Thanks, Donbrew. I read on here about the problems that come with disconnecting the module. Pulling the fuse is ok, I hope. I know the bluetooth features won't work but they mean nothing to me either, just like onstar and XM radio.
I started the car and played the radio, no warning lights came on, wasn't watching the scrolling badnews billboard, though.

 

If I put one in, it's getting a Delco. Since buying one I have done a lot of catching up with the tech in these things. As a result I think the battery in the HHR is a priority for its reliability and good operation.
A weak battery, in this car, could give some good headache.

 

I was right there is a TSB for 2009 OnStar units sucking the battery. TSB# 09-08-46-004a
All the way at the end of page 12 https://www.chevyhhr.net/forums/prob...-23231/page12/

 

This forum is great, and Donbrew is one reason why! I saved the relevant text on a .doc on here.
Thanks a million, DB. I'd bet a dollar that's what it is. I'll know in a few days since I pulled the fuse. It'll take a while to see the difference. Or I could get out there and check its shut off current draw.
Waiting is easier!
ha

 

I've learned something that HHR newbs might find interesting. I have a voltage meter (it's accurate, I checked) that gets plugged into the power socket and reads out the actual voltage on the line. The HHR's power control programming controls the alternator's output.
If your battery isn't fully charged, it raises the field voltage sent to the alternator. This will raise the output voltage accordingly. I was seeing voltages as high as 15.1 (momentarily) on a freeway drive this evening. After 25 miles I got to the destination, coming back I noticed the voltage tapering as it became better charged, when I pulled into the driveway the voltage was 14.6. A little more like I would expect.
This is one smart little car. This thing has some spooky tech in it.
I like it!

 

That's no great surprise - that's the way charging systems have worked for years.

 

New to me. My last car was a '93. It charged at 13.XX volts.

 

I was reading through the HHR service manual a while back. I remember the specs saying that the upper limit charging voltage could be as high as 19 volts.
I was kind of surprised by that.

 

Lots of people are stuck in the days of a black box that clicks being the regulator. They controlled the output of the generator, now the computer controls the field duty cycle to control how much electricity is produced (current).

BTW, that is why that plastic ring around the negative battery cable is very important; it's the current sensor.

You have to think of the alternator as a motor in reverse. It won't work without a good battery. Some alternator designs include a generator to make the field current so the alternator can function without a battery.

 

I have some new info that those curious might be interested in.
I started the battery charging at 2 amps at 1:30am and raised it to 6 amps at 2:30 this afternoon, then took it off at 4:00. The battery had a surface charge of 13.2 so I turned on the headlights to burn that off. At 12.7 volts I took off the neg battery cable and put a good meter in between the post and cable. On first connection the load was 1.7 Amps for about 1 minute, then drops right to 85 milliamps. This was with the Onstar and Interior lights fuses pulled.
This would have been a little high on my '93 merc but is to be expected on the HHR, so my troubles are basically a slightly weak Duralast (autozone) battery and too many short hops.

Stock '09 LS, no OnStar or Dome lights the constant draw is 85 ma.
Which seems fine to me.
I think KOI sells Ac/Delco batteries around here.