6 or 12 volt battery system - normal voltage range when revving up?

Discussion in 'Motorbike Technical Discussion' started by 1970 Suzuki TS250, Jul 20, 2004.

  1. I have a 1970 Suzuki TS250 motorcycle. It has a 6 volt system.

    A guy ran my bike with a dead battery (it was dry, with no
    electrolyte) and this seems to have lead to burnt out headlight. I
    wonder if anything else should be checked.

    I added a new well charged battery, and when running at idle (with no
    lights on (I removed and still have replaced the headlight) I get
    about 7.3 volts. But when I rev up the engine to about 6000 rpm I'll
    get up to 9-9.3 volts. This seems high to me, but I would like to
    confirm with others.

    Questions:
    1. WHat is the voltage range on your 6 (or 12) volt system motorcycle
    at idle, engine revving (rpm?) without headlight and revving WITH
    headlight (lo) then (hi beam)? I assume 12V system divided by 2 will
    give normal ranges for the 6V system.

    2. What is a normal range?

    3. Should I run other electrical tests with the volt / ohm / ahm
    meter? to make sure I don't blow the next headlight? rectifier? I am
    not sure if this magneto equipped bike has a voltage regulator.

    The search begins for a 6 volt headlight replacement - the original
    Suzuki part has been discontinued.

    Thanks!
     
    1970 Suzuki TS250, Jul 20, 2004
    #1
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  2. A "12V" battery at rest should supply 2.2V x 6 = 13.2V. Typical
    voltage when alternator is running is ~ 14.4V. A 6 Volt battery
    has either three cells, or three pairs of bridged cells. I can't
    comment meaningfully on 6V charging systems.
     
    Michael Sierchio, Jul 20, 2004
    #2
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  3. I find it's generally a bit lower, especially on old bikes where the
    years have taken their toll of the connections and they're a bit
    corroded, increasing the resistance.

    Generally, 6.2-6.5v.
     
    The Older Gentleman, Jul 20, 2004
    #3
  4. 1970 Suzuki TS250

    mike Guest

    These bikes rely on the battery to take up all the slack in the system.
    A NEW, New, New battery will do that. After a few months, the voltage
    starts to creep up. A light blows out causing further stress on the
    others. "snowball" comes to mind.
    Make sure you get the right lights. Lamps with lower drain will
    overstress themselves and others.
    I got tired of spending $35 for a new headlight and another $25 for
    a battery every year on my '75 CB125S. I put a homemade shunt regulator
    on it and have had no problems since. Think of it as a power zener diode.

    mike

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    mike, Jul 21, 2004
    #4
  5. I would guess normal battery range ought to be about 6.3 - 7 volts max
    with the engine running. Above that and you're pretty likely to be
    boiling the battery dry.
     
    Rob Kleinschmidt, Jul 21, 2004
    #5
  6. Thanks for the replies so far folks - it is quite helppful. Other
    comments suggestions are still welcome.

    1. The older gentleman reported 6.2-6.5 volts. Has anybody else
    measured the voltage at the battery terminals with a voltmeter at idle
    and higher rpms?

    2. Tom suggested that the headlight might be similar to a Yamaha DT1,
    reporting that the headlight diameter on those were 5.5inches. On the
    1970-1979 Suzuki TS250 the sealed beam (discontinued) is 6V/25W/25W
    (at some point they went to 30W/30W), and unfortunately it is 6 and
    1/8 inch external diameter (with a horseshoe shape, ie flat bottom
    that was a Suzuki signature apparently). So the 5 1/2 may be a bit
    small. to fit in the bucket using the ring that holds it. Ideally a 6
    inch could be found, but 5 and 3/4 seems more common, or some
    aftermarket type assembly.

    3. Krusty Kritter gives a great review of the problem with early 70s
    charging system - I am getting acquainted with that. I'll try to get
    my hands on a TS250 1970 shop manual (the owner's manual does not
    specify anything about a regulator, and I sure haven't seen one yet!
    A cyber beer for you looks likely! The rectifier seems to do its job
    of converting the AC to DC, with infinite in one direction and very
    little resitance (about 50ohms) in the other direction.

    4. mike suggested that I'll be at risk as soon as the battery gets a
    little older... Glad to read about this - I would like to know which
    specific part you used to build your regulator, if you care to teach
    me - I could order them online from some electronics store (suggestion
    welcome) but I would need a shopping list and description to build
    this. Perhaps someone has put it on the web?. I think this is what
    the BAT-PAC http://battery-eliminator.com/ is, it retails for about
    50$+shipping. Mike also wrote "Make sure you get the right lights.
    Lamps with lower drain will overstress themselves and others." If the
    original lamp was 6V25W25W, does this mean that I can use a 6V30W30W
    safely but not a 6V20W20W safely? Do you happen to know if one or
    both filaments light up when the high beam is on (2 filaments would be
    50W draw right?).

