"Low voltage LED indicator" help - any electrical engineers out there?

Discussion in 'Thumpers' started by John E Davies, Dec 16, 2005.

  1. John E Davies

    John E Davies Runs at Mouth Adventurer

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    Hi - I ride a dual sported 2005 525 EXC and it's set up with a newly-rewound single phase stator (18 gage over-wound poles, full dc conversion with 150 watt reg/ rectifier) and LED tail light, and I am in the middle of making a custom wire harness for it. I want to be able to run an Aerostitch Kanetsu electric vest and thermostat - the vest draws 45 watts/ 3.3 amps at full heat setting, and less at lower settings. I haven't been able to do a full-load current test on my charging system yet because the harness is incomplete, but I am pretty sure that the vest will either be a little too much on "High", or max it out.

    Since I would only use the vest when droning down the freeway, the system should be able to handle the load, but I would like to be able to monitor it so I don't flatten the battery.

    I would like to fabricate or buy an LED low voltage light to mount on my stock computer mount. Ideally the light would ONLY illuminate at 12.8 volts or below, and be a very simple design - I just need to know whether the battery is charging or discharging. I already have an old blue LED HI-Beam Indicator (Sicass Racing) that I would like to adapt if possible - it mounts very neatly in the left hole. I can do simple soldering and fabrication from plans, if Radio Shack has a chip that can do the job.

    Any ideas or links? Any existing plans/ drawings or off-the-shelf device avaiilable? I think this would be a valuable addition to any EXC, as they are in the habit of draining the battery when used with a radiator fan and un -modified stator.

    BTW, I am working on a full write up including drawings and pics of the stator rewind, which I will post on my website when I am finished with the project.

    Thanks very much.

    John Davies
    #1
  2. Arch

    Arch Incurable Gearhead

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    John, go here for your LED battery voltage monitor. I've seen mention of the DC conversion mod before, but never paid much attention to it as mine runs a heated vest just fine and, besides a full heated jacket on occasion, that's pretty much all I need. Well, it also runs a 276c, but that draws nothing. I also have the factory thermostatically controlled fan and it's no problems on the hottest of Texas woods rides, even with the lights on. So I'm wondering why the switch to DC is needed? Looking forward to your write-up & pics. :thumb
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  3. John E Davies

    John E Davies Runs at Mouth Adventurer

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    That was a fast reply! That device would work, but it is not exactly what I am looking for.

    [​IMG]

    As you can see - the green light operates from 12 to 15 volts. I am hoping to come up with something that will ONLY come on below about 12.5 volts. I think the 3 volt range of this thing is too wide to be of much benefit. Maybe I am not thinking clearly..... I just want a light to come on to say "Hey idiot, your battery is draining!" I don't want or need anything more.

    I am really surprised that your stock EXC will run a vest - it must not draw much power. The stock system runs the lights off the A/C from the stator without rectification. The battery has 2 amps DC available through the stock KTM regulator/ rectifier for charging, and that is it in terms of DC power. Your vest will run "sort of" off AC at the expense of your headlights dimming severely. The vest I want uses well over 3 amps.

    As far as the mod: I wanted a pure DC system for steady lights at low rpm, no dead battery when running in the woods with the fan operating, and the ability to run a HID helmet light or vest. (If you get stuck in bad terrain and do lots of starts with the fan running, your battery WILL go dead.) The basic DC mod is simple and inexpensive and highly recommended. I opted to completely rewind the stator with larger wire and extra turns for additional output. Search for "float the ground" or ask if you want some more info.

    John Davies
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  4. Fariborz

    Fariborz Adventurer

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    You can buy one of these:

    http://store.cd4power.com/cgi-bin/cd4power.storefront/43a306ab005c75c427210c9f89420685/Catalog/1042

    and run it through a relay that is powered by your ignition key. This way it will only run when the ignition is turned on.

    Another option is one of these, that gives you more than just voltage:

    http://www.casporttouring.com/store/merchant.mvc?Screen=PROD&Product_Code=14124&Category_Code=Electronics

    But these are not waterproof and if you install them you need to make sure they are mounted somewhere that water cannot get to it or come up with a way to make it water proof using silicone or put it in a sealed plexiglass box.

    -Fariborz
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  5. Arch

    Arch Incurable Gearhead

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    I mainly use the bike for dual-sport stuff, John, so it could be 'cause I run with the lights off most of the time (it has KTM's Euro head/taillight switch). I saw in the manual that it made 150 watts and just never gave it much more thought as it seems plenty. Oh well, like I said, looking forward to your write-up. I'm always willing to fiddle with an upgrade! :D
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  6. CoolCarbon

    CoolCarbon By the Tay

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  7. bmwhd

    bmwhd God Bless Texas

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    I put one of these on all my bikes. Helps you monitor the load in a very simple way.
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  8. John E Davies

    John E Davies Runs at Mouth Adventurer

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    That is pretty much what I was thinking of. However, I still don't understand why the amber comes on below 12 volts. A charged battery is several tenths more than that - maybe they are trying to acocomplish something different than my goal - they are trying to warn that the battery is getting low.

    I really am looking to get a warning that I am exceeding the charging capacity of my stator, so a digital ammeter would be an ideal solution, but that is much more complicated, involving a shunt and complicated gage arrangement. Same situation really, but a different approach to monitoring what is happening...

    Thanks for the link - I may end up with The Battery Monitor if I can't come up with something more specific to my need.

    John Davies
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  9. Hair

    Hair no wants or warrants

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    If you go to a basic circuits or physics book you can find a current divider. Or current limiting circuit. If you set up one of these you can limit the current to your vest. Then your worries are over.
    #9