Normally, my understanding is that power to the radio is cut when the ignition is turned off.

I am looking at installing a normal computer in a car (not an Android) and the problem is that if you suddenly cut power to a normal computer, it can cause data loss and other problems.

Therefore, I think what I want to do is set it up so that the car is always supplying power to the computer, so long as the computer is turned on. (Obviously, this would cause the battery to get drained if the computer is accidentally left on.)

Is there an easy way to do this on a Volvo 850, or not really?

1 Answer 1


The easy answer is to find/tap an always on source in the fuse box. Most radios have this, but they are usually low amperage feeds (they are used to maintain the settings in the radio). A good source of always on power may be the cigarette lighter or phone charger outlet (if so equipped). You'd need to test them for constant power as some vehicles switch these off either immediately at key off, or over a period of time to prevent power loss (controlled through the BCM). Most vehicles do have an always on source. If all else fails, run a new lead from the battery, but ensure you put an inline fuse into the circuit to protect other elements of the vehicle's wiring/electronics.

  • 1
    Be aware also that most 12v power sources in a motor vehicle will be on, except for when the key is turned to operate the starter. As long as the computer installed is not automatically turned on when the key is on, it should not be a problem, but don't turn the key to power, turn on the computer and then start the vehicle!
    – fred_dot_u
    Aug 30, 2018 at 14:44
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    If you choose a power source directly from the battery then starting the car will not interrupt it. There are power taps in most fuse panels that are always on and are not interrupted by the starting.
    – Moab
    Aug 30, 2018 at 15:02

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