Dead battery question
Thread Starter
Melting Slicks
Joined: Jan 2021
Posts: 2,032
Likes: 228
From: Colorado Springs, CO
Dead battery question
As some of you may recall from a prior post, I underwent brain surgery in early October. I'm pleased to report the pathology report is negative, the sample tissue was benign and from the latest imaging the tumor does not appear to be regrowing. I've relearned how to walk and am now on to fine motor skills - tying shoelaces, etc. Still a mountain to climb, but I'm in a much, much better spot than just a few short months ago.
The C6 has been sitting under its cover in the garage since mid-September. Yesterday I decided to go out, fire it up for a few minutes, let fluids circulate a little, etc., and needless-to-say...dead. What's my best course of action? The battery is not terribly old and should have years more life in it - but - I've no way of knowing how long until I can drive again, i.e., how much longer that black beauty will just be sitting there collecting dust. Would it be stupid to jump start it, get a charge back on the battery, then have it sit there for another x months only to die again? Is that excessively hard on a battery? Would I be better off just leaving it dead until I'm again able to drive it on a regular or semi-regular basis? Jump start it, then just be sure to go out and fire it up a few times a month? ...what..?..
The C6 has been sitting under its cover in the garage since mid-September. Yesterday I decided to go out, fire it up for a few minutes, let fluids circulate a little, etc., and needless-to-say...dead. What's my best course of action? The battery is not terribly old and should have years more life in it - but - I've no way of knowing how long until I can drive again, i.e., how much longer that black beauty will just be sitting there collecting dust. Would it be stupid to jump start it, get a charge back on the battery, then have it sit there for another x months only to die again? Is that excessively hard on a battery? Would I be better off just leaving it dead until I'm again able to drive it on a regular or semi-regular basis? Jump start it, then just be sure to go out and fire it up a few times a month? ...what..?..
Race Director
Joined: Nov 2017
Posts: 12,759
Likes: 10,657
From: Prosper TX/Austin TX
2020 C6 of the Year Winner - Modified
Batteries are cheap ($129 at Costco) and so are battery tenders (CTEK ~$100 on Amazon). Buy a new battery & buy a tender. Keep it connected when not driving 
Melting Slicks
Joined: Apr 2019
Posts: 2,515
Likes: 1,167
From: Northern Wisconsin
When you put the car away, it sounds like you just shut it off and that's it. If that is the case, there is no wonder that the battery is dead now. There may be nothing wrong with the car itself. The best thing to do is keep it on a battery maintainer when not being driven. If you can't do that, then at least disconnect the negative battery cable from the battery when storing for the winter. Your battery may still be OK, but you won't know until you charge it up somehow. I would get a 2 to 6 amp battery maintainer and hook that up for a few days, and then see if it will start. My first choice is the
. At 5 amps, it has enough umph to charge a dead battery in a reasonable amount of time, then it automatically will switch to maintain the battery without overcharging for as long as needed.
Safety Car
Joined: Sep 2007
Posts: 4,009
Likes: 491
From: South Florida
Congrats on the benign news. I had two bouts of cancer myself and I know how stressful waiting for pathology can be. As for the battery, these cars tend to kill them pretty quick. I would either get a battery tenders as others suggested, or just disconnect the negative terminal if it's going to sit for a while. I paid around $270 for a "top tier" battery from advanced auto parts with a two year warrants so theyre not too expensive. Sure you can spend $500 on some of them and MAYBE get a little extra longevity, but I had one in my grand sport that doesnt get driven every day last for almost four years and I don't know for certain if it was a brand new battery from the dealer when I bought it because we couldnt find a date code. Best of luck for a quick recovery, enjoy life and that car as soon as you can!
Safety Car
Joined: Feb 2016
Posts: 4,455
Likes: 1,390
From: SC
Fully discharging a battery does permanent damage. You may or may not be able to bring it back to life. A lot of chargers won't even try to charge a fully dead battery because they see 0 volts and don't think anything is connected. If you do try to charge it (and I would), I would take it out of the car. There is going to be a lot of out gassing of hydrogen.
I would certainly not jump start it. Alternators are meant to top up functioning batteries, not bring them back from the dead. If you do jump start it, there is going to be a large current inrush when you first hook another battery and alternator to it. You will have to wait several minutes before the voltage comes up enough to try to crank. Then the load on the alternator will be very high trying to charge the battery. Much better to let a battery charger do all that if it can.
I would just wait until you are ready to drive it, put a new battery in then and be done with it.
I would certainly not jump start it. Alternators are meant to top up functioning batteries, not bring them back from the dead. If you do jump start it, there is going to be a large current inrush when you first hook another battery and alternator to it. You will have to wait several minutes before the voltage comes up enough to try to crank. Then the load on the alternator will be very high trying to charge the battery. Much better to let a battery charger do all that if it can.
I would just wait until you are ready to drive it, put a new battery in then and be done with it.
