a C8 that is healthy with no parasitic draw or charging issues Should last you at least three weeks without a battery tender just sitting, locked up and parked.

 

This is not my experience. My C6 needed two replacement batteries over 8 years and 87,000 miles. In fact, the car sat at the dealer for 7 weeks waiting for a steering gear and yet it started right up when the part was to be installed. My C8 is over 3-1/2 years old with 44,000 miles and still on the original battery.

 

I'm new to Corvettes but decided to jump in after trading in my C63S AMG and I'm so disappointed! My biggest issue, that just rose up, is battery drain. I just got my car back from the dealer for service (oil change and alignment) and the next morning my battery was dead. I charged it and put it back in and the car started right up and I noticed the alternator voltage was 14.4v but after driving for a few minutes it dropped down to 12.6v but would spike occasionally. The battery drained down to 9.9v and would not crank. This happened 3 or 4 times but the battery checked out "good". I purchased a new battery and am seeing signs of potentially the same issue. When I start the car the voltage shows 14.4v but after a minute or so of driving it drops to 12.5 - 12.6v and sometimes spikes to 14.7v then back to 12.6v. I swung by the dealer and one guy at the service desk said this is normal. I don't believe or for one second. I need to get rid of this thing.

 

Yeah, somethings drawing power. One flukey, bad battery is one thing, but if the issue is persisting, you have something drawing power, or you're not charging properly.

 

It is normal to only see 12.6 volts after driving for awhile.
Apparently it is to save gas,

It will spike up when you turn on a load, and then drop down after awhile.

 

If I understand you correctly the battery replacement fixed the problem but you are concerned about what the voltage regulator is doing. I suspect that the service guy is correct but will humbly wait for others to chime in.

 

2020 here on original battery. Getting nervous.

 

that's what I've been hearing as well but one day the alternator voltage will stay at 14.1-14.7v then the next morning it'll be 14+v for a few minutes then go straight to 12.6v. That is so weird to me.

 

many cars these days have what they call intelligent charging, that means that the alternator will vary the voltage depending on the demand and battery condition. A Corvette does not need a tender to be part of its normal regimen. You only need to use a tender if you’re letting the car sit for weeks and Bmw has had that situation for a years. I can go as long as three weeks on my car and never have a problem starting it. There is something wrong with a car that basically needs a tender 24 seven.

 

You need to read how these charging systems work. What the tech told you is correct and that is the way the system works. The primary function is to keep all of the car electronics in the voltage range required. It's secondary function is to charge the battery. A 30 mile drive won't do much for charging the battery . You need to find a way to keep it on the charger but 1st remove it and get it charged and load tested. A fully charged battery should last 2 weeks or more if used every day. I have a 2020 with 47K miles on it and the orig. battery. Goes on maintainer if I don't use it for a week but that is pretty rare. OK 40* here so heading for the car wash. Enjoy the ride.

 

It is normal. Your battery is not discharging any more right? Now you are just concerned about the voltage. The charging system estimates the state of charge of the battery by measuring resting voltage when the car has been off for 4 or more hours, and then when it is running it keeps a continuous estimate of the state of charge by measuring current into and out of the battery. Then based on that SOC and other factors it selects a charging mode. Each charging mode has a different voltage range. This info is explained in the Service Manual that your technician uses. Here is a summary from the manual: "As the charging systems works to maintain the battery charge and manage vehicle electrical loads, it is normal for the voltmeter gauge on the instrument cluster or the system voltage displayed in the DIC to fluctuate or change. This does not indicate a malfunction. Depending on the battery state of charge and the vehicle electrical load, these values may be anywhere from 12.5V to 15.5V."

Honestly, I don't know why GM includes a voltage info tile. The manual give no information about how to interpret it. It seems to create mostly confusion. I never look at mine except when it comes up in threads. When the engine is running, the voltage you see is the system voltage or charging voltage. You cannot see (ever) the battery resting voltage using the DIC display. This is because even if you turn the engine off, you must put the car in the service mode to read the voltage. And, when in service mode, the car is drawing on the order of 10 amps (I measured that).

I made a graphic depiction of the charging modes using data from the Service Manual. Here it is.

 

OP do you have anything plugged into the ODB port?

 

Its normal behavior for the charging system as noted above. But are you have starting issues after replacement of the battery? And how did you read the 9.9 volts? You didn't see that while the engine was running did you? Parasitic draw after the car has sat off and undisturbed for a few minutes is about 10-15 ma. I measured it. But if you have a Lojack, or some dealer installed tracking device, for example, that will increase the parasitic draw. There have also been (infrequent) reports of an actual issue that caused parasitic draw. You can measure it if you want. This thread explains how I did it.

https://www.corvetteforum.com/forums...e-battery.html

 

I had the exact same issue with my C7 which I bought used from Arrowhead Cadillac. I finally took the car back to them after the third battery was replaced in a month. The car was purchased from Hertz by Arrowhead. They found a gps tracking device that was on all the time and it was draining the battery. They removed it and the problem ended.

