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Thread: 1978 R80/7 amperage question

  1. #1
    Nick Kennedy
    Join Date
    Nov 2011
    Telluride Colorado

    1978 R80/7 amperage question

    Hi Gents
    I've got a 1978 R80/7. It looks to me, from what I can gather, the alternator puts out about 20- 21 amps max.
    Question for those in the know:
    How many extra amps do I have at cruising speed for heated gear in a practical situation. I've got a new battery and everything else electrical wise is in good shape. I don't want to over strain the system as this ride is getting up in years.
    Thanks in advance
    Nick Kennedy
    Last edited by nickrides; 12-29-2012 at 12:20 AM.

  2. #2
    Registered User lkchris's Avatar
    Join Date
    Mar 2003
    Albuquerque, NM
    It's got a 280 watt alternator. Alternator output is not specified in amps.
    Kent Christensen
    '12 R1200RT, '02 R1100S, '84 R80G/S

  3. #3
    Registered User
    Join Date
    Jul 2010
    Tularosa, NM


    Snowbum says that you should be fine with using heated clothing on this machine.

    Personally, I only use my heated gear at highway speed, and I turn it off when I hit traffic. Probably not necessary, but I do it anyway.

    To-Hell-You-Ride (in winter) but this should make it a lot more bearable. Watch out for cold tire edges!

    Walking Eagle

  4. #4
    Registered User amiles's Avatar
    Join Date
    Jul 2003
    Murrells Inlet, S. C.
    The stock Airhead electrical system is often just barely adequate to run the machine sans accessories. The ultimate solution is to spend about $500.00 or so for an improved alternator/voltage regulator system. 32A 450W. This begins charging at a much lower RPM than stock.

    Less expensive would be to disconnect & clean every electrical connection on the machine, check the brushes for wear & the voltage regulator for function. This may gain you the full capacity of the stock system, which at the 20 A that you state is 240W. This occurring above 3,000 rpm. Below 3,000 very little is generated.

    A sort of fudge on the stock system is to use a Battery tender or other charger of it's type. This way you will start each ride with a fully charged battery. This gives you as much margin as possible should you be running at an electrical deficit.

    Use a good voltmeter to check your battery when you get home from a ride to see what's happening.
    Supposedly 100% charge is indicated at 12.7v 50% at 12.2v.

  5. #5
    Registered User
    Join Date
    Jan 2006
    Wisconsin and Florida
    "It's got a 280 watt alternator. Alternator output is not specified in amps."

    True but amps and watts are related so for example assuming you are getting the
    rated max output of 280 watts then divide by the voltage at normal running speed
    about 13.2v 280\13.2 => 21.2 amps in theory

    volts x amps = watts

    the real question here is how much heated clothing and by one or two people
    and how do you drive and do you have enough sense to turn this stuff off when
    you are standing or going very slow and do you hold the brake on while standing
    with extra brake lights installed etc and are you using a thermostat that operates
    the clothing overall at less than full rated demand.....

    Each individual will have a different answer to what is adequate

    In my case I almost always run 40 watt heated jacket liner in cool weather
    This jacket liner uses less current than the headlight
    Almost never drive in stop and go traffic
    Almost never drive faster than 60mph

    Absolutely never have any proplems with this heated liner + 55/60 watt H4 on a 180watt /5 bmw
    or on a 280watt /6/2 conversion or on a 200watt aftermarket alt on 1968 R60/2

  6. #6
    MonoRT MonoRT's Avatar
    Join Date
    Jun 2011
    Huntington Beach, CA
    I don't want to sound like I'm a salesman for Datel (I'm not!), but those little LED Datel volt meters that sells are great for tracking your battery and charging system. The LED job pulls very little current, is dead accurate and is quite waterproof. I wired one of those meters right to my battery with an in-line on-off switch. I keep the meter on whenever I'm riding and I'll turn it on in the garage whenever I'm wondering how my battery is doing.

    I have an RT, so I also have a Motometer volt meter, but, since it hooks up via an old wiring harness and is about as precise as an atomic weapon, it only serves as a "maybe OK/probably not OK" indicator. Since the Datel meter is essentially a small plastic block, you have a ton of mounting options with a faired bike and even a non-faired bike - you can use Scotchlock or something like that to just stick the meter somewhere where you can see it.

    At any rate, with a direct-to-battery meter, you can see right away what effect your speed and accessory load is having on the battery - no worrying about what MIGHT be going on.

  7. #7
    Registered User richardak's Avatar
    Join Date
    Dec 2007
    Fairbanks, AK
    I'm with MotoRT on the Datel voltmeter and I didn't even bother with a switch since the draw is about 8ma. I have the same 280 watt charging system and have found that when approaching a town, I will turn off the heated gear and the heated grips. But the stock system seems to keep up with both plus low beams when the engine is above about 3K rpm no problem. It's easy to see that on the voltmeter.
    1983 R100RT hacked w/Cozy Rocket My blog
    2012 Ural Patrol
    Airhead #10576

  8. #8
    Nick Kennedy
    Join Date
    Nov 2011
    Telluride Colorado
    Thanks for the input.

    Does anyone have a guess at the amps the R80 uses going down the road at speed...You know; ignition, headlight on low etc.. I'm trying to figure out how many extra amps, for heated clothing, I have to play with.

  9. #9
    Registered User jad01's Avatar
    Join Date
    Dec 2006
    Houston, TX or Portland, OR
    Oak had an article in the December Airmail pertaining to a /5, noting:
    • headlamp 60 watts
    • engine ignition 40 watts
    • lighting ~30 watts
    • brakes/turn signals/horn are negligible as they are short-term loads

    I would imagine that the /7 is comparable. I seem to recall that I've seen a more comprehensive list on the forum somewhere, but maybe this helps? For what it's worth, I run my Widder electric vest without any trouble (33 watts draw).
    '78 R80/7 and '84 R100RS (Blues Brothers), '86 K75C (Icy Hot)
    '90 and '93 Mazda Miatas (Jelly Bean and Red Hot), '97 Nissan XE PU (Mighty Mouse)
    '96 Giant Upland (big Kendas, baby!)

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