Arduino project for my car

Projects General Guidance
1

Hi,

I'd like to begin an Arduino project to interface with my car's CAN-BUS and be able to remotely control things such as windows, ignition, etc. My plan is to use an Arduino ADK board, a CAN-BUS shield and a cheap android cellphone/device connected through the arduino's ADK USB port. The Android device would give me 3G connectivity, GPS, Bluetooth, Wifi, etc. all at the same time, along with enough CPU/memory to do more complex things such as wireless tethering.
To lower the battery drain, some things such as GPS and Wifi would only be turned on when the car is on (there would be no screen connected except maybe when doing maintenance) and, when the car is off, the Android device would run on battery as much as possible only charging when the device's own battery falls below a certain threshold (some android devices can turn off usb charging via software).

My only question is if the car battery can take such a device running 24/7.
I use my car to drive to/from work everyday (about a 20 min drive) but it could eventually happen to stay in the garage for 2 or 3 days in a row (if I plan to stay away for longer than that I would disable the device altogether).
I suspect that the Arduino board itself along with the CAN-BUS shield will consume very little energy, but I really can't say about the android device.

I really have not seen many projects like this around. Most such projects use a full-blown linux computer with attached devices and a huge battery of it's own. Most arduino car projects I've seen are more along the lines of getting engine data from the ODB-2 interface.

I know there are other challenges for car projects such as trepidation and extreme temperatures, but these can be solved after I begin. The only real deal-breaker is if the car battery can't handle the extra load.

Any ideas?

2

My only question is if the car battery can take such a device running 24/7.

Probably. There's always stuff running in a car. Usually there's a clock, maybe a security system, maybe remote door lockss that have to be running and "listening" for an unlock code.

I built a microcontroller based car alarm fro my van many years ago. Sometimes, the van sits for a few months. I don't know how much current it's taking, but it runs 24/7 and an LED blinks when it's armed. After a couple of months, it's OK. Sometimes after several months, it won't start without re-charging the battery. But, I assume that would be the case with alarm or not...

3

Try multimetering it lol, i did my 93 mitsubishi and got 53ma when entirely off, i just put the meter on the terminal and the wire so when i took off the wire the path existed thru the meter and saved me resetting my clock, radio etc
Im not sure the actual mah rating of one of those batteries but a common example is th parking lights left on, my car was 4.5 amps, and it barrly starts the next morning so say 10 hours maybe so you probably have around 300 amphoures in a general battery, tho its not good to draw it low regularly because its not deep cycle
a simple solution is monitor the voltage and if it drops below 12.2-5 stop draeing power
Most batteries are nominal 12.8 at rest, 11.5 at completely dead
I made a car system that only did lights and starting, with bluetooth and a tft screen, w/sd card and it draws 350ma just being on, the mege2560 took 80 ish ma by itself, so that wasn't causing me problems day to day, although I disconnected it if I didn't drive my car a few days, maybe you could just put it in a sleep mode waiting for that phone connection to wake