Corvette C6 Battery Concerns

The C6 Corvette is a true World Class performance car with excellent “daily driver” attributes. Everywhere you look on the C6, an electronic device is operating something we had to either manually perform or think about previously. All of these electronic gadgets require stable voltage for long life. The days of removing the battery cable to see if the charging system is working are long gone. The C6 Corvette battery has to maintain all of the electronic requirements while effortlessly starting the car. In light of this, we typically have very little thought about servicing or checking the battery. They sit there without attention until we have difficulty starting our car.

This is a sign of acid leakage from the side post. We see this very often and have to replace many electrical components due to this leakage. Using an Optima Battery minimizes this concern dramatically.

Lead-acid batteries have been the mainstay for decades, going through just a few changes. The original tar-topped hard rubber case was replaced in 1968 with a plastic composite case. This helped stop the rubber case model’s inherent acid leaks. On many GM models, side post batteries replaced top posts. The side posts worked well until they leaked acid. One had to be easy with the wrench when tightening the side terminals or he could loosen the post in the battery case.

Fast forward to the nineties, when AGM and electrolytic gel batteries alleviated the problems with caustic acid leakage. AGM batteries use an absorbent glass mat with electrolyte paste tightly wound around lead plates. Optima batteries are AGM battery technology at its finest. The tight fitting plates encased in individual cells limits vibration that ultimately kills the best of the early battery designs. The spiral cell AGM Optima battery has the best of both worlds covered, as leakage concerns and vibration damage possibilities are minimized.

Electrolytic gel batteries typically use the same design as their predecessors: lead plates stuffed into a case with electrolytic gel surrounding them. Gel’s benefit is less leakage concern. Three things that put any battery to the test are extreme cold, heat and vibration. The optimum temperature for lead-acid batteries is 77 degrees Fahrenheit. As temperatures rise, battery lifespan is shortened. Likewise, lower temperatures slow the chemical process, straining the battery under high cranking loads.

Why should you care about what battery you have in your C6? The answer lies in the placement of the battery: directly over the Powertrain Control Module (PCM) and several wiring harnesses. Battery acid leakage and voltage spikes may damage these electric components.

We have witnessed wiring harness damage that required many hours of repair with high labor costs. In one particular case, battery acid damaged the a/c system’s vacuum supply tubing. We had to strip the main wiring harness back to the firewall in order to replace the tubing routed with the wiring. This could have been avoided with an Optima or gel-cell battery. Owners spend plenty of time figuring out what upgrades make sense on their Corvettes without considering the battery, yet they sometimes neglect to consider that replacing the OEM battery makes sense as an upgrade and a safety precaution.

If you have a gel cell or OEM style lead-acid battery that sits for prolonged periods of time, you may be damaging the battery. Electrolytes (sulphuric acid) will eventually sulfate the battery and limit its capacity. Discharging and charging keeps all types of batteries active and prolongs life. Damage occurs every time your battery is discharged below the 75%-80% mark. Battery drain is inevitable from lack of activity. The C6 Corvette’s multiple memory systems also contribute to voltage loss. An excellent option is to install an Optima Yellow Top Deep Cycle (PN 171132), whether you store your C6 or drive it infrequently. You can also prolong your battery’s life with a Battery Tender Plus (PN 171251). This maintains a specific charge level above 12.6 volts while compensating for temperature variations. If you store your C6 in a heated garage, you consider the Battery Tender Junior (PN 171217). It will constantly monitor the battery’s charge state, charging if necessary. This cyclic activity keeps the battery at full charge and top condition.

Dead Batteries Are Inevitable

No matter how careful you are, there will be times when a dead battery catches you off guard. How you handle the situation can save you plenty of grief and potential bodily harm. To begin with, Corvette owners who do not carry their key should consider an Emergency Entry Access System (PN 176062) to easily connect a power source to open the door. This system will get your doors to unlock so you can pop the hood and connect jumper cables.

Jumper Cables

With this in mind, remember that every time jumper cables are used to start your C6, there is a potential for a major voltage spike when the cables are disconnected. The alternator sees a major current loss as the cable is removed and spikes voltage momentarily. In some cases, everything seems fine, but then, out of the blue, an electronic component has a failure soon afterward. The best policy with a dead battery is to charge it before starting the car. We all know that this will not be possible to do at times. If you find yourself in this predicament, leave the jumper cables on for five minutes before attempting to start the engine. After the engine starts, leave the cables on for another five minutes to allow the charging system to stabilize. Always connect the negative cable last and disconnect the negative cable first. Jumper cable instructions warn you to connect the negative cable at an engine location rather than the battery’s negative terminal. This is to prevent explosion of the inherent gasses that all batteries have venting in the area of the terminals. In the side post battery’s case, the vents are on the top and still close to the dangerous gasses. Using the alternator to bring the battery back to full charge adds significant load and heat to the alternator. Alternator life will be shortened significantly if it is constantly working at full capacity from a weak battery. Likewise, if your battery is consistently dying because of a draw, operating the alternator at full capacity will shorten its life.

