Mikec7z

(Edit: I'll leave this first post below, unaltered, but as the thread progressed, we got to the more realistic problem that the 48v system that runs the car's computer network, if it is low on battery, it may not let the car start as it may have ultimate control of the ignition and theft deterrent etc, and having the 12v system charged, does no good if the 48v system is low or dead)

By no means am I an electrical genius, but just wanted to try to bring a new angle to this, and feel welcome to shoot me down... but lets jump into it....

My gut says that there is something going on here that has to do with when the cars utilize the electric assist. I believe the cars that have the electric assist are the same cars that are not starting and dying at gas stations.

Here is my thought... lets say you are GM and you have this new vette, and you put electic assist in it... and so people are out driving the car around, testing it.

And they realize, okay, im getting low on gasoline, but thats okay, because I have an electric assist engine in my car, it can keep me going.
So they use the electric to get to the gas station, and are almost out of charge...

and that's when trouble strikes...

after putting gasoline in their car, the cars "electrical system" perhaps equalizes charge across its batteries, and therefore, they are ALL dead at that point... OR, more realistically, the 48V battery is on a seperate loop from the electric assist, BUT, the 48 volt loop that runs all the accessories when the engine is OFF... it is dead by the time the car has fuel and is going to be started again.

And the engineers did not realize that people would run out of gasoline, and keep driving the car around in electrical assist mode.... or maybe even with gasoline, the engine does not get fired back up in time, and the electrical assist mode drains the 48v battery as it runs the accessories.

So how does one start the car if the battery is dead?

Jump it of course! Duh...

Oh, but that's right... we are running 48 volts now... the 12v batteries i hook up to for a jump dont do anything for me do they? ahhh, darn! Tow truck time.

But since we are chevy engineers, we are still going to try to jump it and show that our intentions are to work hard and be smart problem solvers!

(seriously, if you guys are impressed with a chevy engineer who thinks a 12v battery is going to jump the 48v battery in the vette, go ahead and go play in traffic now and see if you can get them to go with you We can hire some more, they might even be smarter, it will be a tough chore, but we will manage)

I could keep typing, but i think thats the end of the story, at least for that idea. Could it be something else? sure... but i just wanted to throw this idea out there, because this COULD be the problem.

range96

I think you're all wet on this one. Running out of fuel/battery charge will NOT cause a delay in the C8 schedule. Especially, even according to your guess, not all cars will have the electric assist. Sorry!

Mikec7z

keep in mind, i did mention, not running out of fuel, but just keeping the car in EV mode as much as possible, could put too much dependence on the 48v battery to run accessories... and then when a person needs to bring the gasoline motor back online, theres not enough juice to make that happen.

Also keep in mind, you can SAY GM would not need to worry about people running out of fuel or charge... but a normal car does not strand you after you do, you add gasoline or jump it and away you go. This vette, you would most likely be dead in the water after your 48v battery is too low to start the car

And since all cars are automatic, you cant use the EV batteries to pull/jump start the gasoline motor

And you can still say GM would not need to worry about it, its the customer's problem...

but when GM offers free road side assistance or sell it as a package in the finance office, FOR THEIR FIRST YEAR MODEL VEHICLE (people buy these packages you know) and all the sudden vette owners are all each calling tow trucks once a month, GM is in the red in a hurry.

Roadside assistance covers dead batteries and out of gasoline btw

So as a test driver, you have to act as an illogical human, and intentionally do what a stupid driver would do, and then see how f***ed you are with a dead battery after acting like 90% of the population will behave.

I also understand not all the cars have the electric assist... but keep in mind, not all the cars have been breaking down.

And it seems to me, the cars the nerdy employees who would study EV characteristics, are the ones who keep breaking down.

The black lady engineer in the last break down does not strike me as a high speed vehicle tester... i could be wrong, she might be a better driver than I am... but i just don't see it.

