Wiring relays for accessory socket and headlight

[79beem]

Just about to do this little mod and was wondering if there is anything I should be wary of.

I found this site for a R1200GS accessory relay set up which seems fairly straight forward.

http://www.r1200gs.info/howto/relay.html

The guy on this site states the need to find a good source of "switched power" usually a green wire with blue stripes according to him. Is this the same for our bikes, or is there a different/better source?

He also includes info on putting an optional on/off switch in the circuit, is this really needed?

I only intend on charging my phone on the road for when/if ever I go camping.

But, if I ever wanted to add a pair of small driving lights would the alternator handle both at the same time? Is there a max wattage on the driving lights?

Which leads me to my next question.

Has anyone had any experience with Eastern Beaver H4 Kits?    http://www.easternbeaver.com/Main/Wiring_Kits/H4_Kits/h4_kits.html

If, as they claim by installing there kit you get brighter bulb output without overloading the system, doe's this mean I can run more accessories as long as there related circuits are relayed?

If so the "H4 Single with Driving Lights Lead" looks like a great setup?

Cheers in advance.
 

[Barry]

If I was only going to draw a few mA for phone charging I wouldn't go to the trouble of using a relay as the relay coil will itself draw a few mA continuously whether the charger is connected up or not.

The usual location for an auxiliary socket is somewhere around the rear sub frame. A Green/blue wire is still correct for your model and one convenient one which is a switched live is the spare spade connector on terminal 15 of the rear ignition coil. I stress I would not use this if you intend to draw a higher current as that would increase the voltage drop in the ignition circuit. 100mA would do no harm though. Alternatively you could pick up a live feed from the fuse box and control it with a switch.

Driving lights are a different thing altogether and a relay wired through the lighting circuit is the way to go. The claims about brighter lights are due to the relay largely eliminating voltage drop in the lighting circuit so the actual voltage at the bulb is higher. The other benefit is reducing the current being carried by the light switch which will prolong it's life.  Using relays doesn't mean you can continue to add more and more extra load without upgrading the alternator.

[bruce_launceston]

If you want power to use while camping just wire the socket the same as the OEM BMW socket. It is directly wired to the battery with a 10 amp fuse in the power line.
Then you can use your accessory socket for charging phones or a LED lamp or other low drain accessory without having to leave your key in the ignition and turned on.

I would only wire accessories that you would use with the bike running eg heated grips etc to a switched circuit.

BTW, it's not hard to wire up your own light loom to custom fit your bike, as Barry said just make sure you use a relay to protect your light switches.

[montmil]

Prior to spending a tidy sum of money for electrical accessories, suggest you tally up the power draw of those lights, etc and determine if your '79's alternator/charging system will handle the loads without draining the battery and leaving you "in the dark" so to speak.

Your Powerlet plug for the phone is not a concern as its draw is extremely low.

[nhmaf]

Eastern Beaver makes a pretty good kit.  I did a write up of their horn relay kit in this thread:
http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?num=1342832743

I would expect that their headlight kit would also be pretty good and easy to follow if you wanted to use it on your bike.  

As the other  have posted, you only have 280W (max) charging system output - this was alot back in the early 80s, but it is trivial in this day and age.  A number of folks have used some LED-based driving lights which are less power hungry and will probably suffice with the existing charging system, provided that you don't just putt-putt around town with them, or at least put the bike on a battery tender when you return home.     Otherwise, Omega and Enduralast both offer replacement rotor and rectifier charging system kits which will boost you up to 400/450W of charging output, and that will cover your lighting needs...

[79beem]

Thanks everyone for your input, much appreciated.

Would it be better to install a relay in the accessory circuit with an on/off switch on switched power for bigger draw accessories.
And a separate power socket direct to the battery for low draw items, as Bruce suggests ?

Bruce, I thought about making my own setup but the Beaver kit plugs straight into the existing h4 socket without any modifications,making install/removal very easy.  

How much power is needed to charge the battery and run the bikes other electrical requirements before the driving lights are added?

How do I calculate power draw as Monte suggests.

I'm now looking at a pair of 35w driving lights.

[bruce_launceston]

I still don't understand why you need a switch, a relay is only required to protect a switch designed for a lesser load (such as the ignition or the OEM light switch).

If it were me I would just wire the accessory socket with larger cable and fuse for high drain accessories.
If you do want to install a dedicated switch in this circuit just use a suitably rated switch without the relay.

LED driving lights would be my choice these days but I used to run a 55 watt H3 driving light without any problems on my R65LS.

[79beem]

Rapidly getting out of my depth here.

 I'm going off what the 1200GS guy suggested as an option as far as the switch is concerned. That's why I questioned its necessity in my first post.

My limited understanding of a relay is that it is itself a kind of switch and reduces stress on the circuit?  

Thanks for your patience.

[Barry]

Reading the 1200GS article again as you say he described the switch as optional and also described the reasons why he had incorporated a relay to feed the auxiliary socket. Having decided to power the auxiliary socket via a relay he needed to incorporate a switch that would energise the relay enabling the accessory socket to be used when the ignition was switched off. I suggest implementing the 1200GS article in full in this way may be too complex for most people's  needs.

In my view no relay is needed or desirable for an auxiliary socket as it adds unnecessary complexity.

