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I am working on a project where my Pi is always connected to a vehicle to provide its GPS information.

Seeing such a device must be always turned on, I am attempting to tap into a battery line that always has power.

My question is, will this deplete the vehicle's battery overnight? Or in two days if the vehicle hasn't been driven?

Other GPS Units, car alarms are always on 24/7 and that doesn't affect the battery. I left my phone charging overnight in the car and it had no effect on my battery.

Secondly, to use less power, is it wise to remove the LAN chip? Or is that a myth?

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  • a better choice would be to tap into an ignition source. If the car is parked there is little need for GPS data and this will not drain your battery. Note this will likely require a voltage regulator to turn the car's 12 volts into the % Volts needed by the Pi. – Steve Robillard May 13 '16 at 3:03
  • @SteveRobillard I have the voltage handled, I intend to soder a usb charger. However, wouldnt all this sudden switch off and sudden switch on damage my sd card soon? – Grace May 13 '16 at 3:46
  • there are ways to handle that using a battery. You might want to look at the Magpi,youtube and instructables for ways of doing a graceful shutdown. – Steve Robillard May 13 '16 at 3:48
  • I'd avoid instructables. Most of the stuff there is just wrong. – JayEye May 13 '16 at 4:03
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The Pi draws about 300mA at 5V, plus whatever your GPS unit would draw. Ignoring the small losses associated with a (switching) step-down converter. Say a total of 2W. That would be equivalent to drawing 1/6A at 12V. If you have a 60Ah battery, it would last for 360h, or 15 days, give or take. So long as you move your car more than once a week, you should be fine leaving it on at all times.

If you want to be extra fancy, build a little circuit with a relay that requires a pulse every ten minutes, otherwise it turns off the relay. Use a cron script to reset the circuit every minute. Have the Pi detect that it hasn't moved in, say, two hours, and do an orderly shutdown. Since you'll no longer be sending a reset pulse to the relay circuit, it will time out and turn off the Pi (and possibly your GPS receiver).

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  • Would you suggest removing the LA chip? There is no need for it and I read removing it lowers the consumption * 3. Also would running the lite version of the Jessie OS be of much help? Since I'm sure the desktop version has more services running? – Grace May 13 '16 at 11:02
  • While I'm at it, what about stripping out the components I don't need, audio, 3 USB( only need one),camera outputs, LAN chip? – Grace May 13 '16 at 12:09
  • do you actually have the kind of skills necessary to desolder BGA components? – JayEye May 13 '16 at 16:44
  • I'm willing to break a few eggs to make this omelette. :) but I actually have associates who do – Grace May 13 '16 at 16:58
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I just wanted to let you know that I actually did this and had some bad results. The upvoted answer is correct that your battery will last a long time while powering the Pi. What he doesn't mention however, is that if you don't drive for 2-3 days, your car will still start but the voltage drops so low that your Pi reboots.

Also since I did this I started having the electrical system in my car go a bit haywire, the security system only works half the time and my horn honks itself while driving. On top of all that my Pi died eventually, probably from the bad power. Now I want to disconnect my next Pi from the car's battery and add a separate car battery just for the Pi.

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  • Even from the beginning, and by just imagining it, I have always thought, that a separate battery for the raspi and to never tap into the car's power supply. – typelogic Dec 9 '18 at 10:54

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