers the output to power the car accessories BUT not sufficient to charge the battery.
I NEVER park any of my cars in the garage without connecting the battery tender. In spite of that we've already had two batteries replaced under the warranty on our 2020 HTC.
When the battery dies, these cars are sealed bricks. Get familiar with the process to gain access to the car when the battery is dead!
For this ^^^^^ reason
the "dead battery" in a c8 worries me. Is there any consensus on how long an original c8 battery should last? And by long I'm not sure if time or miles are a better metric? I have a 23 HTC and will drive it about 5k miles per year.
the "dead battery" in a c8 worries me. Is there any consensus on how long an original c8 battery should last? And by long I'm not sure if time or miles are a better metric? I have a 23 HTC and will drive it about 5k miles per year.
First IF the battery dies you can access the Frunk with the mechanical key at the driver's door and pull a wire above the gas pedal and open the Frunk. Can jump start the car or in my case not bother and would install a new AGM battery. If concerned you might not be at home buy a Lithium battery jump starter. One in pic below found on Amazon for $59. They work.
My C8 is 3 years old, will start measuring battery voltage at~ 4 years and keep a record as it reduces. You must only check with a qualify VOM after over 12 hours when the car has not started. Otherwise your reading a surface change. At some point I'll decide, usually before winter that it's lime to reduce the risk and buy a new battery.
The voltage you are reading is charging system not battery voltage!
Correct. It is system voltage, which, if the engine is running will be higher than the battery voltage if the battery were not being actively charged or discharged. You can activate the car in the Service Mode by holding down the start button while NOT putting your foot on the brake. When it wakes up you can read that voltage. However, even that would not be exactly right - because with the system fired up but engine not running - the draw is already 10 amps or so even after the exterior lights are out. I know - I have measured it with clamp meter on the battery cable.
Here is a graphic representation of how the charging system works that I made from data in the Service Manual:
I had a weird thing happen on my 2021 HTC .... it would not let my CTEK charger past the first light. if I took charger off voltage would slowly drop. so I had dealer look and see if battery was going bad. here to find out my car was trying to update the radio, which I was declining. dealer told me radio would not shut off due to the car trying to do a update that's why everything was going on. so they updated car and and charger and battery are working fine !
I had a weird thing happen on my 2021 HTC .... it would not let my CTEK charger past the first light. if I took charger off voltage would slowly drop. so I had dealer look and see if battery was going bad. here to find out my car was trying to update the radio, which I was declining. dealer told me radio would not shut off due to the car trying to do a update that's why everything was going on. so they updated car and and charger and battery are working fine !
Yep, that is what it does if an undate is needed. It keeps tha radio playing to tell you an update is needed.
‘’After 3 years I know the signal! Funny it would not allow the charger to get past the first light.
I've also started to carry a lithium battery jump starter in the frunk. Just in case I'm nowhere near home and the battery loses its charge. I normally keep the C8 connected to a CTEK charger/maintainer when it's not being driven.
In Texas batteries only last 2-3 years becuase of the heat. My wife's Traverse stopped doing aoutstart while everything else worked. We got the batttery tested and it was bad, again, even though the car would start and run just fine. After replacing the battery the autostart worked again (I know autostart sucks). Point is, they can begin to get weak and can cause flaky electrical problems. Pays to have them tested every couple years.
In Texas batteries only last 2-3 years becuase of the heat. My wife's Traverse stopped doing aoutstart while everything else worked. We got the batttery tested and it was bad, again, even though the car would start and run just fine. After replacing the battery the autostart worked again (I know autostart sucks). Point is, they can begin to get weak and can cause flaky electrical problems. Pays to have them tested every couple years.
I've had a lot better luck than that in the Phoenix heat, but I was religious about my cars on maintainers when they were sitting idle in garages.
Discovered today I have a dead battery. Had to use the hatch and key and pull the door cord to get in (thank god I’ve paid attention)…battery is out and charging. Won’t get past stage/test 6 (?)… battery appears to be the original (17 GS) it says GM on it.
would it just fail like that with no advance warning? What could I have done to cause it to drain? Anything? I’m new to vetted so I don’t know what I don’t know.
It does sit for several days at a time. This time hasn’t been moved since Saturday.
What kind of issues can I expect once a good battery is installed?
Discovered today I have a dead battery. Had to use the hatch and key and pull the door cord to get in (thank god I’ve paid attention)…battery is out and charging. Won’t get past stage/test 6 (?)… battery appears to be the original (17 GS) it says GM on it.
would it just fail like that with no advance warning? What could I have done to cause it to drain? Anything? I’m new to vetted so I don’t know what I don’t know.
It does sit for several days at a time. This time hasn’t been moved since Saturday.
What kind of issues can I expect once a good battery is installed?
thanks for any help. 🤗
7 year old battery? Any battery over 4 years old is on borrowed time.
Discovered today I have a dead battery. Had to use the hatch and key and pull the door cord to get in (thank god I’ve paid attention)…battery is out and charging. Won’t get past stage/test 6 (?)… battery appears to be the original (17 GS) it says GM on it.
would it just fail like that with no advance warning? What could I have done to cause it to drain? Anything? I’m new to vetted so I don’t know what I don’t know.
It does sit for several days at a time. This time hasn’t been moved since Saturday.
What kind of issues can I expect once a good battery is installed?
thanks for any help. 🤗
Well, to start with, this is a C8 forum. But the C7 and C8 charging systems and battery draws are similar.
You're talking about a 6 year old OEM battery and, yes, batteries can fail like that.
If you often go more than a week without starting your car then a battery maintainer is a good idea.
If you install a good battery then you shouldn't expect any more issues other than perhaps re-indexing the windows and some memory setting losses once you put the new battery in.
Well, to start with, this is a C8 forum. But the C7 and C8 charging systems and battery draws are similar.
You're talking about a 6 year old OEM battery and, yes, batteries can fail like that.
If you often go more than a week without starting your car then a battery maintainer is a good idea.
If you install a good battery then you shouldn't expect any more issues other than perhaps re-indexing the windows and some memory setting losses once you put the new battery in.
Sorry about the wrong model post/comment/questions. I did a forum search ….
Thank you for the response/information.
I’ll wander on back to my side of the tracks ☺️
True. Replacing it tomorrow. Thank you for the reply.
This is more than you may want to know about batteries but discusses how I check voltage and will start soon for my 3-year-old C8. My early 2014 C7 probably had a weak cell when new. At 3 years, just before winter, I replaced with an AMG (Absorbed Glass Mat) Diehard in that case, because of a low voltage reading. Had my 2017 Grand Sport 4 years AND if I wasn't getting an early C8 might have replaced, again before winter.
