odysseys will charge fine with a standard charger from Chevrolet… I used to sell Odyssey for marine applications. Great batteries.

 

Thanks! I will use the factory trickle charger. I just took a good look at the oem Chevy trickle charger manual. Apologies for not looking there first. It appears to be a CTek and the manual says its good for all Lead Acid (Wet, EFB, Ca/Ca, AGM and Gel) and 4 Cell Lithium (Li-FePO4, Li-Fe, Li-iron, LFP).

 

Hmm, it's NOT the battery "dropping voltage." It's the computer controlling the battery charging that you are seeing on the gauge! Days of "solenoid actived" voltage regulators are over. Like everything in the C8 a computer chip is in control.

As I stated in Post #39, in most driving conditions The car is in what they call:
Fuel Economy Mode
In Fuel Economy Mode targeted generator output voltage is the open circuit voltage of the battery and can be between 12.5 and 13.1 V. That will happen when the battery voltage is over 80% as it saves LT2 energy to NOT charge past. 80% is all that is needed and charging higher uses more engine power than needed.

It will switch to Charge Mode under some conditions OR IF the battery drops below 80% charge that computer chip using the GM algorithm will increase the alternator output voltage to a charging voltage and will show between 13.9 and 15.5 V.

SIDEBAR
My E-Ray has Stop/Start. So with a fully charged battery the gauge called battery (which is actually the alternator output as is your gauge) might read as high as 13.5 volts. That is supplying whatever power needed for fans, AC, sound system etc. I replaced the OEM battery with and AGM battery in my 2014 C7. Worked fine.

When at a Red Light and the engine shuts off the gauge (now reading ONLY battery voltage) will be 13.3 volts. If at a very long light it may drop to 13.2 volts as the battery has been supply power for fans, AC, sound system. When engine starts it goes to 13.4 to 13.5 volts for a short distance as than drops to 13.3 volts, the max GM elects to charge the Li-Ion battery. You can shut off your engine, press start without foot on brake and read battery voltage whenever you'd like.

PS: The GM Maintenance charger GM sells, and has since 2020 can maintain a Lead Acid, AGM OR Li-Ion battery. That is what I have for my E-Ray.
SIDEBAR:
However I seldom use the GM charger. I drive every week at least a few times into town, ~60 miles round trip. Enough to keep it fully charged. In fact with my two C7's and my 2020 C8 was on vacation for 3 weeks and did NOT use the charger. No need, started fine. My concern in NE SC we have many thunderstorms late in the day in summer. Have lost 3 sprinkler controls, a garage door opener and lights that are on the garage power line. Do not want to risk my car! Plus no need.
Going on a cruise and will not use it on the E-Ray where it's Li-Ion battery can probably go a couple of months and still start the car fine.

 

Thanks for the clarification. I did read your previous post about Fuel Economy Mode etc. and found it very informative.

I installed the Battery Tracker Plus from AntiGravity Batteries about 50 miles ago. Since then I have used the Chevy/CTEK Trickle charger twice on different nights while parked in the garage and the SOC was 100%. The Cranking voltage was reported to be low at 9.49v. I initially figured it to be an anomaly and intended to wait a few weeks before acting on it to see now it would go. However since the State of Charge was reported at 100% (CTEK disconnected), I decided to listen to the radio and change some settings on the EQ and other parameters. This was only a 15 minute listen at varying volumes admittedly very high at times but never at distortion levels. I shut the car off and opened the Battery Tracker Plus to see a 56% State of Charge. I have never seen anything like this before and decided to upgrade to the Odyssey. I read too many horror stories about low or dead batteries causing all kinds of problems in the C8. For $300 I figure I would give it a try. I do realize the computer will ultimately decide my SOC. The Bose AMP surely draws a lot of juice so perhaps the Oydessy AGM will keep up a bit better.

 

Interesting. Yep I always have my Bose 14 speakers on pretty loud 98% of the time. In my E-Ray where I use Stop/Start the dash gauge reads only battery voltage when stopped. It drops from the max the alternator charges, 13.3 volts (~85% capacity) quickly to 13.2 volts. When I start moving (if it doesn't start the LT2 sooner) it jumps as high as 13.5. Within a ~mile it's back to 13.3 meaning the Computer is happy with that charge level!

