Fuse Tap For Adding Electric Circuit Power

[MrAl]

This is interesting.

Apparently if you want to add a power line to your car for powering some electronic device you add to the car you can use this adapter. It replaces the fuse with a fuse and attached power line. The power line goes to the new device being added.

To use i guess you unplug the old fuse and plug this thing into that open fuse space, then plug the fuse into this thing, then use the power line to power your new added device.

Seems like it would work pretty darn good with a few caveats...
1. Will the fuse cover still close properly. It looks like it might raise the fuse up by two fuse heights which may be a problem for closing the cover. Depends on clearance.
2. The heavy duty wire coming off the side will unbalance the forces on the fuse body which means it may cause the fuse to become unplugged as the wire tugs on the fuse either straight up or on some angle. This can be alleviated by a judicious placement of some tie wraps.
3. It has to be plugged in with the wire on the correct side i would imagine, so that the fuse can also break the connection to the wire coming off the side. If it was plugged in in reverse, the line would not be protected because it would connect directly to the main power with no fuse between.
4. In my 1998 v70 Volvo the fuse box is under the hood so the new power wire would not be in the passenger compartment it would still be on the opposite side of the firewall so i'd still have to find a hole in the firewall to get power into the cab area.

Probably the game ender would be #1 above the other three could be dealt with, because if the cover doesnt close that could cause a big problem. It would have to be tried. Maybe i can get some dimensions, i'll see what i can find.

[850 LPT]

I am using this exact thingy to power my aux. driving lights in the 850 and also in the S70. Works perfect, and the cover still closes fine. There is even an opening under the fuse box where the cable can be routed thru to the underside of the dash.
I can take photos tonight of what the install looks like, and I can tell you which fuse I used. It has to be a circuit that switches off with the ignition.

Dirk

[850 LPT]

This is what it looks like, fuse #4 works well for this.

[abscate]

A SKU and Amazon link would make this thread complete

[MrAl]

This is what it looks like, fuse #4 works well for this.

DSC_0058.jpg

Thanks for the info, now i know it will work if i buy one.

[MrAl]

A SKU and Amazon link would make this thread complete

Yes good idea. Here is just ONE such item but there are many others on Amazon...
WARNING: [check size before buying]

https://www.amazon.com/10-Pack-Add-circ ... KBP7R922VP

Here is a multi size one i think:
https://www.amazon.com/Electop-circuit- ... SDB3&psc=1

You can go through MVS to purchase but i am not sure how to do that yet.

I hope that works but if not just go to Amazon and type in "Fuse tap" and they come right up.

I would recommend checking to see that they are the standard size fuse for the car though because they alao have the smaller ones that wont fit in the Volvo fuse holders, at least not for mine 1998 v70.
That one i linked to could be a smaller one so watch out.

[abscate]

I think P80s use theATO style while the P2 cars use the mini style

Watch out for the taps that project sideways as they won’t fit in many fuse spots, of course

[abscate]

Hmmm, cancel the above warning. It looks like they designed it to ride above the fuses in the box per the picture in Dirks post

10 Amps would be about the current limit on a 16AWG wire on a total run of 2 meters, for a 3% voltage loss

[MrAl]

Hmmm, cancel the above warning. It looks like they designed it to ride above the fuses in the box per the picture in Dirks post

10 Amps would be about the current limit on a 16AWG wire on a total run of 2 meters, for a 3% voltage loss

I am getting 9 feet for a 3 percent drop.
#16AWG has resistance 4.016 Ohms per 1000 feet.
For 1 foot that means a resistance of very close to 0.004 Ohms.
At 10 amps, that drops 0.04 volts.
0.04 volts is close to 0.003333333 percent of 12 volts.
For 9 feet that means very close to 3 percent of 12 volts.
If instead we take the voltage drop 0.04 and 9 feet of wire that means 9 feet drops 0.36 volts.
0.36 volts is 3 percent of 12 volts.
So 9 feet causes a 3 percent drop to the nominal 12v car voltage.
More important probably is the drop itself, which is 0.36 votls, which may or may not be good. Then again a higher voltae drop may not affect some things either.
We also have the temperature rise to consider. If the wire is in a confined space the temperature rise would cause more of a voltage drop and it could be somewhat significant. We can calculate that based on the temperature rise although the temperature rise is hard to estimate not knowing where exactly it is installed.
The ratio of the resistance at 20 degrees C to the resistance at a higher temperature Tc=Ta+Tr is:
r=0.00393*(Ta+Tr-20)+1
where Ta is ambient temperature and Tr is temperature rise, both in degrees C,
and for many electronic applications a 60 degree C rise from 20 degrees C is acceptable.
The ratio of resistance at 20 degrees C to that at 80 degrees C is 1.1572 so that 3 percent goes up to close to 3.5 percent which is a drop of about 0.42 volts.

For #16 AWG wire i usually draw the line at 10 amps too,
To get a higher current wire in there, cut the wire off close to the fuse and splice in a heavier gauge wire. It's a good idea to use heat shrink tubing to insulate the connection or else use an insulated butt crimp connector good for both #16 and the heavier wire gauge (like #14). I would use the more flexible wire if using #14 or above because it is not as stiff. #14 and above are available with 7 strands and above, for example 37 strands. Obviously 37 strand wire is more flexible than 7 strand wire. I dont think we have to go to 37 strands though something with more than 7 strands though is a good idea.

[850 LPT]

I actually bought these from Autozone (in store), and yes 10 Amp max is also what the manufacturer says. I can double check, but if remember right, mine are made by Buss.