OptimaJim

khoeysr, I don't know how you are defining “fully charged” but 11.8 would definitely not be anywhere near fully-charged for any 12-volt battery. That voltage level is probably at least 70% discharged or more, depending on the battery. A voltage level of 12.6 after shutting your car off could be a surface charge that would drop back down significantly to a much lower voltage level once that surface charge dissipates. 11.3 volts might not be completely discharged, but it is very close to it.

I would agree with skinner1961's advice about disconnecting a fully-charged battery on a vehicle being stored for a long period of time and that periodically starting it while in storage will do more harm than good to the battery. The reason, as skinner1961 indicated, is because the energy consumed by the vehicle during storage and starting will probably not be replaced by the alternator while the car is running for a brief period of time. That means you are moving your battery closer to a discharged state by starting it periodically, than if the battery just sat and a vehicle wasn't started at all. Rock'n Blue 08 is also correct about alternators being designed to maintain batteries near a full state of charge, not recovering batteries that have been deeply-discharged. Alternators asked to perform that task can end up failing prematurely.

Jim McIlvaine
eCare Manager, OPTIMA Batteries
www.pinterest.com/optimabatteries

khoeysr

I am the OP.

Optima Jim, I really appreciate a guy with your expertise staying in this thread.

I didn't have the multi meter when the battery was "fully charged" back on 12/22, so I didn't have any voltage readings. It looks like the readings that I have been recording (high 11s) are low, which would seem to explain why the car wouldn't start the other day when the start out voltage was 11.3.

I am thinking that I may disconnect the battery and just leave it until better weather comes, as many have suggested. Since I don't have access to power for the battery tender, it would just be more of the same.

I appreciate the input from everybody. Feel free to keep it coming.

cyberay

Why not remove the battery and bring it inside and put it on a tender? Then you would at least have a serviceable battery when you're ready to use the car again.

A discharged battery can freeze and that will be the end of it.

OptimaJim

khoeyser, as skinner1961 mentioned, simply disconnecting the battery isn't enough. You need to make sure the battery is fully-charged (at least 12.6V) when you disconnect it. While flooded batteries self-discharge at a higher rate than AGM batteries, it should still be able to hold enough voltage when fully-charged and disconnected, to get your car started after a few months. I would advise fully-charging the battery again, when you bring your vehicle out of storage.

Jim McIlvaine
eCare Manager, OPTIMA Batteries
www.pinterest.com/optimabatteries

khoeysr

I am the OP.

Just an update for anyone who cares.

My car has been starting of late, even though the start voltage is around 11.3. No DIC messages, nothing unusual. No changes in where it is stored or the conditions (winter).

Haven't been back to the dealer yet.

robertbruce

Use the battery tender. End of problem.

OptimaJim

khoeysr, as robertbrucef suggested, it sounds like it's time for you to replace your current battery maintenance device, as it is clearly not getting the job done.

Jim McIlvaine
eCare Manager, OPTIMA Batteries
www.pinterest.com/optimabatteries

Glen e

moat of you guys should read before you post, about getting a maintainer...his first sentence in the first post is:

My car is stored in a commercial storage unit without access to power

khoeysr

I am the OP.

Sorry you got worked up, Glen. This is a long post and not everybody reads the whole thread.

The story here is when I first put the car away, it was dead, completely dead, before a week has passed. I have no access to power where i store the car. The point was that the car should not be dead after that short of a time. The battery tender was irrelevant. The popular opinon is that there is some sort of parasitic draw, even though the dealer claims the battery is perfect and they found nothing.

Of late the car has been starting, and is not stone dead when i visit it at 4 or 5 day intervals. Voltage measured by a multimeter before starting is still low, according to some who seem to know what they are talking about.

So my opinion is that there is still something to check out, but the effect has lessened over time. Weather here in central NY has kept me from getting it back to the dealer.

Edward Weaver

I heard if you leave a USB flash drive plugged in it will continue to draw down the battery. Just another thing to check.

slvr 07

stored my 07 vert. in the garage for 4 winters. i purchased a battery tender on ebay for around 35.00. i hooked it up every winter and come spring the vert. would start right up, with no problems. i also change oil prior to winter and add stabil to the gas tank...

OptimaJim

Glen_e, I have read this thread several times from the start, but I appreciate the reminder about Kevin's car being stored in a location without electrical access. However, Kevin has also indicated in this thread that he would charge his battery and on the 8th of this month, he indicated he would probably just disconnect his battery while the car was in storage.

I doubt Kevin would keep bumping this thread because he likes the attention, so if he is attempting to fully-charge his battery and is disconnecting it when he puts his car in storage, as he already indicated was his plan, his battery should not be measuring 11.3 volts when it comes out. Either the charger isn't doing it's job or the battery has an issue, because no battery should drop voltage in that short amount of time when disconnected from a vehicle, as Kevin indicated was his plan.