 

^^^
Interesting. Yep I always have my Bose 14 speakers on pretty loud 98% of the time. In my E-Ray where I use Stop/Start the dash gauge reads only battery voltage when stopped. It drops from the max the alternator charges, 13.3 volts (~85% capacity) quickly to 13.2 volts. When I start moving (if it doesn't start the LT2 sooner) it jumps as high as 13.5. Within a ~mile it's back to 13.3 meaning the Computer is happy with that charge level!

 

Does the ERay Traction battery ever charge the 12V starter battery? I owned an EV where this occurred frequently and a light came on to indicate it had started.

 

This according to a tech-link article:
"The 12V lithium-ion battery is charged by the K1 14V Power
Module while the vehicle is operating in the EV modes (Stealth
and Shuttle modes). Once the vehicle exits an EV mode and the
engine is powering the vehicle, the generator takes over 12V LiB
charging."

https://gm-techlink.com/wp-content/u...April_2024.pdf

 

Yep as Andy says when in Stealth mode. Seems crazy as can't run in Stealth mode for more than a few minutes. But it includes a DC to DC Converter to do just that. All other times the alternator charges just like a standard C8. Many Hybrids don't have an alternator. In our 2025 BMW X5 SUV hybrid would be useless as we go several months and NEVER start the engine.

My GUESS is the Converter is there because GM planned on a high mpg version of the E-Ray when they started the design in 2012/2013! Like Ferrari who did the same BOTH introduced Performance Hybrids then when a "government dictated" higher mpg they would use the forced Stop/Start software and start always on battery until the car reached ~45 mph. They would use different types of batteries. Need not be bigger as Toyota had a Hybrid that achieved ~50 MPGe with a 1.3 kWh battery smaller than the E-Ray 1.9 kWh! BUT would not be a fast charge/fast discharge! We may see it yet! But perhaps not as with GM staying on their Plan of all EVs by 2035 my "GUESS" is we'll see an EV Vette that does 0 to 60 in <1.9 seconds before 2030!

 

I wonder what state of charge it targets when it is being charged by the high voltage battery system? I assume that when the car transitions from Stealth to ICE, it happens on the fly in a seamless way? If the normal computer controlled charging system targets 80%, then when its shut off its only 80%, and decays down from there. The pre-charge from the high voltage battery system in stealth mode might just be to insure that when the transition to ICE occurs, it really is seamless, smooth, and fast. That would be no time to find out your starting motor battery was low.

I also wonder if alternator based charging system for E-ray is the same or similar, targeting 80% SOC. We know it uses a different battery monitor module that is actually built in to the LI battery, rather than the external battery monitor in the Stingray. But is the algorithm different? I don't have a service manual description that covers the Eray. I think you measured voltages didn't you?

 

Those are some of the questions up in the air.

As far as Stealth Mode, it's a joke IMO! I can't get to the end of our 2-mile rural road to the highway at our speed limit of 25 mph! 1st a bit of a PIA to even use. Have to have belt buckled and wait for three Pics to appears in the dash. Then rotate to Stealth. Don't know anything is happening until you press the accelerator. Then our road has a number of turns, a few close to 90 degrees as it goes around "finger water paths" in our Lake. IF going say just 30 mph when you turn it speed scrubs. Press the accelerator ~20% to maintain speed and the ICE comes on instantly. Can't go back unless you, stop the car, go thru the ritual of selecting from the three pics etc. So hard to understand why they have the charge from EV battery complexity. I never use it so that Converter not used.

I expect the lower charge voltage the computer-controlled alternator provides, which is the same as the GM Charger I have, 13.3 volts. What is the reason that is Max?

• First it does increase battery life, all Internet info says that is the case.
• It is less stress on the battery. Like Jason Fenske's video on Li-Ion car batteries where he said it's like filling a parking garage, easy to find places if 80% full. Tough as it gets closer to 100%. His statement it takes more energy as you charge higher.
• That taking extra energy also means it's using more ICE power so like lead Acid Batteries where GM (and most modern cars) only charges to 80% it makes the system slightly more efficient.

BUT my guess GM does not say.