If I was adding an auxiliary power socket I might also want to use it as a simple and neat way of charging the battery so that would also rule out connecting it to a switched live. I would just connect it to the existing fuse board or direct to the battery via a suitable in line fuse.


The head light relay is straight forward and no switch is needed.  As you say a relay is just an electrically actuated switch and the purpose of the relay is to bypass the light switch and various wiring connections. The main benefit is usually considered to be reduced voltage drop which equals brighter lights. An incidental benefit is the handlebar light switch now only sees the relay energising current which equals less stress and longer life.  This incidental benefit becomes essential when adding substantial extra electrical load to the lighting circuit which would overload the original light switch.

[79beem]

Ok, so it seems the general consensus for a low draw accessory socket is to connect via a fused wire to the positive battery terminal with no relay.

The addition of the relay protects the original system and allows for higher draw accessories if needed. The option of the on/off switch allows access to power for the same socket with or without the ignition on but allows the socket to be turned off if needed.

I still need some help figuring how much power is needed to charge the battery and run the bikes other electrical components before the driving lights/accessories are added?

I found this site http://www.powerlet.com/learningCenter/excessCapacity

Is this correct?

If so, at what rpm does the alternator produce 280watts?
  

[montmil]

Ok, so it seems the general consensus for a low draw accessory socket is to connect via a fused wire to the positive battery terminal with no relay.

The accessory socket for phone charging or a GPS, etc won't draw enough power to require a relay. With a relay, you simply add the complexity of a switch. I have a Powerlet socket on one of my bikes; occasionally use it to charge my phone while riding along.

The addition of the relay protects the original system and allows for higher draw accessories if needed. The option of the on/off switch allows access to power for the same socket with or without the ignition on but allows the socket to be turned off if needed.

Actually, a relay does not automatically permit successful use of higher draw accessories. Relays do protect small switches -like the those for driving lights- to draw their electrical power directly from the battery, thus not over-loading smaller gauge wires in the harness. Thinner wires act as resistors. That's the primary reason that people see an increase in their light's brightness after a relay upgrade.


I still need some help figuring how much power is needed to charge the battery and run the bikes other electrical components before the driving lights/accessories are added?

I found this site http://www.powerlet.com/learningCenter/excessCapacity

Is this correct?

Could be. But notice the bikes listed have greater alternator electrical production than our older Airheads.

If so, at what rpm does the alternator produce 280watts?

Low rpm putt-putting around town, on a stock Airhead, will drain the battery and teach you how to do a run n' bump to get home. Expect full charging to the battery to occur around 4K revs. And that means some steady riding at that rpm point. All part of the Airhead learning curve we've all gone through.

If you want the driving lights, some heated gear and an on-board cappuccino machine, you'll need to spend some serious money to upgrade the bike's charging system. A relay alone will not help. If it would, you wouldn't see these powerful alternator systems required on these new bikes. No way around it.

[Barry]

what rpm does the alternator produce 280watts?

Strictly speaking it's a 20 Amp alternator and at a nominal 14 Volts that would give 280watts but to start with some voltage regulators are set a a little lower at 13.8 volts and with voltage drops in the system it's unlikely the output would exceed 270 watts and only then when all the connections are perfect. A high set point or adjustable voltage regulator can help increase output slightly.

Popular wisdom would have you believe full output isn't achieved until 4000+ RPM.

Reading the link below suggests Snowbum measured it at only 2850 RPM which is a surprising figure.

http://bmwmotorcycletech.info/AftrMrktAlt.htm




I'd calculate your 79's minimum operating load as follows:-


Headlight  55W

Tail light 5W

Instruments 6 W

Ignition maximum 35W at idle falling to 20W when cruising

Total 101W

Add intermittent loads of 42W for turn signals and 21W for brake light. You would have to average the real effect of these intermittent loads according to how you use the bike but I would estimate it's typically an average of only 5W unless the bike is continuously in heavy traffic. BMW's already have several relays as standard which might add a couple of watts but that's just nit picking.

[79beem]

Thanks for the clarification Monte and Barry.

Barry, what do you mean by a high set point?

So if the bikes only giving 270 Watts at best and I'm not excessively braking or turning.

That leaves 165watts give or take.

Shouldn't that be enough for incidental phone charging and a pair of 55w driving lights with a bit to spare?

[Barry]

A high set point voltage regulator was fitted by BMW to authority bikes to help them deal with large accessory loads. These regulators were set at something like 14.3 - 14.5 volts which improved low speed charging a little. Using one doesn't mean you get 14.5 volts x 20 amps = 290 watts because the alternator may not be able to achieve that. The reason why is probably beyond useful discussion here.

Your voltage regulator if original is a mechanical type and they can with care be adjusted.  I have set mine higher but unless you have the test gear needed it probably easier to buy a high set point or adjustable electronic replacement. All the info is on Snowbum's site for any of these options.

Answering your last question is hard because there's more to it than the simple figures.

I don't know how often and for how long you ride but let's take a senario that's not untypical.

Before you set out for a ride the bike has been stood for several days so unless a float charger has been used the battery may already be partially discharged due to it's normal internal self discharge rate. Starting takes a little more out of it so for the first part of the journey the alternator has to provide some charging current to the battery as well as meeting all of your calculated electrical loads.

So probably not an issue for long high speed journey's but short commutes would not recharge the battery with those loads.

[georgesgiralt]

Hello !
In your calculations, you forgot the parking light which add a whooping 5 W....