We get lots of question here asking do I need a bigger alternator?
How much current does my heater fan draw?
So I have put together a List below which is based on the Minis electrical system, all are rounded up to the next amp if more that 50% for ease of calculations
Side Lights Front and Rear 2amps
Dip Beam Headlights 9.16amps (55w Halogen Bulbs)
Main Beam / Flash Headlights 9.16amps (60w 10amps)
Indicators One Side 3.5amps
Hazard Lights 7amps
Stop Lights 3.5amps
Reverse Lights 2.5amps
Heated Rear Screen 10-20amps depending on the element
Dash Lights on Gauges and Indicator lights 2-3amps (Depending on auxillary gauges if fitted
Interiot light 0.4amps (5w Festoon) 0.8amps (10w Festoon)
Horn single 10amps
Heater Blower 6amps slow 10amps fast
Ignition Coil 12v 4amps
Cigarette Lighter 10-12amps
Wiper Motor Lucas 14w 1.5amps but stalled amps (frozen on screen/ seized wheel boxes,dry cable 4-6 times amps)
Number Plate Lamps 0.5amps
Spotlights (55w Bulbs) 4.5amps each
Normal Car Radio 3amps
Washer Pump 1.5amp but when rubber impeller swells 5amps on start
Parasitic Drain Immobliser/Alarm <150-300mA depending on model of system
Starter Solenoid 10-12amps
Starter Motor 150amps when cranking 180+ amps on Initial crank
Central locking Solenoid (each) 3-4amps Non Standard
Power Windows 20-25amps Non Standard
1000w Amplifier 85amps Aftermarket for High End HiFi System
Cooling Fans, I have only tested the Kenlow range of fans and they vary with fan size from 180mm Fan at 4.5amps to the 400mm Fan at 15amps, The Kit for the Mini has a 255mm Fan at around 6amps
Obviously and Motor with tired windings the amperage will increase.
So a Standard Mini driven at night
Sidelights/Numberplate Lights 2.5amps
Headlights 10amps
Dash Lights 3amps max
Ignition 4amps =19.5amps
2 Extra Spotlights 10amps =29.5amps
So if we keep all the above active and then add the blower fan and radio which is approx 10amps were getting very close to the 17ACRs 45amp output, or if you have the earlier model 17 ACR rated at 36amps your in trouble
And Lastly I Recommend That Every Classic Car Should Have A Voltmeter Fitted To Keep A Eye On The Battery Voltage ( Auto Electricians Must Know When Driving lol), Rembering That At Low Engine Revs and Idle Your Battery Will Be Supplying Voltage Back Into The Electrical Circuit, Until The Alternator Can Overcome The Electrical Draw.
All the other items like Indicators are momentary and add to the total amps but for a short period
