ElmScan 5 and phantom power draw.

I've been having weak battery problems. After a few days of sitting, the battery would be down/dead. Eventually the repeated drains killed the stock battery, so I put in a new one. Of course, that just delayed the problem until it could run down, but at least now I was watching for it.

 

I did some current draw tests tonight:

Car and computer off: 110-120ma, some bumps to 240ma.

Disconnect my car computer: 70ma.

Disconnect the ElmScan 5: 30ma. (Which I think is stock power draw)

 

So the ElmScan 5 is taking 40ma of current when the car and computer is off, which more than doubles the power draw of the stock car.

 

The car computer draw I expected- I had measured it before. Even in full shut-down, the Carnetix P2140 takes 45ma or so. I may put in a hard switch so I can turn it off completely if I'm not driving the car.

 

The ElmScan will be tougher- I'm thinking of putting a relay on the 5v USB power line from the computer that will break whatever power signal it's getting from the car. Not hard to do, but a pain to tear it out and modify it.

 

So, heads-up. Don't leave your ElmScan plugged in all the time, unless you can deal with the doubled current draw.

 

Now in theory that 40ma draw would take well over 60 days to fully deplete the battery, so that probably is not my only problem, but it's the one I found tonight. : )

 

Next up I need to figure out if I'm getting higher pumps in power occasionally. I saw some evidence of that (saw 240ma once for no reason), but did not track it down. Maybe the computer is waking up once in a while to look around...

That Carnetix draw seems a bit high. The Opus PSU I am about to use is rated at 3ma standby draw plus whatever the motherboard is using.