FU: PSA: OBD II dongles draw power when the vehicle is off.

[Tofer]

I'm going to guess that the WiFi dongle you got draws more power than you'd think because it is WiFi.

[RAMd®d]

According to the spec listed at Amazon, that dongle uses .75W or 62.5ma (at 12VDC).

That's higher than I'd like for long term use. If the battery isn't in really good shape and the weather is cold, I can see this killing the battery off, at least enough to keep from starting a car.

And that dongle isn't really designed for long term use. Plug it in, do you what you need to do, unplug it. It may not be convenient, but neither is a dead battery.

[davester]

Catzilla wrote:
The battery is a little over two years old, but this car eats batteries.

Cars as a rule don't eat batteries, usage patterns do. For example, if you drive the car only short distances between starts, then the battery doesn't get a chance to recover to full charge because turning the starter motor is a vastly greater load than anything else in the car. Sitting at partial charge is very bad for a battery and is the main thing that will shorten its lifetime. Also, if you accidentally run a battery flat a couple of times you can pretty much kiss that battery goodbye.

[M A V I C]

I found that, depending on what I'm doing, I need to turn the car off, on then off again after I disconnect my app. Otherwise the ECUs don't completely shutdown when the car is off after certain tasks are run. So it's not the OBDII adapter that does the drain, but the car's ECUs after you've fiddled with them.

[Pat]

davester wrote:
Cars as a rule don't eat batteries, usage patterns do. For example, if you drive the car only short distances between starts, then the battery doesn't get a chance to recover to full charge because turning the starter motor is a vastly greater load than anything else in the car.

I've run into this lately. Truck could sit for weeks and start up no problem. Now, using it every morning to drop the kids off at school is killing the batteries because of the startup drain vs charging time.