[high_climber]

You guys are the best. Thank you for all the insight and sharing your wisdom on the matter as always. As for mods the only other remaining mods after returning the reverse lights to OEM are LED plate lights, skip shift eliminator and a mishimoto catch can.

I’ll watch the voltmeter carefully and see if I can learn a bit about what’s happening between any discharge, the alternator, and the tender’s relationship with the battery charge. Besides this one problem and a cylinder head that was leaking coolant in its first month the car has been a dream! Will keep you guys posted with voltmeter data and any new trends that develop.
I had wondered if the dang onstar that emails tire pressure and OBD info was the culprit also

[TJay74]

You cant watch the alternator as they dont operate like the older style ones did. GM uses a computer controlled charging system and alternator on the vehicles now, at times the alternator will not charge in order to reduce load on the engine for fuel mileage and to allow the battery voltage to drop down some in order to get a better charge.

The Camaro battery is a AGM battery, most battery chargers will not charge an AGM if it is under 6v. If the battery is flat dead you have to get it back over 6v before you can put one of the newer smart chargers on it. Make sure to charge it on AGM mode as well.

If it keeps happening have the dealer open a case with the GM TAC line, if they cant sort it out there will send a GM Engineer out to dig into it further. I cant remember if it was a Camaro or a GM truck but a member had the same issue, ended up being one of the modules in the seat system was staying awake causing the drain.

[Aragorn]

Originally Posted by Nsxmatt

There is nothing for service to look at. There are many threads here and was found that the onstar unit is sending out and receiving info several times a day. The proximity system for the keys must also always remain active to detect a key. New cars with wifi and keyless systems all brands drain. We have a designated person that charges cars every morning on the lot for that very problem.

Is it possible to disable OnStar?

[Glen e]

I refuse to believe that onstar is the culprit. GM engineering can’t put a car on the road that kills the batt after a week or two.....it has to be something else

[Nsxmatt]

Originally Posted by Glen e

I refuse to believe that onstar is the culprit. GM engineering can’t put a car on the road that kills the batt after a week or two.....it has to be something else

I mean, you don't have to believe and you can beat yourself up trying to figure it out but it's most likely the culprit. My car sends me an email if the tire is low, oil needs changed, many things. How do you think it gets it's power to sit there and constantly check the systems? The commands you send from the phone app.. something has to be on constantly to receive the signal. The proximity keys... how does the car know you are near? It HAS to be on constantly. These cars are made that way, not just chevy it's all cars. Some draw more just sitting and some don't and can sit longer. In any case not driving a car a week or two is not normal operating conditions. So having a tender is needed. It's just the way it is.

[ctrlz]

Originally Posted by Glen e

I refuse to believe that onstar is the culprit.

I agree with Glen. It is very unlikely OnStar would draw enough current to kill a battery that fast. All modern cars have computers running all the time, even when "off." These are milliamp loads.

As far as Tjay's comment... I would hope the smart charging system would prioritize recharging the battery over reducing engine load, otherwise not such a smart system.

[Nsxmatt]

Originally Posted by ctrlz

I agree with Glen. It is very unlikely OnStar would draw enough current to kill a battery that fast. All modern cars have computers running all the time, even when "off." These are milliamp loads.

So a car communicating with all it's vital sensors and to a satellite multiple times a day over the course of two weeks is only a "milliamp" load?

[hotlap]

Both times my battery went dead I could hear something running at the very front of the car. I think it was on the right.

I noticed it when I was taking my dog's out before bed but didn't get concerned enough to jack up the car and track it down. It was late and I didn't expect the dead battery.

After the second time, with the LEDs removed and the dealer saying no problem. ...I vowed that I would jack up the car and track down the running item. It didn't happen again in the following 6 months I owned it.

My theory is that cars have CAN electronic control system that is like a "nervous system, enabling communication between all parts of the body". Literally, signals for multiple related and unrelated items travel on the same bus. Does a simple change, like a LED light, create a conflict that causes something else to run.

GM tests the car as a system. Aftermarket suppliers are not validating their parts on that system.

For what its worth

Edit: mine was (is) a daily driver so time between starts was less than ~12 hours

[Glen e]

NO car Made these days would get out of the engineering section if it killed the battery in two weeks. It wouldn't pass what we called at BMW "the airport test". Meaning that the battery would be dead when you came back from a business trip for three weeks. Sure , it would kill the battery within months, but not two weeks. It's something else.

[Nsxmatt]

Originally Posted by Glen e

NO car Made these days would get out of the engineering section if it killed the battery in two weeks. It wouldn't pass what we called at BMW "the airport test". Meaning that the battery would be dead when you came back from a business trip for three weeks. Sure , it would kill the battery within months, but not two weeks. It's something else.

