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Battery voltage on new GS

 
Old 03-24-2019, 11:11 AM
  #21  
laserdude2215
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Thirteen volts is way too low! I would suspect the alternator, but it could be an indicator problem. That's assuming that the dealer's battery test was valid.
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Old 03-24-2019, 11:12 AM
  #22  
JerryU
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The C7 is different than in the past! The computer controls the charging rate, like it does oil pressure and many things in today's cars. That is why you will occasionally see a step in the voltage on the dash gauge. Unlike alternators of old it will go to a lower setting when fully charged. 13 volts is just fine as your battery appears to be fully charged! Especially with that long drive.

Now what is fully charged? First a drive of >75 miles will fully charge a DD (assuming it was fully charged when parked.) Not 5 miles!

The C7 is not bad on batteries. In fact it has circuits to shut down all electrical "stuff" after ~5 minutes. Leave a light on it will shut that off as well. Leave the hatch up (as when you're changing with the Chevy charger and the interior lights will go off in ~5 minutes. It will come on for a few seconds to send a signal to OnStar for example but shut down very quickly.

I seldom use my equivalent to the Chevy logo charger (same brand and 40% cheaper without the logo!) Been on vacation for 2 1/2 weeks and no problems. But going on a long cruise so will use it next week! It will extend the battery life as apposed to leaving it often for a week of so.

PS: By the way, the only way to check battery voltage with a meter is AFTER the surface charge is depleted. Car needs to sit for 6 to 12 hours. I check at the terminal on the alternator (remove the rubber boot) and a good ground on a chassis bolt. Pic is from the C7 Service manual. Note 12.75 is fully charged. That is average but batteries will vary. Note it says wait 12 hours. Checking at the battery terminals is a PIA in the C7! The alternator terminal will be at the same voltage with any (even cheap) digital meter as the meter current draw is very low so no voltage drop.

Last edited by JerryU; 03-24-2019 at 11:25 AM.
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Old 03-24-2019, 11:16 AM
  #23  
ShadowGray19
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Originally Posted by Mark230 View Post

However I notice that my battery voltage rarely goes above 13 and if it does, it quickly drops back to 13 and sometimes slightly below.

Wondering if its a good ideal to use battery charger which came with car (CTEK 3300) and charge battery over night?
Mark:

I have a 2019 Stingray with 550 miles and the gauge shows exactly the same as yours. As others have said, the voltage is going to show a lower reading when your battery is new and at or near a full charge. I had the same concern about a new Charger I bought in 2016. The voltage readings were always at or near the low 13 range when the car was new. As time went on, the voltage readings went up while driving the car. When I traded it in on my Corvette the voltage readings were usually between 14 - 14.5 while driving. When I first got the Charger I asked the same questions you are now asking. A 30 year FPA tech gave me an explanation that may also be helpful to you in understanding what is going on with our cars.

"The Power Control Module (PCM) keeps the field as weak as possible, while still maintaining adequate voltage to meet system load demands and battery State of Charge (SOC). The weaker the field, the lower the parasitic load on the engine, thus increasing fuel efficiency. System voltage is dependent on a number of factors, including but not limited to battery SOC, system load and calculated battery temperature. A cold/frozen battery requires higher voltage to recharge than a warm battery. Therefore, a weak/discharged battery in cold climate (-10*F/-23*C) may result in a measured voltage of 15+ volts. Whereas a fully charged battery in warm climate (90*F/32*C) may only see low 13 volt range."

I use my CTEK chargers (Multi US 7002 and MUS 4.3) to periodically "top off" the batteries on all my vehicles. I do not leave them plugged in all the time due to frequent electrical storms we have here in FL. Do not want any electrical spikes to damage vehicle electronics.

Dave

Last edited by ShadowGray19; 03-24-2019 at 11:23 AM.
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Old 03-24-2019, 12:25 PM
  #24  
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Originally Posted by JerryU View Post
The C7 is different than in the past! The computer controls the charging rate, like it does oil pressure and many things in today's cars. That is why you will occasionally see a step in the voltage on the dash gauge. Unlike alternators of old it will go to a lower setting when fully charged.
Sorry but this is just plain wrong.

"Alternators of old" did the exact same thing, only via a different mechanism perhaps and maybe not as precisely

Last edited by KenHorse; 03-24-2019 at 12:25 PM.
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Old 03-24-2019, 12:57 PM
  #25  
Mobil 1
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Surface charge can be removed by turning headlights on for about 30 seconds.
Cars have had computer controlled alternators for years and years, nothing new here.

