Topic: This Could Be A Trick, I Guess, Anybody Tried It?

[bill440cars]

      Wondering if the "Battery Eliminator" could still be bought. Googled "Battery Eliminator" and came up with this from KawTripWorldwide. Comments anyone?

         http://www.kawtriple.com/mraxl/tips/battelim.htm


      Anyone know, right off, how big this capacitor would be, how much they cost and a good place to get one?

                              Later on, Bill

[Jheart]

It seems like these guys pretty much covered it. http://www.thumpertalk.com/forum/archive/index.php/t-635119.html
They decided it really only helped at idle, and that most of them were unable to run their blinkers. Plus I'm pretty sure it only works on a DC circuit.

They do cover finding your own capacitor on their forum:

"Go for at least 10,000 uF and 25 volts. More uF is better than less. Same for the voltage. Just get what ever fits well. It will make the tail/stop light work a little better at idle."

...and I dug up a couple from google shopping. They go for 25 to 40, for just the capacitors.
http://www.google.com/products?hl=en&q=motorcycle+battery+eliminator+capacitor&um=1&ie=UTF-8&resnum=4&sa=X&oi=product_result_group&resnum=4&ct=title

[bill440cars]

      While I appreciate the input, I have no intentions of running any lights on this particular project. It will be strictly offroad and my only need will be to enable me to run the engine off of the ignition system and not have to have a battery to keep up with, which will allow some more weigh loss. From what I gathered, from the link I provided, I could do what I need with a proper capacitor (if I couldn't get hold of an actual "Battery Eliminator".

       http://www.kawtriple.com/mraxl/tips/battelim.htm

    For easier reading, here is the info that is at the above link.


                             Battery Eliminator

Tired of replacing the battery or acid leaking on your pipes?  Replace it with a 50,000-mfd, 16VDC computer grade capacitor.

What to do:

   1. Remove battery.
   2. Wrap capacitor in ¼” to ½” foam sponge rubber extending over each end of capacitor and tape it so it will not come off.  The foam should be thick enough so the capacitor is a snug fit in the battery box.
   3. Connect the black lead (-) to a clean tight ground.  Remove paint and use serrated washer under ground lead bolt.
   4. Connect the red lead (+) as the battery hot lead was connected.

Installation test:

   1. Turn lights off.
   2. Start bike and run for at least one minute.
   3. Turn bike off.
   4. Turn ignition on, neutral lamp should light for 5 to 15 seconds.  (Capacitor should hold this charge for days)

System check with bike running:

   1. Connect voltmeter across ground and capacitor hot lead.
   2. At 1500 RPM or above, voltmeter should read 13-15 volts with a steady meter, that is, the reading should not change or bounce around.
   3. With the lights on, voltage should be 12 volts or above if RPM is 1500 or above.
   4. At 1500 RPM or below, voltage will drop if turn signals or brake light are used.

Note:  If voltage readings at 1500 RPM are above 16 volts or below 12 volts, the voltage regulator is probably defective.  This also causes short bulb life.

The battery eliminator solves a number of problems:

   1. Battery acid leaking on pipes, wheels, etc.
   2. Frequent battery replacement due to vibration.
   3. Elimination of battery weight.
   4. Voltage swings of defective battery resulting in weak spark, CDI failure, light failure, etc.

Disadvantages of battery eliminator are:

   1. Lights won’t work if bike is not running.

                 
       Seems like it would work real well for what I'm looking for and, might be the answer for some, building for the street, if the electric starter isn't used.
       

[TomC]

Hi Bill440cars
     I have been playing with a battery eliminator for my Honda Super 90. I copied the plans for it from the S90 yahoo group website. A very simple circuit and the parts were cheap.
     Does your SL360 have a permanent magnet rotor? Is it single phase or triple phase? My guess is that if all you want to do is run the ignition that all you need is a bridge rectifier and a big capacitor. About $5 at my local electronics surplus store.
          TomC in Ohio

[TwoTired]

Given this is an SOHC4 forum, and all our bikes have field coils in the alternator that must be excited to make power.  The battery eliminator has little chance of usefulness.