Thread Starter
Melting Slicks
Joined: Jan 2021
Posts: 2,032
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From: Colorado Springs, CO
Pro
Joined: Oct 2024
Posts: 725
Likes: 398
From: WI
I would try charging the battery first. It may have plenty of life left in it if allowed to fully charge. After that - use the same charger to maintain it. Most smart chargers these days will automatically switch between bulk charge, topping off, and maintenance charging.
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Safety Car
Joined: Aug 2013
Posts: 4,429
Likes: 605
From: Minneapolis Mn
Couple of things I've read, other I know. Pull the On-Star fuse out of the fuse block. It's supposed to draw juice continually. If your car is a manual, be sure to put it into reverse (think that's what it is) when stored, it shuts some stuff down that otherwise would draw juice. Make sure things like the glovebox light, mirror lights, hood light and trunk light are off. I wired a battery tender onto my car and ran the wire up to the grill so I can plug it in even if the hood is closed. I keep my windows closed due to mice around the area (use the usual mouse killer etc.) and release the hood and put a piece of Styrofoam between the windshield and the edge of the hood so I can open the hood regardless without a lot of hassle.
To the OP, your scenario sounds a lot like storing a car for the winter and I'd treat it similarly. Good gas, can of Seafoam, tires pumped up, clean interior, check the coolant and oil. Start the car every 3-5 weeks, let it come up to operating temp. Move it back a few feet and then forward to the parking spot.
I think if you do that, when you're ready to drive again, it will be ready to go.
Congrats on your diagnosis and hope it continues to improve.
To the OP, your scenario sounds a lot like storing a car for the winter and I'd treat it similarly. Good gas, can of Seafoam, tires pumped up, clean interior, check the coolant and oil. Start the car every 3-5 weeks, let it come up to operating temp. Move it back a few feet and then forward to the parking spot.
I think if you do that, when you're ready to drive again, it will be ready to go.
Congrats on your diagnosis and hope it continues to improve.
Melting Slicks
Joined: May 2020
Posts: 2,135
Likes: 1,309
From: North Little Rock, AR
I remember your past post and this is great news you are doing better.
I would not buy a battery now, just wait until you are ready to drive it.
You could buy a maintainer and hook up to existing battery. Possible it will come back to life.
I would not buy a battery now, just wait until you are ready to drive it.
You could buy a maintainer and hook up to existing battery. Possible it will come back to life.
Heel & Toe
Joined: Mar 2025
Posts: 17
Likes: 4
I agree with JABCAT! Buy yourself a trickle charger and keep it always hooked up! If you don't have a battery charger? Just hook up the trickle charger to it and it will slowly bring back your battery to full charge!
Melting Slicks
Joined: Nov 2007
Posts: 2,282
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From: Pittsburgh PA
St. Jude Donor '10-'11-'12-'13-'14
As some of you may recall from a prior post, I underwent brain surgery in early October. I'm pleased to report the pathology report is negative, the sample tissue was benign and from the latest imaging the tumor does not appear to be regrowing. I've relearned how to walk and am now on to fine motor skills - tying shoelaces, etc. Still a mountain to climb, but I'm in a much, much better spot than just a few short months ago.
Drifting
Joined: Oct 2003
Posts: 1,503
Likes: 30
From: Uniontown Alabama
Thread Starter
Melting Slicks
Joined: Jan 2021
Posts: 2,032
Likes: 228
From: Colorado Springs, CO
My mobile mechanic had to come today to do some work on our son' car anyway and so brought his charger. The battery seems to be coming to life and in pretty good shape. He started it off at 20v and says that as soon as connected the headlights & serval other electrical functions immediately came to life. He left it on 20v while he was here, then dropped it to 10v and says I should put it on 2v later today and he'll be back in a few days to pick it up and recommends keeping it on a 2v trickle while I'm not driving it. I'm on eBay now and it looks like the typical, minimum fixed trickle charger is 12v. Should I just get the 12v and leave it connected (for month's on end), or is that really a little too much voltage?
Pro
Joined: Oct 2024
Posts: 725
Likes: 398
From: WI
My mobile mechanic had to come today to do some work on our son' car anyway and so brought his charger. The battery seems to be coming to life and in pretty good shape. He started it off at 20v and says that as soon as connected the headlights & serval other electrical functions immediately came to life. He left it on 20v while he was here, then dropped it to 10v and says I should put it on 2v later today and he'll be back in a few days to pick it up and recommends keeping it on a 2v trickle while I'm not driving it. I'm on eBay now and it looks like the typical, minimum fixed trickle charger is 12v. Should I just get the 12v and leave it connected (for month's on end), or is that really a little too much voltage?
Thread Starter
Melting Slicks
Joined: Jan 2021
Posts: 2,032
Likes: 228
From: Colorado Springs, CO
Pro
Joined: Oct 2024
Posts: 725
Likes: 398
From: WI
Yes 2 amps is a pretty standard current to charge at. Fairly low and slow which is good. The Genius5 I mentioned will charge at a max of 5A and lower the current as needed as the battery reaches full charge.
Thread Starter
Melting Slicks
Joined: Jan 2021
Posts: 2,032
Likes: 228
From: Colorado Springs, CO
