A friend asked advice for adding a relay to carry power for accessories. I presently use the ignition switch for lighter loads by way of the city light wires but planned to add a power relay for these loads. Here is the response to his query.
If this doesn't make sense, let's talk.
I hope that this is useful to someone.
>regarding the relay, where would you >recommend to fix it?
I'm trying to remember what the relay is intended for? Sorry but my brain is not working well (VBG) and I get so many posts....
My headlight relays are under the tank inside the frame tubes, just behind the radiator tank. I need to add another relay for accessories such as grip heaters so that they can't be left on accidentally. I may mount that one in the same area or maybe in the fairing under the dash. Where it goes doesn't matter much so long as it is solid as I do some mean off-road.
>and from where you are taking the juice?
I recommend taking power (juice) from the starter relay (starter solenoid) which is under the same rectangular black plastic cover on the bike's left side above the side stand but in front of the frame tube. IMO it is better to take power from the relay rather than the battery because the connection at the relay is less likely to be exposed to corrosion and does not have to be disturbs when servicing the battery.
>would it be possible to make it work only when >the engine isrunning and not when you switch >on (u know before starting the engine)? to add >even more safety and to avoid to pump the >battery until the engine is on and running.
Yes, I hadn't thought of doing that but it would be a very nice touch. I have done this before but simply hadn't considered doing so for the KLR. Your thinking is ahead of mine! Thanks!
It would be simple to have the relay circuit turn off while cranking (using the starter) but much more complex to have the relay off with the engine not running. In order to have the relay not operating when the engine is not running there needs be some logic applied such that the circuit is energized by a condition which differs from "key on" and "key on engine running".
In order to have the relay off when the starter is operating (I'm going to do this ASAP) simply ground the relay to the heavy starter cable on the starter side of the starter relay.
The way this works is that the relay draws a very small current (has a small amperage flow) to close/keep closed the relay contacts. If the relay's energizing winding (the magnetic coil which operates the relay's switch contacts) will be grounded (connected to the bike's common negative which is considered to be the frame) through the starter motor. To repeat that without the brackets: The relay will be connected to the battery negative by the starter motor. This may seem to be a strange way of connecting the relay but consider the relay's current flow is less than one ampere while the starter motor's current flow (during cranking) is about 75 amperes. From this it can be deduced that the starter motor will happily connect the relay to ground without either being affected. In other words, the relay will operate normally but the starter motor will not operate at all.
OK, now consider what will happen when the starter relay closes (switches on): The relay connection whichwas connected to ground through the starter motor was also not connected to the battery positive because the starter relay was open. When the starter relay is operating (closed) the relay will no longer be grounded because battery positive voltage will exist at that point because there is current flow through the starter and the voltage drop is in the starter motor. In this state the relay will have battery positive applied to both sides of the relay's winding so there will be no voltage difference across the winding and no current will flow.
Ground the accessory relay to the starter and the relay will operate until the starter operates. When the starter operates the relay will cease until the starter is off.
Hope that's clear.
The problem of having the relay operate only when the engine is running is more difficult but could be accomplished by controlling the relay by a circuit which detects pulsations in the ignition primary. This is beyond what I can do without research as haven't done this kind of design for years.
A simpler solution for operating the relay, engine running only would be to install a low pressure switch into the oil pressure test port. Note that this needs to be a switch which is turned on when pressure is applied. A low oil pressure warning light (idiot light) switch will not work because it operates in reverse of what is needed. Yes, an idiot light switch can be made to work is a normally closed relay is used but I'm not up to going through the explanation unless someone really wants to know.
It would be simpler to wire so that the relay comes on with the ignition switch and kicks off while cranking. This makes great sense as it avoids the load of accessories stealing power which might help the starter.
I'll wire the KLR so that the headlight goes off also during cranking as headlight, bar heaters and electric vest might make the difference between a start and no start. Since it is only a matter of selecting an alternate ground connection it is a no-brainer, IMO.
Here's what I propose for you to connect your relay:
1) Decide where it is best tolocate therelay.
2) Connect a fused 14 gauge wire to the positive (battery side) of the starter relay to one relay contact connector.
3) Connect an 18 gaugewire from one relay winding connector to the starter motor side of the starter relay.
4) Connect an 18 gauge wire from the "hot" city lightwire to the other relay winding connector.
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At this point the relay will "click" when the ignition switch is turned on.Youmay wish totry it to confirm. A test light connected to the remaining relay contact connector should light when the ignition switch is on. The test light should go off while cranking the engine.
5) Connect the other relay contact connector to the accessory which you wish to operate.
I'm going to post this to the DSN_KLR650, Dual SportBC(KLR)and KLR650.net groups in case someone finds the concept to be useful. Another reason is that I may have missed something which is peculiar to the KLR650 so someone will likely point that out. Wait a day or so before you start.
I'm going out to the garage to rewire my KLR. Mine has the following circuits:
1) Cigarette lighter socket for GPS and tire pump.
2) Electric vest (wired directly to power) plug also used for Motion Pro charger. This circuit will remain as is so the charger will function.
3) Headlight high beam relay and low beam relay.
4) Dash lights.
5) Electric bar heaters. Presently wired directly because I haven't gotten around to pulling the tank to run wires.
6) Accessory power plug on left bar for sound system linear amplifier.
7) High mount LED brake light in Givi. This will stay as is.
8) Headlight high beam OFF switch. This will remain as is.
9)4 way flasher switch. This will remain as is.
10) Radiator fan on (full time operation) switch. This will remain as is.
Hope this is useful/comprehensible. I haven't proof read this so hope it makes sense.
Norm