The 4.9 ohm field coil of the smaller bikes draw 2.5 amps, the 5 ohm coils draw about the same.  So, even if you rewire the bike so ONLY these two circuits are powered, a capacitor will drain pretty fast after you switch on the key.

The math:
one ignition coil, about 5 ohms
one field coil, about 5 ohms
These two loads are wired in parallel, resulting in a 2.5 ohm load offered to the power supply, which in this case is a charged capacitor.
Assume a 50,000 microfarad cap is charged and holding 12 v.  The discharge rate is determined by the formula ;  T (time in microseconds) = R (resistance,ohms) times C (capacitance in microfarads).  In this case T = 2.5 x 50,000 or 125,000 microseconds (10 ^-6).  In seconds, that is 0.125.  This is the time it takes to reduce this cap's charge to 37 percent, or 4.44 Volts, which isn't near enough to spark the plugs.  About 10 V is needed to spark the plugs or about 80% of the full cap charge.  It takes about 10% of the RC time calculation to reach the 20 percent discharge level (the discharge rate is NOT linear).  For these particulars, that's about 0.0125 seconds to drop the cap voltage from 12V to 10V.
So, you better be quick between the time you turn on the key to when you kick the bike, and hope it starts on the first kick. 

Large capacitors aren't perfect, and often have leakage properties.  This means that they will eventually equalize and lose their charge eventually, even if they aren't connected to anything.  How long, depends on the quality of the capacitor.  Better quality means more money, usually.

If you want to use a capacitor instead of a battery, then you need a bike with a permanent magnet in the alternator, so it will make power during kickstart and bring the Capacitor up to a voltage that will spark the coils/plugs.

Cheers,

[eldar]

Bill, just fit a magneto to that sucker! Never need a battery then! OR a capacitor!

Ran my yamaha like this years, some with my old honda trail 70.

[bradweingartner]

I have some tiny Sealed lead acid batteries that would probably be as close as you could get to a eliminated battery on an excited alternator bike.

2.3Ah Approx 7" long x 1.25" deep x 2.25" Tall.

I plan on trying one out on my Kick-Only CB550 when it's done.

[DsKing416]

I use a sealed lead acid battery that is 12v and 2 amp made for a computer and it's about the size of a deck of cards and weighs less than that capacitor. I have my headlight wired solid so I can't turn it off but I also have it wired after the rectifier so it only gets power from the rectifier, so no need to worry about when it's on because it can't be unless the stator is producing charge. Works great. I changed to a modern rectifier regulator (I took it off a four wheeler) also no adjustments just the right charge all the time.

[DsKing416]

We've all gone through what you are doing in your head and we are just sharing what we've learned. The capacitor can work if wired correctly. I chose the more predictable battery. I mean lose the harness, it's not difficult. Start over and go one part at a time. Solder and heat shrink everything, less power loss that way. You have lighting, coils, stator, rectifier, regulator, and a battery. Use the stator as a firewall for the lighting, it can't bridge the gap. Wire the coils#1 stator#2 rectifier#3 Lighting#4 A one way solenoid facing to the battery (radio shack or better)so it gets the left over (I run a computer Pc3 and fuel injection with this setup)#5 battery#6

It works for me. Don't forget a fuse after the rectifier.

[racer69]

Cycle x has a setup for no battery and it makes more power.
Less magnetic pull= more power.
even comes with a plug for the starter.

Just more food for thought!

[5Dave]

Given this is an SOHC4 forum, and all our bikes have field coils in the alternator that must be excited to make power. 

Thanks for the info. 

I just acquired a very sweet '76 CB550 and didn't understand why kicking it wouldn't start it - until I saw another note that said you need a battery, and then yours, which explained why. (now where's the "thumbs up" or "clapping hands" smilie )