spearfish25

I picked up my C7Z 3 weeks ago. No issues. Now I got home from a 4 day trip and the car wouldn't start. Had to jump it with a mini portable jumper. I had everything off so what gives? Just a bad battery?

Frodo

I'd say its likely a bad battery. I've left mine undriven and without a battery tender for a month without problems. Do you have any gadgets plugged into the OBDII port? They can drain a battery though not likely in such a short time.

JerryU

The 2014 Service Manual shows you can typically go ~30 days with an 80% charged battery and still start the car. If a device like a V4 defeat is plugged into the OBDII port it could drain the battery much more quickly. Folks have reported that device doing just that. I have tried to find out what current draw my Window Valet has but so far the manufacturer has not responded!

Note, from info in the 2014 Service Manual a 750 milliamp current draw can reduce the time to a day! Even with the low voltage (~12.4) I have in my battery from day 1 (probably a week cell) I have been on vacation several times for 2 1/2 weeks and no problem starting. I don't use a charger. However because of the low voltage and the fact that my battery will be 3 years old in October, plan to replace it with a higher capacity AGM battery before winter.




If fully charged car should start after 30 to 35 days

spearfish25

Thanks guys. I do have a Dashboss plugged in but that's never killed a battery on any of my previous cars. Voltage reads high around 15.1 while driving so I'm suspicious it's a battery issue.

I may start unplugging the Dashboss if I'm not driving the car frequently though. Wish it had an auto shutdown.

JerryU

Thanks. I have an M7 so no issues with needing a V4 defeat device. Would be good to have the mfg of those devices indicate what the current draw is when the car is parked. Can't believe it is anywhere near an amp. 1 amp at 12 volts is 12 watts. That generates a good deal of heat that would have to be dissipated! Like holding on to a 12 watt bulb, won't do that very long!

Not sure why I have not had an answer for my Window Valet-it's certainly not proprietary as it could be measured!

Keep us posted on what you find.

lakemg

Same Dashboss used on previous cars you owned or a different unit? I'd fully charge the battery, remove the Dashboss, and let her sit for 4 or 5 days and see if the battery stays charged so that you can determine true root cause.

JerryU

Sent another email and the President of Top Down Technologies answered and apologized as he thought they had answered my question! Perhaps he had, I found the reply in my spam!

He said they worked hard to reduce the current draw for the C7 and believes they achieved under 0.1 milliamp. He thought 0.05 milliamps. Since the battery load when parked is about 30 to 35 milliamps (see my post #3 ), the addition of 0.1 is a non issue!
He also said after the car's bus activity ceases, the Window Valet completely shuts down its clock and the processor stops. It re-starts when there's activity on the bus again. I assume when you press a FOB button it activates the buss. No fear of it affecting battery life.

spearfish25

It's the same Dashboss that I had on previous cars. I did update the firmware recently which is the only difference. I'll unplug it the next time I'm parking the car for a week and see what happens. My mini portable jumper is the best $90 I've spent. Keep it in the car for jumps, random phone charging needs and it also powers my DC quickjack. So I'm ok regardless.

rmorin1249

I had the exact same thing happen to me. I drove to and from Bowling Green for the Bash from Maryland. Parked the car when I got home and the battery was completely dead the next morning. The only external device I have in my car is an ipod Touch. Dealer charged the battery overnight and said it passed all tests. I am now using my CTEK whenever I park the car overnight. Seems like overkill but I'm paranoid. Called GM and was told that unless you have something plugged into the rear charging port everything else should power down within a few minutes of shutting down the engine and locking the car. Was told that even if you leave your lights on, door open, etc. the car should turn everything off. Still wondering what caused my battery to go completely dead in less than 24 hours.

Boiler_81

Putting the car on the charger every night is a band aid. Modern vehicle electrical architectures are designed to minimize the key off load. If the battery drains overnight, there is an issue with the battery or the electrical system. If it were my car, I would let it set several days off of the charger to make sure the dealer was correct with their diagnosis. If it drains, the dealer should repair it under warranty.