 

In stealth mode what accessories are functional? As you recall, with the Stingray, with car systems fully powered up, but headlamps, tail lamps off, I measured 10 amps of draw engine not running. With headlamps on, tail lamps, maybe heated seats?, other accessories, the draw could be considerably more. So, the connection between the high voltage battery system and the 12 volt system would not just be to "charge" the battery, it would also be to power the car systems and accessories in stealth mode. But it does sound like a bit of complexity for the limited added value of a stealth mode. I wonder how much it adds to the price of the car for that mode to function.

Edit: from the manual it looks like climate control is off during stealth - says turning on climate control deactivates the stealth mode. But I assume lighting system work?

 

^^^
Yep no climate control in Stealth. Heck that would be a show stopper in my wife's BMW Hybrid! It uses EV battery power for AC and heat. In fact if you program when you will typically drive it will start say the AC or Electric heat a half hour before. Found that out and was in a panic as we are on Time of Use power and the silly car was using electric in high cost power rates.

For example we are only paying $0.053 kWh of what is called Discount Rate. Actually with the solar and Nuclear power Duke has that 10 hours a day. Our Peak demand rate is $0.17 kWh. Called what they call BMW Genius and said I have a Catch 22. Can't set time I want charging unless I 1st set typical drive start time. Recall he said yep that is so it can condition the car when your plugged in! I tried to explain can't do that.

I then found the answer on the BMW Forum. Something I used when we first started on Time of Use Rates in ~1986. Put the electric Hot Water heater on a timer (now have a natural gas Rinnai for hot water.) So that is how I have the car set now. Can plug the car in anytime BUT the power is only active when the timer I installed allows! But it is amazing, they must have strip heats by the Vents as instant heat when you get in in the winter. Cools quickly as well. Not sure how it cools! But as I said we may go a month or more and never start the engine. Now on a full charge we're showing 52/53 mile range. In the winter is was somewhat less, assume it calculates power for heating!

 

https://www.corvetteforum.com/forums...y-charger.html

Is this why it took so long to reach 100%

Will the CTEK do this? Does this charger maintain, float and condition as well as charge.

 

Sure my 2025 GM charger made with their name by CTEK does that for my E-Ray. Since 2020 the GM charge does both Lead Acid, AGM and Li-Ion batteries.

My 2014 CTEK similar to GM's does that as well only for Lead Acid (& my AGM) batteries. Seldom used on my Vettes. No need as drive several time/week. Went on vacation for 3 weeks with my two C7s (a 2014 and 2017) as well as my 2020 C8 and DID NOT use the charger. No need, started fine when I returned (as GM says it should.)

When my Street Rod maintenance charger broke I mounted it on my Street Rod. It's on 24/7. I watch as it maintains my Yellow Top Optima AGM battery!

 

Obviously isn't affecting your charging, but the CTEK manual actually says to use the higher level (snowflake) to charge AGMs

 

There is no snowflake setting. The manual that comes with the CTEK model supplied with the C8 indicates it is suitable for FLA, AGM, and several types of LI batteries. It does not require any settings to do that.

 

At 5 years the OEM battery is getting close to failing. When you remove the battery you will see it has a 42 month Full Replacement warranty label. But the actual warranty is just the 36/36,000 B2B warranty, if I understand it correctly. In any case you are past 42 months.

I always buy batteries at Costco. 36 month full replacement Interstate batteries. Bought one last week for my 2022 C8, $133. You can replace it for free every 35 months if you want. No questions asked. I don't do that but I have heard of others that do.

BTW back in 1978 I replaced the battery in my 1970 Mercedes and noticed it was 8 years old and came new with the car. Don't think they would last that long anymore.

 

I was referring to his CTEK 3300 charging his street rod.

 

IMO IF you need max capacity probably a good idea. But I have had my Street Rod now 25 years old on Optima Batteries it's whole life. Built the interior battery box with a clamp that fits around the round cells! Prior chargers did not have slightly higher AMG voltage. One lasted 9 years and only changed it as SR has no door handles only electric doors and windows. Battery goes at a Show with door shut SOL (well without breaking a window to jump start as battery inside the car. I do have a way but PIA!)

Feel about the same with GM only charging the Li-Ion 12 volt battery to 13.3 volts about 85%. Yep like my friends with RV's and multiple Li-Ion batteries, that want max capacity, so when parked at night, engine off they get max usage. Heck with life or saving energy!


BTW my 2025 GM charger which says for Lead Acid, AGM and Li-Ion has no optional setting. Just plug it in regardless of battery type.