Consider investing in a quality set of jumper cables. Cheap jumper cables have very little copper wire and melt easily unless you’re trying to jump start your riding lawnmower. We see many jumper cables with impressive insulation, yet only 10 gauge wire coursing through it (remember that as wire gauge increases in size, its gauge sizing decreases). A minimum 4 gauge cable should be used for jump starting. You can expect to pay a minimum of $60.00 for good jumper cables.

Battery Charging Techniques

In the event that your battery dies, there are specific charging requirements for each type of battery construction. A good battery can be destroyed forever if improper charging techniques are used. Excessive heat during charging can warp the plates, causing permanent damage. Let’s start with the battery’s condition. There are two likely dead battery scenarios: either the battery has drained from sitting an extended period of time, or interior or exterior lights were left on. If the battery is completely discharged from an extended period of dormancy, there is a chance that the battery may not come back to life.

Safe battery chargers have voltmeters to monitor the charge voltage level. Charge voltages should not exceed 15.5 volts and 10-12 Amps.

OEM Type Lead-Acid and Gel Cell

To see if the lead-acid or Gel Cell battery will take a charge, start with the battery charger set on high for a half hour. This warms up the electrolyte and begins to release the sulfation paste that is surrounding the lead plates. The battery charge indicator gauge will likely show no movement (battery is not accepting a charge) within the first half hour. If the battery is salvageable, the charge indicator needle will move up to the 14-15 volt range usually within the half hour. At that point, the charger should be switched to the medium or low position. The charger should be left on for a minimum 12 hours. In most cases, a completely discharged battery can take 18-24 hours to be fully charged. If the charger volt gauge is working properly, you can tell that a battery is fully charged when the charge indicator needle moves to the 13.0 volt position. Keep in mind that many battery chargers have a rough life, causing gauges to malfunction. A Hydrometer is the best test for battery condition and charge.

With the battery charger set on the high position, monitor the charger’s volt gauge. If the gauge needle does not move off the 13.0 volt area within one hour of charging, your battery should be replaced. Commercial battery chargers have four settings: low, medium, high and cranking. When you connect the charger, start at the low setting to see if the charger voltmeter moves. As you go up to the high position, the voltmeter should rise another volt. This is a good indicator that the battery will accept a charge and has life left. Be very careful with the charger set on high, as overheating can occur after an hour.

Voltmeter Reading

When you start your C6, the voltmeter should be in the 13.4 area. As you drive, the voltmeter reading should rise to the 14.0-14-6 area. This indicates that the battery has topped off and is fully charged. The rule of thumb is that an alternator’s voltage output is lower when it is charging higher amps. When the battery nears full charge, the alternator’s amp output drops and voltage rises. Keep in mind that not every gauge is perfectly calibrated; the numbers quoted are typical and can vary. What’s important is the change in voltage output. If the voltage is always low, the battery is dying. Another possibility is there is a major battery draw somewhere. In this case, it would take a long run for the voltage gauge to rise.

Optima AGM

Optima Red Top Charging Information

The following charging methods are recommended to insure a long battery life. Always use a voltage-regulated charger with voltage limits set as described below.

Red Top Type: 34 & 34R – 34/78 – 78 – 25 & 35 – 75/25
These batteries are designed for engine starting applications. They are NOT recommended or warranted for use in deep cycle applications.

Recommended charging information:


  • 13.3 to 15.0 volts, no amperage limit.

Battery Charger:

  • 13.8 to 15.0 volts, 10 amps maximum, 6-12 hours approximate.

Rapid Recharge:

  • Maximum voltage 15.6 volts (regulated), no current limit as long as battery temperature remains below 125°F (51.7°C). Charge until current drops below 1 amp.

Float Charge:

  • 13.2 to 13.8 volts, 1 amp maximum current, time indefinite (at lower voltage).

All limits must be strictly adhered to.

Safety Information:

  • Always wear safety glasses when working with batteries.
  • Always use a voltage regulated battery charger with limits set to the above ratings. Overcharging can cause the safety valves to open and battery gasses to escape, resulting in premature failure. These gasses are flammable! You cannot replace water in sealed batteries that have been overcharged. Any battery that becomes very hot or makes a hissing sound while recharging should be disconnected immediately.

Failure to fully charge a battery can result in poor performance and a reduction in capacity.

Courtesy of Optima Battery

Warranty Concerns

Purchasing a new battery is a major expense as we all know. If you are required to buy a new battery make sure to keep your receipt. Place the receipt in the glove box or console with your warranty and owners manual. Today we see suppliers come and go getting a good deal is sometimes costly. Make sure you buy from a reputable supplier and if the inevitable happens you move or the company goes out of business. Your receipt will get you another battery in the case of failure. In the case of Optima batteries call the company directly explain your situation. Let them know that your supplier is too far away for instance and see what they can do for you.

Story and photos courtesy Chris Petris

2 thoughts to “Corvette C6 Battery Concerns”

  1. I have heard that if you park the car, leave it in reverse and set the hand brake this will virtually eliminate parasitic draw on the battery. Is this correct?

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