This year’s “birthday present to myself” was a grip heater kit and a set of gel grips. The heaters can run straight off the battery or off a tap into a powered line like the headlight, but the best (and cleanest) way is to use a relay. A relay doesn’t just prevent you from draining your battery if the grips are accidentally left on; you can run the output into a distribution block to power other electrical devices that you might add in the future.

You can purchase similar setups from various retailers — the Dispatch 1 is a favorite of mine — but this project is for those of you who want to learn more about your bike’s electrical system while saving a few bucks in the process.

Parts List

  • 12V 30A automotive relay (Napa AR272)
  • 20A fuse (probably too much for just the grips, which I’ll discuss below)
  • in-line fuse holder
  • various electrical connectors (female, ring tongue, and quick connects)
  • 8 gang (connector) European style barrier strip
  • >18 gauge wire (red, black, and blue)

On Relays

The relay is the heart of this project, so I needed to learn what a relay does and how it works. Thanks to some industrious BMW guys, you too can learn the power of the relay: Relays: FAQ and Tech.

In this project, the relay is used to isolate my accessories from the rest of the bike’s electrical system. When the ignition is off, power to the accessory circuits is also off. When the ignition is on, power to the accessories is restored. This is accomplished by tying the relay to a non-essential powered wire such as the license plate light. In addition, if something goes wrong with an accessory, a fuse will cut power to the accessory circuits.

You can buy a suitable relay at places like RadioShack or an auto parts store. I purchased my relay at Napa for $14. It’s a 5 pin type and quite sturdy compared to the ones I saw at RadioShack. While most generic “automotive” relays are similar, refer to the schematic printed on the casing or packaging for the correct pin layout.

On Barrier Strips

The barrier strip, also known as a barrier block, terminal block, or junction block, is a centralized point where all the accessory connections are made. The strip is powered from the battery (via the relay) and also grounded from the battery.

I encountered two different kinds of barrier strips: a “European” style and the more common screw terminal style. Both kinds can be found at RadioShack. I chose the Euro style strip because it was rated for higher loads and connections are easier: simply strip the end of the wire and insert into the connector. The screw terminal type requires wires with fork terminal connectors or messy twists of bare wire around the screws.

More on this subject can be found at Wikipedia: screw terminal.

Now, on to the good stuff!

Open ‘er Up

First, I removed both seats. Then, I took a good look at the nooks and crannies around the battery. This is a good location for the relay and distribution block due to its close proximity to the battery and central location on the bike. It’s also fairly easy to get to and one of the more protected areas of the bike in terms of weather resistance.

The Diagram

Here’s how I wired things together:

Click the image to view it in full size.

Click the image to view it in full size.

Wiring the Distribution Block

The barrier strip I used has 8 pairs (gangs) of terminals. The goal is to create a positive and negative set of terminals (4 pairs each) on the strip. This is accomplished by connecting short jumper wires to four terminals on the strip, unifying them. Here’s a picture that better illustrates the idea:

The four pairs of terminals on the left side will be negative and the four pairs of terminals on the right will be positive. Note the longer wire soldered to the shorter wire. The longer wire will run to the negative terminal on the battery. The shorter wires are the jumpers. Never mind my shoddy soldering — I’m still learning! Here’s the negative side connected up:

There’s one additional wire that runs to the negative side, and that’s the wire connecting the distribution block to the ground pin on the relay. Once that’s finished, the process essentially repeats for the positive side. This is how the distribution block looked when I finished:

The wires that run from the distribution block to the relay and battery don’t have to be very long: 4 or 5 inches at most. I crimped female terminals to the ends of the relay wires to fit the pins on the relay. The end of the battery wire received a ring terminal to connect to the screw on the negative terminal on the battery.

The Low Power Source

Next up was figuring out a source for the power needed to trigger the relay when the ignition is turned on. The license plate light is a good candidate because it’s always on when the ignition’s on. The SV650 wiring diagram, shows a brown wire as the license plate light wire. The best place I could find for the tap was near the connector under the passenger seat.

Then, I ran the wire to the area near the battery and put a female terminal on the end.

Connecting to the Relay

Most relays, but not all, are labeled as follows:

  • 85: ground
  • 86: low current input
  • 87: power output
  • 30: +12V input

Following the diagram, I connected the negative wire from the distribution block to pin 85. The blue wire from the tap into the license plate light connected to pin 86. The positive wire on the distribution block went to pin 87.

The last connection is from the positive terminal of the battery to pin 30. It’s a good idea to have a fuse somewhere in between for additional peace of mind. The guide I followed for this project suggested a 20A fuse, but after some additional research, I’m pretty sure this is too high for the load that’s currently going to be on the accessory circuits (just heated grips for now).

Here’s what I ended up with:

At this point, things are still in the “work in progress” phase so nothing’s ziptied down yet. I’m also proud to say that everything worked on the first try! It was a good feeling to turn the ignition on and hear the relay click for the first time, and when I hooked up the heated grips and they turned toasty hot… well, I’m getting ahead of myself!

I’d be remiss if I didn’t mention the guide I followed for this project: Canyon Chaser’s Distribution Block/Powered Relay. It took me a few hours to complete, though I was working very slowly to make sure I had everything in the correct place. Not a bad way to spend a Sunday afternoon!


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{ 5 comments… read them below or add one }

1 E September 2, 2009 at 7:41 pm

Although you can and obviously did wire the relay in a way that it worked, the labels you gave the terminals on the relay are not exactly correct.

For instance, 85 and 86 are the ground and switch terminals. You can actually connect either terminal to ground and switch.

The same holds true for terminals 87 and 30. Technically, it does not matter which is which, HOWEVER, you will notice that many a relay has a 5th output in the center, this is usually labeled 87A. The purpose of this terminal is to provide power OUT when the switched terminal (86) is NOT receiving power.

A good use for this is to connect the positive end of an SAE connector to so that it can only output power while the bike is OFF. One company that makes use of the 87a connector for just such a purpose is Electrical Connection (http://www.electricalconnection.com/power-distribution/pplate.htm)

Because of this, it would be wise to update the labels for the terminals in your article as follows.

85=Ground
86=Switch
87=Power OUT
30=Power INPUT

Eddie

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2 Stacy September 2, 2009 at 8:35 pm

Ahh, I remember running into this when I was originally wiring everything together. If I recall, I followed the pin labeling on Canyon Chaser’s guide and did notice that it didn’t match up with some of the labeling on the BMW airhead guide. Your explanation makes a lot of sense, and I’ll try to update this article to be more accurate.

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3 Joe September 30, 2011 at 9:45 pm

How would you wire electronics into the barrier strip? I.E. where would you hook up the positive and negative ends to, say, a 12 volt socket and a gps unit wire on the barrier strip? Perhaps a picture with annotations/drawings on it would be appreciated.

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4 Joe September 30, 2011 at 10:51 pm

You know what, I just realized from the diagram you posted. Wonderful tutorial you have here…

Reply

5 Stacy October 1, 2011 at 11:37 am

As a clarification for others who may have the same question, you would attach the positive wire(s) to the side of the barrier strip opposite the red wires in this photo (the empty side nearest the top edge of the photo). The negative wire(s) attach to the side of the barrier strip opposite the black wires.

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