Last edited by Mobil 1; 03-24-2019 at 12:57 PM.
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Old 03-24-2019, 12:58 PM
  #26  
JerryU
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Originally Posted by ShadowGray19 View Post

"The Power Control Module (PCM) keeps the field as weak as possible, while still maintaining adequate voltage to meet system load demands and battery State of Charge (SOC). The weaker the field, the lower the parasitic load on the engine, thus increasing fuel efficiency. System voltage is dependent on a number of factors, including but not limited to battery SOC, system load and calculated battery temperature. A cold/frozen battery requires higher voltage to recharge than a warm battery. Therefore, a weak/discharged battery in cold climate (-10*F/-23*C) may result in a measured voltage of 15+ volts. Whereas a fully charged battery in warm climate (90*F/32*C) may only see low 13 volt range."

Dave
Originally Posted by KenHorse View Post
Sorry but this is just plain wrong.

"Alternators of old" did the exact same thing, only via a different mechanism perhaps and maybe not as precisely
Totally different! Read the post above, it's done to reduce the wasted energy the alternator systems "of old" caused. Yes as the battery voltage increased less current was going into the battery but it was NOT controlled as today's systems are- by computer. Now agree alternators were better than the generators I have on '41, '50 Ford etc that used relay's to regulate charging rates but alternators did NOT make the "step changes" we see on the C7.

It's like the reason oil pressure changes today. Sure it always did with a max pressure spring/valve that directed oil around the pump but today it's controlled by a truly variable volume pump, by computer to reduce wasted pumping energy when not needed. That also creates step changes a new owner, used to Vettes etc "of the past" may cause concern.


Last edited by JerryU; 03-24-2019 at 01:03 PM.
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Old 03-24-2019, 01:19 PM
  #27  
JerryU
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Originally Posted by Mobil 1 View Post
Surface charge can be removed by turning headlights on for about 30 seconds.
Cars have had computer controlled alternators for years and years, nothing new here.
My C6 did not show step voltage changes nor did the C6 Service Manual talk about the energy saving features and why they occur! Perhaps some other cars but not my C6.

The C7 Service Manual states: "The electrical power management system utilizes on-board computer capability to maximize the load, improve battery state-of charge and life and minimize the systems impact on fuel economy.
It monitors the battery voltage and estimates battery condition and takes corrective action by adjusting the voltage."

Lots more in a number of paragraphs, like it communicates with the Body Control Module, Battery Current Sensor and Engine Control Module - defines battery temp etc. etc!

This Old Post from NSC5 is a Better Explanation:
The voltage will vary a lot when driving and a system reading in the low 12 volt range while the engine is operating can be entirely normal. The alternator output is controlled via its field winding to provide the desired current output and it may be reduced for a number of reasons one of which is to improve fuel economy under some driving conditions.

As long as the voltage does come up to a reasonable charge rate at times the alternator and charging logic control is likely fine. Checking battery voltage under load is the best determinant of remaining battery life.

The operating voltage level in modern vehicles varies a lot more than it used to in the old days when simple internal or external regulators were used to control alternator output but with the new smart controls built into the ECM alternator current output, and thus system voltage, will vary widely to meet different conditions.

Last edited by JerryU; 03-24-2019 at 02:06 PM.
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Old 03-24-2019, 02:12 PM
  #28  
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Originally Posted by JerryU View Post
Totally different! Read the post above, it's done to reduce the wasted energy the alternator systems "of old" caused. Yes as the battery voltage increased less current was going into the battery but it was NOT controlled as today's systems are- by computer.
Maybe we're splitting hairs here.

Even the old style electro-mechanical voltage regulators (even when used with alternators), did exactly the same thing as you're describing above - as the battery voltage came up, the regulator lowered the voltage going to the alternator's field winding, hence lowering the amount of current being delivered (by way of lower voltage delivered. Remember, power is power).

Later generation alternators (like Delcos) incorporated a solid-state voltage regulator (usually integral to the alternator itself) to control the output but it functioned the same way - lowering or raising field voltage as needed to control output.

Now, the C7's computer controlled alternator is no doubt more precise and can vary the field voltage in many more "steps" to more precisely control the alternator's output but the underlying principle is exactly the same as the old electro-mechanical ones

I only took exception to the claim that made it sound as if controlled output alternators were somehow new to the C7 when, in fact, they've been around since generators/alternators were first fitted to vehicles

Last edited by KenHorse; 03-24-2019 at 02:12 PM.
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Old 03-24-2019, 02:58 PM
  #29  
JerryU
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^^
It's only the step voltage drop I (and others) have seen that was a concern. The old systems moved slowing in the same direction as you said. Like oil pressure this system will rapidly go from around 14 to 13 volts or even the high 12's.

Last edited by JerryU; 03-24-2019 at 03:00 PM.
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