Car fuse 'bridging' to combat parasitic draw?

[cannondale0815]

The title may not make a whole lot of sense to someone who understands more about car electrics than me, but I hope it makes a bit more sense once you read the following.

It appears that my aftermarket Android radio in my 2014 VW Beetle is causing a parasitic draw on my car's battery, even when the car is parked and ignition is off. This caused my old battery (which has now been replaced, as it wasn't in good health anymore anyway) to completely drain when the car was parked for two weeks.

I identified the fuse in the engine compartment fuse box that is responsible for the radio (when I pull it, the radio does not turn on anymore). The circuit this fuse is on appears to be always on, not ignition switched. Is there a way for me to somehow bridge this fuse with a different one in the same fuse box that is ignition switched, and therefore make the radio fuse be ignition switched as well?

I believe a relay may do the trick (have an ignition switched fuse be the trigger to engage the relay), but is there maybe a simpler way of connecting one fuse slot to another by means of some inline fuse wiring?

Thanks
-J

 

[rapparee]

This sounds like it would be easier if you could sort out the lives at the rear of the radio.

The permanent live should just be for storing radio station frequency etc.

The switch lives for turning the radio on when the car is running.

 

[ruston]

There will be more than the radio drawing current when the vehicle is standing for a long time . The vehicles ECU goes into sleep mode but still draws a small amount of power during shut down. This can be significant over a long period and can leave the battery below the power required for starting .
As @rapparee has said , sort the radio out so that the switched live is only activated in the accessory position of the ignition switch.

A way of combating battery discharge on vehicles that stand a long time is to fit an automatic trickle charger. Don't use an ordinary charger as you may overcharge and ruin your battery.

 

[cannondale0815]

Thank you @rapparee and @ruston for your responses. The radio simply plugs into the proprietary factory harness of my VW. Short of snipping & rewiring some stuff, there isn't much control I have over how it's connected to the power line. From reading elsewhere, some people blame parasitic drain on the canbus module of those aftermarket Android radios, which apparently stays always on (the radio is not supposed to turn off immediately but instead is supposed to gracefully shut down when the ignition is off and the driver door is opened -- and that is facilitated by the canbus module that's always powered).

However, I thought I could cheat by finding a way to have the radio fuse switched off forcefully when some other ignition-switched fuse is turned off. In some other forum, someone says the following, but it doesn't fully make sense to me:

"Make a bypass wire with a fuse inline. It’s just a bit of wire with a 15A fuse inline and spade connectors. One side of the wire in the radio slot of the fuse box and the other from an empty slot that only has power when the ignition is on."

P.S.: This is from a several year-old forum post
P.P.S: My car is mostly parked in a public garage without access to a power outlet where I could plug a battery tender into -- so no ability to trickle charge

 

[telectrix]

if leaving car unused for 2 or 3 weeks, ''''
1.leave the handbrake off, or it may seize on.
2. start it up and run engine for 20 minutes once a week (not in a closed garage).

 

[PEG]

Hi,just drop a battery lead off,or,fit an isolator....it will not cause anymore inconvenience,than disconnecting the memory/permanent feeds,to the radio.

I would also check the current draw,when the radio is unplugged.

 

[cannondale0815]

So I have gathered some more evidence related to my parasitic drain.

Through voltage-drop measurements across all fuses, I found that one particular 20 amp fuse (no. 23 in the interior fuse panel) is having a voltage drop of .6 mV between the two contact points, which, according to this voltage drop chart, translates into 187 milliAmps.

The test was performed with all door latches in the locked position, then waiting a couple of hours to ensure all systems enter sleep mode.

According to a fuse diagram I found somewhere for my car model, the fuse in question (fuse no. 23 in interior panel) serves the following purposes:

Rain/light recognition sensor -G397-
Vehicle Electrical System Control Module -J519-
Telephone Transceiver -R36-
16-pin connector -T16-, data link connector -GX22-

Also, the aftermarket radio is not the direct source of the parasitic drain -- the drain continues even when the respective fuse is completely pulled, and there is also no measurable voltage drop at that fuse.

Any suggestions appreciated!