BMWBMW Square Route Rally Motorcycle Electrics By Jerry Skene

BMWBMW Square Route Rally Overview of Seminar Volts, Amps, Watts & Ohms –What they measure and how they are used (includes Ohm’s law) Batteries & charging Adding lights and other accessories Common tools & supplies

BMWBMW Square Route Rally Volts Measure of the electric potential between two conductors, or the ability to move an electric charge through a resistance Motorcycles use a 12V DC (direct current) system Measured with a voltmeter ignition-off voltage is ~ 11.9 volts operating voltage is ~13.8 volts (lowest lethal voltage is ~ 60 volts)

BMWBMW Square Route Rally Amp (Ampere) Measure of current flow through a circuit Headlight bulb draws ~ 4.5A Tail light bulb draws ~ 0.4A, or 400 milliAmps (mA) Electrical symbol for current is I Minimum lethal current through the human body is 80 – 100 mA

BMWBMW Square Route Rally Watts Watt is a unit of electrical power (P) Corresponds to the power developed in a circuit by a current of one ampere flowing through a potential difference of one volt: Power = Volts x Current (I) a headlight connected to 12V Volts, drawing 5 Amps consumes 12 x 5 = 60 Watts

BMWBMW Square Route Rally Watts, cont’d BMW motorcycle alternators provide the following electrical power: /5 180W R90s 238W 1000cc to `80 250W recent R/K bikes400 – 600 W K bikes (pre-2005)700W K LT840W

BMWBMW Square Route Rally Ohms (Ω) A Ohm (Ω) is a unit of electrical resistance An ohm is the resistance that produces a potential difference of one volt when a current of one ampere is flowing through it. A typical 60W high beam bulb has a resistance of 0.4 Ω. 5’ of 18Ga wire has a resistance of 0.03 Ω.

BMWBMW Square Route Rally Ohm’s Law Very useful law relating voltage, current and resistance States that Voltage (V) across a circuit is equal to the current (I) times the resistance (R): V= IR or I=V/R or R=V/I So… the voltage drop across a 5’ length of 18Ga wire (R=0.03Ω) carrying 5A of current is…. V=0.03 x 5 = 0.15V

BMWBMW Square Route Rally Ohm’s Law Use Ohm’s law to calculate the size of fuse needed to power an 80 watt heated vest: P = 80W V = 12V (P=V x I), so I = P/V or 80/12 = 6.6 Amps (next larger common fuse size is 7.5A)

BMWBMW Square Route Rally Wire Gauges Measured in mm 2 or gauge # American Wire Gauge) Can use resistance table to determine total resistance of added wiring Cross-sectional area Overload Typical Use current rating 0.5 mm² (20 AWG)3 A instr., turn signals 0.75 mm² (18 AWG)6 A headlight 1 mm² (17 AWG)10 A h/l ground 6 mm² (10 AWG)30 Abattery

BMWBMW Square Route Rally Batteries & Charging Motorcycle batteries are of the Lead Acid design There are several variations of Lead Acid: –Wet Cell (flooded):serviceable, and maintenance free –Gel Cell –Absorbed Glass Mat (AGM) –Gel and AGM require less service than flooded Lead Acid –Gel Cell and some AGM batteries may require a lower charging rate –your motorcycle’s charging system usually dictates the type of battery you require –Gel cells have a lower recharge voltage, and can be damaged by too high a charge rate – best to use a Gel charger

BMWBMW Square Route Rally Batteries & Charging A fully charged battery should read V Sulfation occurs when the voltage drops below 12.4 V Most premature battery failures are caused by sulfation buildup – a result of losing charge Buy a trickle or smart charger, and use it frequently.

BMWBMW Square Route Rally Batteries & Charging Common causes of premature failure: –Battery sits too long between charges. As little as 24 hours in hot weather and several days in cooler weather. –Battery is stored without some type of energy input (self discharge). –"Deep cycling" an engine starting battery. Remember these batteries can't stand deep discharge. –Undercharging of a battery: charging a battery to 90% of capacity will allow the 10% of battery chemistry not reactivated to sulfate the battery –Heat of 100º F increases internal discharge. As temperatures increase so does internal discharge. A new fully charged battery left sitting 24 hours a day at 110º F for 30 days would most likely not start an engine. –Low electrolyte level - battery plates exposed to air will immediately sulfate. –Incorrect charging levels and settings. Most cheap battery chargers can do more harm than good. See the section on battery charging. –Cold weather is also hard on the battery. The chemistry does not make the same amount of energy as a warm battery. A deeply discharged battery can freeze solid in sub zero weather. –Parasitic drain is a load put on a battery with the key off. This can drain a battery in a few days

BMWBMW Square Route Rally Adding Lights & Other Accessories The most common addition is driving or fog lights Wire these directly to the battery through a fuse and relay

BMWBMW Square Route Rally Adding Fog Lights

BMWBMW Square Route Rally Replacing your stock brake light with an LED light Recent BMW’s monitor brake light current LED’s take much less current: 0.2A vs ~2A You must wire a resistor in parallel with the LED light to fool the computer into thinking you have a stock brake light Ohm’s law says R=V/I = 12/2 = 6Ω, can use 8Ω Remember P = V X I, so P = 12 x 1.5 = 18 watts, so you need a 20W power resistor

BMWBMW Square Route Rally Brighter headlights Even a small decrease in voltage to your headlight can dramatically reduce its light output: VoltageOutput 10.5V : 510 lumens 11.0V : 597 lumens 11.5V : 695 lumens 12.0V : 803 lumens 12.5V : 923 lumens 12.8V : 1000 lumens ←Rated output voltage 13.0V : 1054 lumens 13.5V : 1198 lumens 14.0V : 1356 lumens ←Rated life voltage 14.5V : 1528 lumens

BMWBMW Square Route Rally Brighter Headlights Consider running heavier wires in parallel with your existing headlight wiring to minimize voltage drop. BMW uses 0.75mm 2 (18ga) wire for headlights, causing ~1.2V drop in voltage Adding 12 ga wire in parallel to this will provide a significant increase in brightness.

BMWBMW Square Route Rally Tools & Supplies - tools Wire cutters Long-nose pliers Wire strippers

BMWBMW Square Route Rally Tools & Supplies - tools Get a Digital Multimeter –< $8 at Allelectronics.com Good crimp tool is an excellent investment –(try Starkelectronics.com) Soldering iron or soldering gun for heavy gauge wire

BMWBMW Square Route Rally Tools & Supplies - supplies Tap connectors are common: be sure to use the correct size for the size of wire – too small can damage original wire, too large will not make a reliable connection Heat-shrink tubing and a heat-gun will help make weatherproof connections

BMWBMW Square Route Rally ? ? ? ? Questions ? ? ? ?