BMW K bikes (Bricks)

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1Back to top Go down   Adding accessories Empty Adding accessories on Sun Aug 24, 2014 5:38 pm

Rabidchiwawa007

Rabidchiwawa007
Platinum member
Platinum member
Hey guys,

So, I'm in the middle of converting my '92 k100RS in to an "LT" (quotations because obviously not all the bells and whistles will be there), and I'm curious as to where I can plug accessories in to the system.

The accessories are:
-power windshield (got that circuit working!)
-radio (I told myself I'd never have a huge fairing or a stereo on a bike, but then I started commuting 80+ miles daily on one)
-possibly heated grips in the future some time

I have a couple options as far as I can tell:
-The fuse box has one of those white circular connectors that's meant for an alarm system I think.  Would that work?
-I could run positive energy from something that's already on the circuit, like the tail light.

The power wire that came with the radio is pretty small gauge, so I think I can connect that to almost anything on the bike.
The windshield, however, I don't think a very small gauge wire is a great idea for that.

My reasons for avoiding straight to the battery are, first, to avoid accidentally leaving things on when the ignition is off, and second, to not accidentally run the starter motor with things like the radio and windshield going as it could probably harm those circuits.  I may as well make use of the load shed relay.


Thanks in advance.



Adding accessories OmGTxAJ


__________________________________________________
1968 BSA Lightning
1991 BMW K100RS 16v with K1100LT fairing
    

2Back to top Go down   Adding accessories Empty Re: Adding accessories on Sun Aug 24, 2014 6:56 pm

robmack

robmack
Life time member
Life time member
I suggest that the best solution is to buy/build an auxiliary fuse block to supply your LT accessories.  It gives you the greatest flexibility for distributing power to aftermarket accessories.  The big advantage to auxiliary fuse blocks is that you can get the primary supply directly from the battery yet have the advantage of switched circuits by use of a suitably sized relay controlled by a low-current wire somewhere on the harness.  Tieing your accessories into existing circuits potentially overload those circuits since the manufacturer sized the wires and fusing accordingly.

Popular aftermarket fuse blocks are Centech and Fuzeblock .  Both these are expensive IMO but are perfect for people who don't have electronics backgrounds.

Duck published a page on auxiliary fuse blocks for the K-bikes .

There is a local Toronto guy who designed and published a circuit card to offer a switched three circuit fuse panel .  This card is 5 x 5 cm and easily fits inside the K100 electrical box.  You can tap power from the start relay and Grey/White wire.  Contact me if you want a blank PCB as I have spares.

Rated current demand from the electric windshield motor is 5.8 Amps maximum.  This can be handled by 14 GA (1.5 mm2) primary wire and the power connection on the alarm circuit can supply that need.  It would be protected through Fuse #7.
Wire selection article by Don Eilenberger

Reference:  Amps and Wire Gauge
AWG to Square Millimetre conversion


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

3Back to top Go down   Adding accessories Empty Re: Adding accessories on Sun Aug 24, 2014 11:26 pm

Rabidchiwawa007

Rabidchiwawa007
Platinum member
Platinum member
Wow, awesome info, thanks.

So, it basically sounds like this to me: use the starter relay's grey/white wire to run to an auxiliary fuse box which then essentially powers all my addon accessories.  Is this correct?

If that is the case, I could really for-go an auxiliary fuse block and just put in-line fuses in the positive wire for each accessory, pulling power from that same grey/white wire.  It'd be a bit messier, but I have all the materials to do it that way.

Regarding a switched circuit, this essentially would act like the load shed relay, as it is essentially being controlled/powered by a wire on the harness that is controlled by the load shed relay?

Apologies for all my questions, I'm quickly becoming better at building circuits and it's exciting!

Side note: the LT handlebars I bought awhile back apparently came with working heated grips on them!  Woohoo!


__________________________________________________
1968 BSA Lightning
1991 BMW K100RS 16v with K1100LT fairing
    

4Back to top Go down   Adding accessories Empty Re: Adding accessories on Mon Aug 25, 2014 2:56 am

robmack

robmack
Life time member
Life time member
@Rabidchiwawa007 wrote:Wow, awesome info, thanks.

So, it basically sounds like this to me: use the starter relay's grey/white wire to run to an auxiliary fuse box which then essentially powers all my addon accessories.  Is this correct?
Not quite.  Use the battery feed that attaches to the starter relay as a convenient tie-in point for your switched auxiliary fuse block.  Tap into the Grey/White wire on fuse #2 as a source of switched signal to turn on/off your auxiliary  fuse block.

@Rabidchiwawa007 wrote:If that is the case, I could really for-go an auxiliary fuse block and just put in-line fuses in the positive wire for each accessory, pulling power from that same grey/white wire.  It'd be a bit messier, but I have all the materials to do it that way.
No, that's not going to work.

@Rabidchiwawa007 wrote:Regarding a switched circuit, this essentially would act like the load shed relay, as it is essentially being controlled/powered by a wire on the harness that is controlled by the load shed relay?
Yes.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

5Back to top Go down   Adding accessories Empty Re: Adding accessories on Mon Aug 25, 2014 4:39 am

Rabidchiwawa007

Rabidchiwawa007
Platinum member
Platinum member
Ahhh, I see now.  Okay, so the new relay turning things on and off together with the load shed relay is dependent on how I wire everything to it.  Starting to make sense.  Just need to figure out which relay pins go to what now.  Once that is done, the end result should be power flowing in to the relay, going through a switch inside it that is (de)activated by the starter button at start, and then back out to the auxiliary fuse block, correct?



Side question: I've read about the different wattage alternators that come with these bikes depending on the model.  For example, I believe the old police versions of the K's came with 750watt alternators. I believe stock alternators are 450watt on regular K's.  Is that going to be able to keep up with normal operation plus heated grips, a stereo, and occasional windshield motor use?


__________________________________________________
1968 BSA Lightning
1991 BMW K100RS 16v with K1100LT fairing
    

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