Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Advice on regulating a 6V motorcycle alternator.

  1. Aug 17, 2009 #1
    I hope it is acceptable to ask for advice here. I am based in the UK and currently restoring a British 1964 Velocette LE motorcycle. It is fitted with electrical components made by the, now defunct, Miller Company (also British).

    The vehicle has a 6V 3 coil alternator with permanent magnets mounted on the flywheel. It is a former police bike and has an uprated alternator which does not convert well to 12V but is rated at something over 60W.

    Originally the bike just had a lead acid battery, a selenium rectifier and no regulator but the load was balanced by a very complicated 8 pole switch which switched in the appropriate number of coils depending on the electrical load required. This worked reasonably well with an open vented lead acid battery.

    I wish to fit a Cyclon 6V 8Ah sealed battery and understand that this will mean I must fit a regulator. My problem is that nobody seems to make a 6V regulator for an alternator. Podtronics in Texas make a 12V unit which will also allow conversion of the Lucas 6V alternator to 12V but, as mentioned, this is not advisable with my alternator. They also make 6V dynamo regulators.

    I have spent considerable time searching for a suitable device but have come to the conclusion I will have to build one. I have the necessary amateur skill to do so but really have no idea about the design i.e. circuit design and component values. I realise heat dissipation is important but the mechanics of that I can deal with.

    Any advice would be very gratefully received having spent interminable hours searching for a solution.
     
  2. jcsd
  3. Aug 18, 2009 #2
    Here is a very simple and inexpensive 6 volt to 12 volt DC-DC converter rated at about 10 watts:
    http://www.aaroncake.net/Circuits/6-12conv.asp
    Adding or replacing about 4 components could raise the output rating to 60 watts.
     
  4. Aug 18, 2009 #3

    berkeman

    User Avatar

    Staff: Mentor

    I'm not sure, but I think the OP wants to stay with the 6V battery and electicals on the bike. Otherwise, he could just convert over to a 12V system and use standard components.
     
  5. Aug 18, 2009 #4
    That is correct I do wish to stay with the 6V system.

    The owners club for this particular motorcycle has just lost the services of one of the members who had an in depth knowledge of this particular motorcycle's various electrical incarnations and regularly wrote articles for the club newsletter. I was in correspondence with him shortly before he died and he sent me graphs showing the outputs of the various alternators fitted to these bikes. He pointed out the appalling output of the higher power 6V police machine alternators if converted to 12V, the standard Miller and the Lucas 6V alternators converted satisfactorily.

    He did not go into detail about why this was so but was emphatic in not converting my alternator to 12V, hence my problem.
     
  6. Aug 18, 2009 #5

    vk6kro

    User Avatar
    Science Advisor

    Volkswagon beetles of about that era (up to 1965 anyway) used 6 volt systems and 6 volt regulators. They used DC generators with brushes and commutators.

    If you had a look around, like at this place:
    http://www.bus-boys.com/charging71.html#CHARGING
    you might be able to pick up an old regulator.

    These would be electromechanical (3 relays, I think) and you may need expert help (auto electrician) to get one working on your motorbike alternator.
     
  7. Aug 19, 2009 #6
    I did see that VW fitted a 6V regulator bt was unsure whether it was for a dynamo or alternator powered vehicle.

    The good news is that I have this eveniong been told of a source of solid state 6V regulator. I will know for sure tomorrow. In the meantime I thank you all for your comments and advice. I will report back with progress in case anybody is interested!
     
  8. Aug 19, 2009 #7

    Danger

    User Avatar
    Gold Member

    This would be a great time for Wolram to weigh in if he's available. (He's had a bit of difficulty with communication for the last while.) He's a collector of, and an expert in, English motorcycles. He's built some beautiful machines.
     
  9. Aug 19, 2009 #8

    berkeman

    User Avatar

    Staff: Mentor

    Can you please PM him this link, Danger? I agree.
     