    SO it looks like the best option will be to build my own 6V regulator
    and replace the battery with that (or do you leave the old battery in
    the system Mike?). I am not sure exactly what a "zener diode" is.

    Cheers!

    TS250 Suzuki 1970
     
    1970 Suzuki TS250, Jul 21, 2004
    #6
  7. Thanks for your further replies... I add some thoughts and more
    questions for the electrically enclined here, including one question
    for Mike and one for Rick (if they can elaborate on their previous
    post as per the questions below, unless someone else can answer.

    1970TS250 is an ENDURO-type single cylinder with a magneto flywheel.
    OK - noted. But the aim is not to help the ignition system, but to
    regulate the voltage in the night mode to prevent blowing bulbs. I
    found the specs for the 1970 TS250 in an original owner's manual that
    I ordered:

    Charging current at 2000 rpm in day mode (the circuit for the bulbs is
    open (off) in day mode, with battery charged and neutral indicator
    lamp (3Watts) turned on: 0.2A

    Charging current at 8000 rpm in day mode (the circuit for the bulbs is
    open (off) in day mode, with battery charged and neutral indicator
    lamp (3Watts) turned on: below 3.2 A

    Charging current in Night mode: no info shown just "--"

    Lighting VOLTAGE (use a fully charged battery) day mode (no info
    shown, just "--")

    Lighting VOLTAGE at 2000 rpm in night mode (the circuit for the bulbs
    is closed(on) in night mode, with headlamp (25 watts), tail lamp,
    speedometer lamp, tachometer lamp, neutral lamp turned on (3W): over
    6.0 Volts

    Lighting VOLTAGE at 8000 rpm in night mode (the circuit for the bulbs
    is closed(on) in night mode, with headlamp (25 watts), tail lamp,
    speedometer lamp, tachometer lamp, neutral lamp turned on (3W): BELOW
    8.5 Volts

    The above are specs from the book - I am waiting for my bulbs to
    arrive before I test the motorcycle. THe wiring diagram shows both an
    AC voltmeter around the bulbs and a DC voltmeter around the battery.
    Should I test either the DC or the AC (I am not sure if my ammeter /
    voltmeter will do AC volts) and this will yield the same values, or
    should those be different values? I noted that Rick reported:

    "From the manual for a 1974 Honda MT250
    Light off
    RPM 1000 5000 8000
    6.3V 8.0V 8.9V
    amps --- 1.5 4.1 measured from the positive battery lead to +
    battery
    terminal."

    But I wonder how the voltage is measured (in parallel, DC on battery
    terminals or in parallel AC on headlight wires?


    Krusty Kritter wrote
    But Mike had written:
    "These bikes rely on the battery to take up all the slack in the
    system.
    A NEW, New, New battery will do that. After a few months, the voltage
    starts to creep up. A light blows out causing further stress on the
    others. "snowball" comes to mind.
    Make sure you get the right lights. Lamps with lower drain will
    overstress themselves and others.
    I got tired of spending $35 for a new headlight and another $25 for
    a battery every year on my '75 CB125S. I put a homemade shunt
    regulator
    on it and have had no problems since. Think of it as a power zener
    diode."

    I wonder if Mike can comment if he uses a new battery or what he keeps
    instead?

    And if I don't make a shunt regulator, can I buy one and put it in the
    system? Where?

    TS250
     
    1970 Suzuki TS250, Jul 27, 2004
    #7
  8. 1970 Suzuki TS250

    mike Guest

    Nope, I use an OLD battery. That's the whole idea.
    Shunt regulator is just a BIG transistor on a heat sink with a smaller
    zener diode in the base. Since there's no way to turn it off, I had to
    put it after the ignition switch. I stuck it under the seat and tapped
    into the tail light wire. Since there's significant voltage drop in
    those old 6V systems, I just picked a zener that kept the voltage at
    the headlight within limits. The battery doesn't ever get fully
    charged, but I don't drive it at night, so I don't care. Just gotta
    have a light on in the daytime to comply with local laws. Headlight
    gets real dim when I step on the brake...but it don't burn out...

    There are issues. You could conjure up a situation where you put in a
    new fully charged battery and closed the ignition switch. LOTS of
    current could go thru the zener. In a practical situation, if you
    don't externally charge the battery, this shouldn't happen.

    If I were to do it again, I'd use a PIC processor and do the whole
    thing digitally.

    Best thing I can think of is to sell any 6V motorcycle to a collector
    and get on with more current technology...yeah right...
    mike


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    Compaq Aero floppy,ram,battery.
    FT-212RH 2-meter 45W transceiver.
    Toshiba & Compaq LiIon Batteries, Test Equipment
    30pS pulser, Tektronix Concept Books, spot welding head...
    http://www.geocities.com/SiliconValley/Monitor/4710/
     
    mike, Jul 28, 2004
    #8
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