 

Window sticker notes battery protection package ? $100.00 any one can explain what this add on is ? worth it ?

 

Its a CTEK battery charger/maintainer (the manual that comes with it calls it a charger) with a C8 logo. And a cigarette style plug that fits right into the outlet in the frunk for charging. Its worth it to me. You can by a similar CTEK version for a little less but it will not include the plug - you have to obtain that separately.

The Corvette version also indicates in the manual that came with the charger that it is compatible with FLA, AGM, and Lithium batteries, and it is the same one supplied with the Eray that has a 12v lithium starting battery. Some of the other CTEK versions do not indicated compatibility with Lithium.

My 2021 is on the maintainer whenever its parked in my garage. Still has the original battery.

 

Hmm, you are mostly right BUT your 30 miles is "not enough" is close but it can fully charge in about that driving distance. Also in my two C7s (a 2014 and 2017) and now two C8s, a 2020 and now 2024 E-Ray hardly even use my CTEK charger. The latest for my E-Ray is GM's CTEK supplied combo Li-Ion/Lead acid battery charger.

I monitored battery charging in my C8 often as have battery voltage on my dash meter. My Vettes are DDs BUT been retired since 2000 and do not need to drive every day. If my car sat for say 4 days, on the ~30 mile trip to town the battery voltage would be at ~14 volts. The days of a mechanical voltage regulator are long gone. Battery voltage (actually you are reading Alternator voltage on a dash meter) is controlled like everything else in the car my a microchip! GM says they only charge the battery to 80% as they call a fuel economy level to save energy. So the 14 to 14.5 volts is supplying all electrical power AND charging the battery to that 80%. On my way home from town, soon after I started there was a step change in the meter voltage to ~ 13 to 13.5 volts. That meant the battery was at 80% charge and their charging algorithms reduced the Alternator voltage to just enough to run whatever was operating electrically, fans, sound system, etc BUT not enough to further charge the battery. (That is all day time driving and no rain. If at night, wipers are going, speeds exceed a certain level the GM algorithms charge differently.)

As far as plugging into a maintenance charger, I very seldom do. Was on vacation for 3 weeks on both C7s and C8s never used my charger! No need, cars started just fine. in fact for the C8 @Andybump measured a parasitic current draw of ONLY ~10 milliamps after 10 minutes. Yep the C7 and C8 has circuits that shut all significant power down after ~10 minutes. Want to test? Open Frunk and Truck wide to turn lights on, leave open, turn on map lights inside. Shut the door, walk away and in less than 10 minutes all lights are off!

Just for comparison, my E-Ray with it's very low charge reduction when parked, if I don't drive for a week when I start it, dash voltage reads only 0.1 to 0.2 volt higher then the 80% charge of 13.3 volts. Within 5 miles it drops from 13.4 or 13.5 back to 13.3 volts, fully charged (fully as far as GM wants, which is ~80%!)

Yep I agree IF you keep a lead acid battery (NOT Li-Ion) on a charger the battery will last longer. That is my experience with my Street Rod that now only goes to car shows. I have my old GM equivalent CTEK charger bought in 2014 connected 24/7. My Yellow Top batteries have lasted a long time in my 25 year old Rod. BUT my DD Vettes when I want to drive and when I return don't want to mess with a charger. Not needed.

 

Although storage was not the original question - the discussion seems to be at least partly about that.

Based on the description of the charging system for the Stingray in the manual, and the summary of it that I posted in post 32, the system targets an 80% state of charge for the battery. Most of the time, when it estimates the battery SOC at 80% it will switch to the fuel economy mode. It is described like this:

"Its targeted generator output voltage is the open circuit voltage of the battery and can be between 12.5-13.1V. When fuel economy mode is active, the generator is not charging, only maintaining open circuit battery voltage."

You could drive it a 1000 miles and the battery SOC will still only be 80%. That's fine if the car is going to sit unused for just a few weeks. In the "Getting to Know Your Corvette Guide" that used to come with car, but does not anymore, GM says "If the vehicle is not driven weekly, or the battery is disconnected or drained, use the optional battery maintainer to charge the battery." But experience reported on the forum indicates you can go longer than that.

But if storing the car longer, I think its best to put it on the maintainer if you can. If not, at least use the maintainer or charger to fully charge the battery to 100% SOC before storing it. Optionally remove the battery and store it on a maintainer.

Daily use of the maintainer might depend on how often you drive the car. Its been said the what actually shortens battery life is "charge/discharge cycles". So, if you have charged the battery to 100%, then when you drive the car, it will actually (according to Service Manual description) enter the fuel economy mode and allow the battery to discharge to 80% where it will maintain that SOC. Then if you put it back on the maintainer/charger, it charges it back up to 100%. If you do that everyday, that may be a charge/discharge cycle between 80% and 100% SOC. So if that theory holds, it would suggest that you not use if you drive the car every day. I drive mine less frequently, so I put mine on the maintainer when it is parked.