  10. Aug 20, 2009 #9

    Danger

    User Avatar
    Gold Member

    I can't PM him, Berkeman, because my mailbox is full. For some reason, that negates transmission as well as reception. I will, however, attempt to e-mail him with a copy to Kia in case he can't receive his own mail.

    edit: I just realized that I don't know how to use the PF e-mail forwarding function, and I can't remember either of their real e-mail addresses. I did, however, leave him a message on his 'friends' board.
     
    Last edited: Aug 20, 2009
  11. Aug 20, 2009 #10
    If you plan to use the charger to charge a 6-volt sealed lead acid battery while running the motorcycle accessories, the charging voltage needs to be maintained between about 2.25 to 2.3 volts per cell, so a straight 6 volt charger won't work. Here are articles on lead acid battery voltages for charging:
    http://batteryuniversity.com/partone-13.htm [Broken]
    and another:
    http://www.powerstream.com/SLA.htm
    There are bucking (voltage reducing) switchmode power supply designs that can be bootstrapped; meaning that if the alternator output voltage is less than the regulating voltage, the circuit can be bootstrapped so that the output voltage equals the input voltage. This would allow powering all the motorcycle accessories even if the alternator voltage dropped below about 6.75 volts.
     
    Last edited by a moderator: May 4, 2017
  12. Aug 21, 2009 #11

    wolram

    User Avatar
    Gold Member

  13. Aug 21, 2009 #12

    Danger

    User Avatar
    Gold Member

    Thanks, Woolie. Nice to see you back in the circuit.
     
  14. Aug 21, 2009 #13

    wolram

    User Avatar
    Gold Member

    Thanks Danger, i found the site i wanted,
    http://www.leveloclub.org.uk/index2.htm
    This club is dedicated to the LE or noddy bike as we used to call them :biggrin:
     
  15. Aug 21, 2009 #14

    Danger

    User Avatar
    Gold Member

    Oh, man... when I see the word 'noddy', all that comes to mind is Slade, one of my absolute favourite bands. :biggrin:
     
  16. Aug 21, 2009 #15
    Today I collected a purpose made module from a supplier of parts for old motorbikes. In conversation he told me that he sells around 6 per year because most people convert to 12V. The unit appears well made but is of sealed construction. The whole thing is within a large finned heat sink which measures about 3" x 4" and I am assured will fit the bill.

    I do belong to the LE club which, believe it or not has a membership of around 1,000! They have been established for years and acquired engineering drawings and many special tools from Veloce when they went bust in 1971. They also run a comprehensive spares service which makes the LE very easy to restore and maintain.

    The LE was used prolifically by police forces during the transition from bicycles to Panda cars. It was felt too dangerous for riders to salute senior officers and so they would nod to a senior officer as they rode past. That is genuinely the reason they became known as Noddy bikes!

    velocette_le200.jpg

    Thanks again for all the contributions to this thread.
     
  17. Aug 21, 2009 #16

    Danger

    User Avatar
    Gold Member

    I can't say as I've ever seen anything quite like that before. It's very cool and very weird at the same time. The condition looks mint in the photo, though. Good job.
    Thanks for the explanation of the name.
     
  18. Oct 22, 2009 #17
    Nick

    I have just read your post regarding your LE Velocette. I have an early Valiant I intend to do something similar to you i.e. fit a Miller police alternator. The standard Miller unit gave a feeble 42 watt so the 80 watt of the police unit will give a welcome boost. However, I was intrigued by your remarks about how poorly the converted to 12 volt operation. Is this change over effected simply by add a second 6 volt battery and changing all necessary components or was a more sophisticated solution sought by rewiring the coils to 12 volt operation? I am not an electrical engineer so I cannot think why the Miller unit was so bad. Was the police unit already 12 volt.?
    If you haven't already got a 6 volt regulator I think Paul Goff can help you and he also sells 6volt quartz halogen bulbs but I don't know how you can fit the one he offers into the old British Prefocus headlight rim.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Advice on regulating a 6V motorcycle alternator.
  1. 4AAs not giving 6v! (Replies: 6)

  2. 6v & 12 v batteries (Replies: 20)

Loading...