The fact that they keep trying to jump with 12v cars, is driving me crazy though to say the least. It would be one thing if they got it started... but at this point... you know its not going to work... i would hope... yet they keep trying

But lets say the electric assist is not part of it, and it is all the can bus stuff, you are still always going to be dead in the water with a 48v system that gets too low on charge to start the car. So, there is the main hurdle right there... you cant jump the damn car.

23/C8Z

The current electrical system can bus has a hard time doing what it's supposed to now. Tack on another 90 modules communicating. What could go wrong? Maybe they hope you don't drive the car long enough for it to happen. Like rebooting a phone or computer lol.

Mikec7z

makes sense too, but i would think disconnecting the battery and connecting it again, and jumping it... would solve it...

but again, i dont think these cars are going to be able to be jumped easily

Mikec7z

my gut is, we are running into a case where, no one with solid common sense called out the nerds, and GM is in trouble right now.

And im calling it a night, see you folks tomorrow where we debate the IQ levels of people who DONT have a power inverter device that takes 120v ac to 48 v dc, so that when they do try to jump the car, they have a gizmo in the middle of the jumper cable circuit to boost the voltage to 48 from 120ac that plugs in a wall. Genuine corvette accessory, only $599.99

Engineers should have bought them from the parts department before they took off for their daily tests

Or better yet... million dollar c8 prototype... but a 48V jump box kept in the trunk, is just not a wise investment. Tow trucks are cheaper and so is the bad publicity

I only tease because I know GM watches me like a hawk Trying to help them learn some really profound stuff right now.


https://www.corvetteforum.com/forums...-399-99-a.html

ShagVette

BIG Dave

No electrical engineer is going to try to jump a 48V vehicle with a 12v battery. It simply makes no sense to think 25% of the required voltage is enough.

MAD IN NC

Future phone call..... GM Service Mgr. “System freaked out and quit when ya opened the door wo turning car off. Need to be towed to dealer to reset. OOW charge $495 + tow.

Didn’t you read the manual? We do this because we used C7 taillights and they will suck all power off 48v plane”

Red67John

I suspect the electrical issue is simply related to the new Global B CAN system as has been widely reported as the issue. Beyond that there is way too much Corvette Forum speculation. Hell, it could just be that the wiring harness was designed for round taillights, and we’ve see how that won’t work.

roadbike56

CFOT called. They want to remind you that all C7 taillight hate posts must be approved by Knooger and K-spaz. Please refrain from further posts that do not have their approval.

MAD IN NC

approved by SteveR. LOL

84 4+3

Last I checked, well the only one I ever saw really, the 48v system ran the accessories and there was a separate 12v system just for starting and a couple other small loads... it would be stupid to say the least that one would use the hybrid battery to also start the engine and anyone with half a brain cell would see that while doing a lay out. The problem they are having right now is in my expert opinion (if it is even real) a module communication issue related to the can bus. Just my speculation though.

*C7*

I'll vote for this one.

vetteLT193

This. Period. Global B has been widely reported since early 2015. GM has jobs posted hiring for engineers for it. The OP has taken the least logical stab at the electrical issue.

vndkshn

I think OP's other post about being a forum vendor and selling 48v jump boxes highlights he is not aware of this.

oregonsharkman

As an Electrical Engineer for avionics systems, I highly doubt that the engineers screwed up any basic system level power analysis. The most likely scenario is that there is an issue with the electronics logic either in firmware (Hardware Description Language used in a system controller FPGA) or in the software. Deterministic analysis of every state machine scenario is not possible in the very complex systems used in current automotive design, so they rely on simulation, test-bench verification and subassembly hardware test.

Remember - NOW is the time they are SUPPOSED to find these issues. There is nothing out of the ordinary going on with the C8 electrical development - just a late development stage verification finding. This happens all day every day in avionics.

84 4+3

Is that why 737s are falling out of the sky? (Kidding of course)

oregonsharkman

All kidding aside, it might be....It appears to be a flight system software function that overrides manual controls unless it is switched off.

Mikec7z

so assuming everyone is correct that there is a 12v and a 48v system... does the 48v system have its own battery also, or no?

is it possible that the 48v system is what is going dead and not the 12v battery?