I have posted a link to a video explaining how to measure parasitic draw more than once in this thread, but I haven't seen a number on that yet from Kevin. It would be interesting to know what he measures, in the event that he doesn't disconnect his battery when he stores his car. There is no opinion on whether C7s have a parasitic draw. They do and that is a fact. The only question is how significant of a draw they have.

Jim McIlvaine
eCare Manager, OPTIMA Batteries
www.pinterest.com/optimabatteries

khoeysr

I am the OP>

Optima Jim, the last time the battery was charged was on 12/22. Since then it has been starting. The multimeter voltages before starting are running 11.3. There was one time it didn't start, but the majority of times it did. I have no power for the tender and have not disconnected the battery.

That parasitic draw thing is above my pay grade with the multimeter right now.

I'm not trying to make this a novel (too late) but I am looking for some quality input (which I have certainly been getting) as well as provide some information for anyone who may have a similar problem. Doesn't look like it is widespread, which is always good.

Glen e

so after all the "advice" you are doing nothing different, right?

it's all been said - Listen to Jim - maintaining a batt at 11.3 will destroy the batt long term. take it out, charge it to max 12.6 or so and then install and disconnnect it....no more posts from me.......

skinner1961

are you serious
quit starting it and unhook the battery, like everyone else does if they cannot put a tender on it

JerryU

Curious if others have measured battery voltage in a C7? Just checked my volt meter at Batteries Plus and their calibrated Fluke matched my quality VOM, 12.85 volts on a battery on their shelf. Here is my situation. When this thread started decided to check my OCV and it was 12.4 volts. Put my old charger on and in about 8 hrs of a low amp charge it showed fully charged. After 24 hrs still read 12.4 volts. Decided to buy a CTEK 3300 charger (similar if not the same as the Corvette charger) to see if this modern 4 mode charger would be better. Showed full charge after a few hrs so removed and after 24 hrs it still reads ~12.4 volts. Getting cold so put the charger on AGM/Cold setting. Showed fully charged quickly and while in maintenance mode shows 12.5 volts. Not sure what type of Delco battery it is. It does show a 48P size, and Delco shows an AGM battery with a similar designation. I checked all battery connections and the voltage across terminals to post which showed 0 voltage drop while on a low current draw. If OptimaJim is reading this post, I have a Schumacher charger on my 3 year old Yellow Top Optima and it shows 12.8 volts after being removed for 24 hrs. However all batteries appear to be different and the additives, i.e. calcium etc effect the OCV properties.
Note, car is starting fine but driven only a few days a week with the cold weather we’re having even in SC! Called service manager at the dealer and he says not to worry. Curious. Anybody has anyone checked voltage readings with a C7? Any feedback if the C7 Delco is Absorbed Glass Mat (AGM) construction?

OptimaJim

Hi Jerry,

While there are a lot of good chargers on the market to choose from, if we thought every charger out there did a good job, we'd have never created our own line. Fully-charged our YellowTops should measure about 13.0-13.2 volts, but we always say "about," because it's ok if a battery's voltage doesn't fit exactly within that range, but close to it.

As batteries age, they can show lower voltage levels fully-charged and as you indicated, the chemistry of batteries can vary by brand, manufacturer and type, which is why our RedTops are fully-charged at about 12.6-12.8 volts. Sometimes when sulfation has formed in a battery it will struggle to hold higher voltage levels. Sometimes this sulfation can be reversed to some degree by cycling a battery a few times down to about 11.5 volts and then using a 10-amp charge to bring it back up to a full state of charge. In fact, I'm doing that with a couple of our batteries right now.

Kevin, as Glen pointed out, sound advice has been offered to you in this thread. If you choose not to implement any of it, then you are bound to continue having issues as long as you own your car. You will not be alone, as I anticipate more than a few C7 owners will have similar issues under similar circumstances, through no fault of the car or battery- they are what they are.

If measuring parasitic draw is above your pay grade, my last piece of advice to you, would be to buy this quick disconnect at your local auto parts store and have your dealer install it for you-

One twist of the green **** and you will be able to disconnect your battery when you park your car. Good luck.

Jim McIlvaine
eCare Manager, OPTIMA Batteries
www.pinterest.com/optimabatteries

georgied

I was about to suggest the same disconnect. I used to use them a lot in marine applications. Simple and effective.

JerryU

Thanks for the feedback. Never had to use a charger on the C6, even before I found the leak with several cells low on acid. Replaced that battery with an Optima. However the C7 is my daily driver when it is not so cold! The tires on the Z51 have poor traction below about 40F and today the high will be 32F. However it will be 50+ for the next 2 days and 65 on Monday-so we’re not nearly as bad in SC as other parts of the country! Will use the wife’s SUV today!

Ronnie wilkins

One other question guys. If you leave a battery hooked up al winter with very little or no use won't that start making your aluminum look bad and other metal parts? Not only that I have also noticed carpet discoloration on some cars even though they are in a closed garage with no direct sun light. I have also had one car I left in the garage with an aluminum can in the bed of it (El Camino) and the can looked kinda tarnished and greenish tint. I s that battery damage of some sort? Does it hurt for these cars not to have power to the electronics for a 6 month period?