Um I worked for BMW for a few years. BMW requires showroom cars not driven over a week to be placed on a charger once a week because they lose charge. At Honda now they require tests to be run on every lot car once a month. The cars have a constant draw and will kill batteries. If we don't test and charge them Honda denies a battery claim and sales pays for it.

It is a common new car problem now.

[Aragorn]

Cars on battery chargers? I’m sure it’s a real issue, but had not heard of it.. crazy.

[CoolbreezeNJ]

This is what you have to do. Remove battery terminal and put a 12V test light in series with it. Then you start going and pull fuses. Continue pulling fuses until the light goes out . If not try and find connectors to accessories and pull them also. You will eventually find your drain and that is the problem circuit. Where it gets complicated is should that circuit be on all the time and I doubt any of the systems say Onstar are on all the time for obvious reasons. Likely they are woken up in intervals. I suspect you will find the accessory or problem circuit that isn't being cycled. This worked 40 years ago and it will work now yet it is further complicated by these newer systems.


As it regards the alternator put a voltmeter across the battery terminals. My car often reads low and I guess it is due to the computer controlled regulator. Being that is the case start putting accessories on in the car, watch the voltmeter and also watch the meter inside of the car and find the corresponding measurements. Start with head lights then heaters then seat heaters defrosters , etc. Heating elements are the biggest draw besides the head lights. Now you can see how the car is charging or if it is charging correctly. Putting a big load on the alternator will make it work and if it doesn't then the alternator is bad. In the past I had a BMW that had a bad regulator and un-believable you could change the regulator as it wasn't internal to the alternator itself as so many units used to be.

[Mountain]

Originally Posted by Glen e

I refuse to believe that onstar is the culprit. GM engineering can’t put a car on the road that kills the batt after a week or two.....it has to be something else

No? I wouldn't toss the possibility.



Point of thought: A car keeps throwing a code related to the charging system, that ultimately ends up disabling certain features on the car. Thorough diagnostics indicates the entire power and charging system is working A-1, 100%. Can't find anything wrong....

After significant time monitoring various circuits, it is noticed that there is some "extra" power on a circuit that wasn't originally designed to be there. Come to find, some engineering team made a design change, there was a mix-up/fault in communication with engineering teams, and this was not accounted for with the circuit design/power distribution and malfunction code logic. Ooops.

Of course, none of this was present in the prototype vehicles as the change was made late.

(This is based on a true story)


Anyway, my 2016 SS I could leave for at least 2 weeks before it was hard to start (I think I left it once for 3 weeks). My 2017 SS 1LE, I can't leave undriven/not on a battery tender for more than maybe 10 days or it won't even start. Not my biggest concern right now, but I am looking into this.

[Mountain]

This information is from the GM service information. I will summarize a bit.

-Aftermarket accessories installed into the courtesy lamp circuit can cause the inadvertent power timer in the BCM to keep resetting; causing the BCM to remain awake.

-OnStar Generation 6 and later does not wake up every 10 min for the first 48 hours like the Generation 5 and prior. The Generation 6 and later version's current draw is less than 40 mA. The OnStar system is left in that state for up to the 48 hours. Parasitic draw of up to 40 mA with an occasional spike as high as 80 mA for the first 48 hours is normal. (6th Gen Camaro uses Generation 10)

->Generation 10 has a 4 day "stand-by" mode on none-subscribed vehicles and 10 days with subscribed vehicles. In this "stand-by" mode, OnStar can draw 1-3mA. (with that said, I feel like this is worth bringing up: https://www.consumerreports.org/cars...-to-customers/)

-Some automatic climate control systems can remain in a semi-awake state for up to 3 hours and can be up to 50 mA.

-There is a low (mA) current level consumed by the remote keyless entry receiver for monitoring purposes while not awake. When a device on the same remote keyless entry operating frequency are activated, such as the TPMS or FOBs in the vicinity, the remote keyless entry receiver will then wake up.

-Parasitic drain can be up to 80mA at times.

-Transport Mode is "designed to help vehicles that are not being used (In Transport or Storage) use less battery energy. Vehicles with this feature are generally shipped from assembly with this mode on. While in inventory we recommend that this feature be on."

-"The Transport Mode feature when enabled reduces the parasitic electrical load on the battery when the vehicle is parked, which extends the battery stand time up to 70 days without the battery going dead." (up to 70 days, but not necessarily 70 days)

-Transportation Mode "should be left On while the vehicle is in dealer inventory. Also a customer may want to use the mode if the vehicle is going to be stored."