Advertise on Bikeforums.net



User Tag List

Results 1 to 10 of 10
  1. #1
    meb
    meb is offline
    Senior Member meb's Avatar
    Join Date
    Aug 2003
    Location
    arlington, VA
    Posts
    1,745
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    battery in parallel with generator

    I used to have problems many years ago with a generator burning bulbs, especially once the first of the pair went.

    Wondered if putting a battery in parrallel would help.
    Would seem to have the added benefit of keeping the lights aglow when stopped.

    If it's high frequency spikes that burn the bulb, would putting a low pass Resistor-Capacitor filter in parallel with said battery solve the issue?

  2. #2
    Bill
    Join Date
    May 2007
    Location
    HIGHLANDS RANCH, CO
    My Bikes
    Specialized Globe Sport, Specialized Stumpjumper FSR Pro
    Posts
    630
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    First off you wouldn't connect a battery directly to the output without being sure it was designed for that. You would need some kind of a regulator circuit to adapt the changing generator output voltage to the charging requirements of the type battery you are using. And the battery in itself is essentially a low-pass filter to which the RC network would add nothing except loss and what 'high-frequency spikes' you talking about from a slow RPM DC generator? Without carefully matching the generator output to the specific battery you could under charge the batt rendering the whole project disappointing, or overcharging the batt reducing battery life and/or damaging the generator. Other for that it sounds like a good idea.

  3. #3
    Senior Member
    Join Date
    Feb 2007
    Location
    Stratford, New Zealand
    My Bikes
    2004 Mongoose Crossway 450, 198x Mitchells 7 Speed, 1990 Paul Dye Hand Built 7 Speed, 1965 Raleigh Sport
    Posts
    185
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    It depends on what the output of the generator is. The vast majority are AC output, which means you would first need to use a rectifier (4 diodes) to convert to DC. Most generators are 6 volt 0.5 amp rated, so a good match would be 5 1.2 volt nimh batteries. It should regulate the voltage reasonable well.

  4. #4
    Healthy and active twobikes's Avatar
    Join Date
    Mar 2007
    Location
    Caldwell, Idaho USA
    My Bikes
    mid-60's Dunelt 10-speed, Specialized Allez Sport Tripple, Trek 7.2 FX
    Posts
    887
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Some electric screwdrivers use only one diode to rectify AC current from a wall mount transformer for recharging the screwdriver's internal batteries. It is not real efficient because it wastes a good portion of the AC sine wave cycle, but it is cheap and it works. It would provide choppy current, which is better for battery charging, anyway. The four diode rectifier mentioned is called a bridge rectifier, in case anyone is unfamiliar with them and wants to search for an explanation on the Internet that would allow building one.

    An electronics book I have says batteries in parallel with another DC source have the effect of regulating the voltage. I have not tried it, but it sounds like it would work.

    I am not sure about how well a low pass RC filter would work to reduce spikes. It seems the spikes would be voltage spikes, not frequency spikes. RC filters usually reduce frequency spikes. You could always try it. All engineering principles were developed by trial and error at some point.
    Who am I?
    Where did I come from?
    Why am I here?
    Where am I going?

  5. #5
    Senior Member pmseattle's Avatar
    Join Date
    Jun 2004
    Location
    Seattle, WA
    Posts
    451
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by tspoon View Post
    It depends on what the output of the generator is. The vast majority are AC output, which means you would first need to use a rectifier (4 diodes) to convert to DC. Most generators are 6 volt 0.5 amp rated, so a good match would be 5 1.2 volt nimh batteries. It should regulate the voltage reasonable well.
    Bicycle generators are AC ? I always assumed they were DC with permanent magnets for the field.

  6. #6
    Healthy and active twobikes's Avatar
    Join Date
    Mar 2007
    Location
    Caldwell, Idaho USA
    My Bikes
    mid-60's Dunelt 10-speed, Specialized Allez Sport Tripple, Trek 7.2 FX
    Posts
    887
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I took one apart after it generated its last. Permanent magnets attached to the shaft spin. A thin piece of steel that looks like an asterisk has a web of wire for a coil laced around the arms of the asterisk out to about half of the length of the arms. At that point the arms bend upward inside the can that is the generator body. There is no commutator. Such a generator would just about have to be AC.
    Who am I?
    Where did I come from?
    Why am I here?
    Where am I going?

  7. #7
    Senior Member Fibber's Avatar
    Join Date
    Jul 2005
    Location
    Dutchess County, NY
    My Bikes
    Fuji S-12s, Trek Navigator 200, Dahon Vitesse D7, Raleigh Sprite Touring ('70's)
    Posts
    826
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by meb View Post
    I used to have problems many years ago with a generator burning bulbs, especially once the first of the pair went.
    I remember having this problem also as a kid, and finally came to realize that my replacement bulbs were not rated for the voltage (6v, IIRC). I think I had 4.5v (3D cell battery bulbs) in place. You can get away with this for a while when two bulbs are in parallel, as their capacity exceeds the max current output of the generator. So as long as you 'load' down the current, the voltage stays in check. Once one bulb fries from the slight overvoltage, the second one gets the full blast, and cooks shortly thereafter.

  8. #8
    meb
    meb is offline
    Senior Member meb's Avatar
    Join Date
    Aug 2003
    Location
    arlington, VA
    Posts
    1,745
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by twobikes View Post
    I took one apart after it generated its last. Permanent magnets attached to the shaft spin. A thin piece of steel that looks like an asterisk has a web of wire for a coil laced around the arms of the asterisk out to about half of the length of the arms. At that point the arms bend upward inside the can that is the generator body. There is no commutator. Such a generator would just about have to be AC.
    Sounds like they have been misnomerred-if they are AC they should be referred to as alternators.

  9. #9
    meb
    meb is offline
    Senior Member meb's Avatar
    Join Date
    Aug 2003
    Location
    arlington, VA
    Posts
    1,745
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by twobikes View Post
    Some electric screwdrivers use only one diode to rectify AC current from a wall mount transformer for recharging the screwdriver's internal batteries. It is not real efficient because it wastes a good portion of the AC sine wave cycle, but it is cheap and it works. It would provide choppy current, which is better for battery charging, anyway. The four diode rectifier mentioned is called a bridge rectifier, in case anyone is unfamiliar with them and wants to search for an explanation on the Internet that would allow building one.

    An electronics book I have says batteries in parallel with another DC source have the effect of regulating the voltage. I have not tried it, but it sounds like it would work.

    I am not sure about how well a low pass RC filter would work to reduce spikes. It seems the spikes would be voltage spikes, not frequency spikes. RC filters usually reduce frequency spikes. You could always try it. All engineering principles were developed by trial and error at some point.
    A low pass filter would cutoff spikes above a certain frequency. For a bulb, you just set a lower cuttof frequency.

    I had a car alternator with worn bearings that was burning up voltage regulars from its voltage spikes due the play of the rotor. Thought the bulb burnouts were likely a result of the generator putting out spikes over the bulbs limits.

  10. #10
    meb
    meb is offline
    Senior Member meb's Avatar
    Join Date
    Aug 2003
    Location
    arlington, VA
    Posts
    1,745
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Fibber View Post
    I remember having this problem also as a kid, and finally came to realize that my replacement bulbs were not rated for the voltage (6v, IIRC). I think I had 4.5v (3D cell battery bulbs) in place. You can get away with this for a while when two bulbs are in parallel, as their capacity exceeds the max current output of the generator. So as long as you 'load' down the current, the voltage stays in check. Once one bulb fries from the slight overvoltage, the second one gets the full blast, and cooks shortly thereafter.
    I had the correct bulb.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •