Topic: Getting rid of a battery, have you tried this trick?

[DammitDan]

I've got the perfect solution Nomad... and it only weighs 79lbs.

I shouldn't think you'd need a battery on this ULTIMATE CAFE RACER!

[Harry]

Stay awake out there, you OLD TIMERS! I've got some prune juice and geritol if you are having trouble getting off your "butty" to answer the questions!

 

NNNNNNNGGGGGGG!!!!

[Quail "Owner of the comfortable k8"]

sorry dennis,didnt mean to upset you.It was just a link to the battery eliminator people were mentioning.I made no comment on suitability for sohc or not.Asprin,a cup of tea and a nice lie down might be in order

Chrome tank

have you tried a suction cup to pull the dent from your tank, that and an air hose in the petcock can work wonders. (careful on the air pressure).

  Whos the girl in the picture, whats the story there?

 I thought Dennis was going to jump up and smack you with the keyboard for a minute there.

[bryanj]

I know Dennis well and he is having a REALLY bad time at the moment so its no wonder he occasionaly "bites". Harry BE VERY CAREFULL with the air hose idea I tried it years ago and yes the dent came out BUT the tank "spread and didnt fit the frame any more! And a s an old timer i just got to say ZZZZZZZZZZ

[Raul CB750K1]

Yeah Chrometank, who's the chick in the avatar? Is she the one that is sending you love messages through this forum?

Raul

[eldar]

I know what some say, "you have to use a battery". Well I say, try what you want. Modify the charge system if you want. Try banks of capacitors after all, a battery is similar to a capacitor anyways. Both absorb voltage spikes, both store energy although the average capacitor loses its energy faster the battery loses its energy over time also. The problem you have to over come is energy storage and supply.

Using the proper type and number of capcitors, a slow discharge type that stores a decent amount, a person could probably pull something like this off.

All I will say to those that crap on the idea is that, we would not even HAVE motorcycles if people had not experimented with ideas others thought impossible.

Remember, at one time the earth was flat and a person many considered a flake proved that it was round. 
Flight was only for birds but people challenged the idea and we have gone to the moon and satelites have gone out of our solar system.

[Bodi]

The better way to save weight is probably to use a small 12V lead-acid battery. If you're giving up electric start you lose several pounds immediately by removing the motor and solenoid, a tiny battery - even a gel cell - would do to provide starting ignition power and energize the field coil to get the alternator going. I would install an electronic regulator though, the mechanical thing is untrustworthy at best.
As has been mentioned a few times, the alternator can not be relied on to self-start. It might... there's some residual magnetism in the pole pieces - or it might not. Regardless, it isn't going to provide enough juice to fire the ignition at kickover RPM.
No high capacity capacitor known to me (these are all wet chemistry designs) will hold a charge for an extended time, there's always some leakage (in a battery too) and I think a cap would go dead in a day or two at best. An air gap plate capacitor in dry air or vacuum will hold a charge indefinitely, but even a few microfarads means a capacitor the size of a big refrigerator.

[TwoTired]

Well, I just did some back of the envelope calculations.

Assuming there is no electrical power generated from simply operating the kick start lever, there would be a need for a fully charged capacitor, at the ready, to operate the field coil and the stock coils.
The field coil is about 5 ohms resistance and two 5 ohm coils operating in parallel are 2.5 ohms for a total of 7.5 ohm resistance.  It is assumed all lighting and other electrical devices on the bike are switched off during engine startup. (No oil light, no neutral indicator… nothing.)

Further, lets assume it will take ten seconds to start the bike from switch on. And, we already have a fully charged capacitor installed, ready to deliver power to the two items required to get the beast started.

The formula for capacitor charge (and discharge) of an ideal capacitor is T= RXC.  Where T = time in seconds to discharge 63.2 % of its capacity.  R is the resistance of the circuit.  And C is the Capacitance.   However, below about 8-9 Volts the coils won’t have enough power to fire the spark plugs or stimulate the alternator.  So, we will double T, so the capacitor doesn’t discharge below a value useful for starting purposes. Let’s plug the data into the equation, converted to give us the result in C, which is:
C = R X  (T X 2)

Or,
C = 7.5 X 20
C= 150 Farads

So, there you have it.   Just put a 150 Farad, lossless, capacitor in place of the battery, wire a switch to turn off all lighting, pre-charge the capacitor and you have ten seconds to start your bike up and motor away.

Probably best to set your idle at 2500 RPM before you turn the lighting on.  So, the alternator will put out enough power to run the lighting, ignition, and field coil excitation.  You won’t be able to go below 2000 RPM or so for longer than 20 seconds (about) before the cap discharges too low to run or restart the bike.

Also, the stock regulator relies heavily on the battery to maintain voltage regulation in the system.  As mentioned by others, an electronic regulator will probably be needed to keep from frying bulbs and, perhaps, other devices in the bike.

Be sure to let us know how all this works out.  No charge for the engineering service.

Maybe "dar" will voluteer to come over and help with your experiments, invent something really great, make loads of money, and then laugh at all the stupid scientists and engineers that didn’t think of ignoring physics sooner.  Who needs an education anyway…

Good Luck!

P.S.  So, I went out to the garage and found a big capacitor.  It’s about 2 lbs, 3 inches in diameter and four inches long and is labeled 47,000 MFD.  Micro farad.  Let’s see… move the decimal six places to the left.  Ah, so it is .047 Farads.  So, I only need 3190 more of these to try this out!  Hmm, these things are about $4-$5 each, plus the trailer and hitch to add to the bike…

Um, maybe I’ll stick the the $30, 5lb battery.

[douglascoolgrey]

Is this a racing application? Could you start the bike by jumping from the battery?

[Bodi]

For racing you remove the alternator and starter then use total loss ignition; get a battery big enough to last at least 2X the longest race period you might encounter and keep a few of them charged up. When your race is called you (hopefully) have a fresh charged battery installed and you bump start the bike, stage, start, race, do your victory lap and ride back to your pit and shut down. NiCd batteries are pretty common, a small NiCd cell can put out an amazing amount of current - much more than an equal size lead acid cell.
There are (were?) magneto kits for the 750 bikes but I've never seen one for smaller Honda fours.

[eldar]

gee tired you sound so bitter about something. This has nothing to do about education, it is about intrepid spirit and the desire to try something new. Something you dont like to do, you dont even want to remove your points. Laws of physics have changed ever since people have studied science.  I wont invent something like that but someday someone will then what will you say? I bet you will have a hard time admitting you were wrong. At least I know I can be wrong but instead of giving up before even starting, I like to at least attempt things. It is called experimenting. Again without people like me who you want to bash, We would have only simple tools and nothing more.

Whatever tired. If someone wants to experiment, you have no right to say that it will never work and to belittle them.

Pushing the envelope is how humans have gotten to where they are now and if you can dispute that, maybe you should stop riding cause that is how you have come to have your motorcycle anyways.


But to overcome ignition issues, fit a magneto to the bike. That is how dirt bikes work. That will provide power for ignition and so capacitor would not be used for that.  If you are modifying the system, then you can fit this so that removes worrying about the charging system for ignition. If the engine turns, the magneto produces.

[eldar]

Sorry to rip that much but I see no reason to discourage someone against experimentation by talking down to them and basically calling them stupid. That is uncalled for. if you dont agree with it, then dont read or post.

[chrometank]

hey raul,yeh thats her.I got in trouble big time so ilm sorta making amends ! She certainly knows how to embarass a bloke.
cheers

Hey quail, my tanks got more dents than kirsty alleys thighs and getting more all the time,Ive let go worrying bout it.It  has a very nice worn in look about it 
cheers

[Raul CB750K1]

I agree with TwoTired this time. Even when I don't have so much spare time to make calculations or write long posts, a capacitor simply won't work. It's a law of physycs.

I don't think TwoTired want to discourage anybody to try. If you want to experiment, go ahead, but then why asking wether it would work or not? Just go ahead, buy the largest capacitor you can find and experiment.

It's like if my neighbour tells me he wants to experiment wether humans can fly just by throwing themselves out of the window. I don't remember well the laws of physycs that demonstrate it is impossible, but I got gut feelings that it won't work. But hey, if you want to experiment it will not be me the one to discourage you!!!! 


In my opinion the smallest 12V lead-acid battery you can find will do the work. You just need a well tuned-up bike and a little juice to give the initial coil excitation. But the battery capacity will be inversely proportional to the size reduction. How about getting rid of the alternator and fitting a 2-stroker magneto? That would be experimenting also, and you would have a completely autonomous and battery-free bike -this time I'm not being sarcastic-


Cheers

Raul


P.S. Hey Chrometank, I guess your chick is so proud to appear among this bunch of wrenchheads...

[Gordon]

All I have to say about this is that L.A. Nomad asked for opinions and responses, and opinions and responses were given.  So who's the one doing the bashing here?

And Chrometank, just from seeing the tiny image in your avatar, she looks worth it to me! 

[Harry]

MODERATORS REQUEST:

Some members have expressed concern regarding the tone of some of the posts on this thread, to which I am obliged to respond.

Gentlemen - we have a good thread here, with lots of good arguments for and against. Any argued view represents a valuable
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It is the relaxed atmosphere of this forum, the plethora of information and the genuine willingness to share that makes this one of the best bike forums on the net.

[Mark M]

I have pondered this for some months and have currently found no way round having a battery.
The one I'm trying is about 1/4 of the size of an OE one. It's a tiny 12V 3AH scooter battery, I also keep
a spare charged up to swap them round from time to time. It's under the seat hump in my avitar.
I dont have an electric foot or indicators, the lights are only to keep me legal and not for general use. So it's only
purpose in life is to keep the ignition up and running. The bikes just coming to the fine tuning end of the build, but as
winter is fast approaching here will not see general service until next spring,(unless I decide to fit a big bore kit which
will probably have it off the road for another year!). So I can't comment on the expected life of this poor little battery yet.

 

[eldar]

Harry I agree with you completely. I dont care if people are wrong or right. It is when they are rude about it for no reason.

My whole opinion is that if someone wants to try something, they can and that is fine and should not be discouraged.

maybe some WILL find a why to use capacitors or some other method and give us all something we can do that works better than original. 

This is something to be ENCOURAGED and supported not have physics that may be foundto be flawed in 10 years.

Always ask questions, You may not get the answer but the question will be there and someone else may get the answer.

Again I dont want to cause problems but we are all EQUALS here and should be treated as such.

[bistromath]

You can use a smaller battery but your idle time will be greatly compromised as you will be discharging between 7A and 10A at idle. So if you run a 3AH battery you will get between 20 minutes and half an hour before your battery is dead, at idle. If you are in stop-and-go traffic this can be a problem. To be honest, most people who muck with the electrics go the opposite route and run a total loss system where they take out the alternator completely. Gets you a significant weight reduction, snappier revs, and a little HP boost at the expense of only being able to run for an hour or so. =)

And TwoTired, I have a 2 farad cap on my desk that's the size of an Oreo. Problem is, it's only 1.2V rated, and discharges veeeeery slooooowly as its internal resistance is very high. =D

[eldar]

So bistro, if you were to combine a few of these capacitors, do you think it would run lights once the engine is running with a magneto ignition?  How much does the thing weigh?

[bistromath]

Hehe no eldar, for a couple of reasons. You'd need to string up a bunch of them (I'll take TwoTired's math for granted 'cause I'm too lazy to do it =D ) and the voltage isn't high enough. You'd have to wire them up ten in series, and like six in parallel... sixty Oreos.

Then there's the fact that they don't discharge quickly enough to pump the power you need them to. Even sixty of them.

Capacitors are not energy-dense, as a general rule. You're almost certainly much better off with a battery.

You know, come to think of it, if you REALLY wanted to strip some weight off, you could shell out for a lithium battery pack. You'd want three in series to give you between 9 and 12.6V (depending on the state of charge) and a four amp-hour lithium cell is about 4"x4"x1/4". And lithium cells will give you a reasonable amount of juice. You can get 20C discharge (C is the capacity, so a 20C, 4Ah cell can be discharged at 80A) cells for a small compromise in capacity.

That said, it'd be expensive, and would only save you five pounds or so. But it'd be pretty cool. Oh, you'd also have to replace the regulator with one that knows how to charge lithium batteries, since they need a pretty regulated charge cycle.

That might be a fun one to try.

[eldar]

well maybe they could run led lights but I suppose you still have the headlight. Someday maybe. I would like to try, hey you just never know! 

[Raul CB750K1]

If the cheat sheet I used to pass my Electronic Componets exam was right, capacitors store the charge by means of electrostatic charge. When the voltage is applied the electrons tend to group in the plates and there they remain. Increase the voltage and a spark will cross the gap like in a spark plug -in a nutshell- The thinner the dielectric the higher the charge, but the easier to perforate the dielectric.

So a capacitor can hold 12 V, but the amount of energy is low. Make a short circuit between the terminals and you will see a nice spark when electrons go to meet their fellow protons, and then nothing. Don't try to do the same with a battery. Batteries don't hold charge, they create voltage by means of chemical reactions. When the battery is empty an applied current reverse the chemical reaction so the cycle can start over again. It's a completely different mechanism. Well, now you will tell me I'm wrong because electrolytic capacitors also rely on chemical reactions. That's true, but only to create a very thin dielectric, thus the polarity cannot be reversed.

I really don't see the point to get rid of the battery or alternator. If it wasn't for my previous experience, I would bet my left testicle again that if you make an acceleration or high speed test with the same bike, with and without alternator and/or battery, nobody would be able to tell the difference. Let me think in Kg for a moment. A CB750 is 230 kg, I weigh 80 kg and say an alternator weighs 10 kg. Total weight= 230+80+10=320 kg, alternator is 3.1% of the total weight.  If a CB750 gives 67 ponies, it means a power to weight ratio of 0.209 HP/kg with alternator, 0,216 hp/kg without alternator, that would feel like an increase in 2 hp.  Sorry I've lost my cheat sheet for the Physics exam so I can't tell how to calculate work so as to calculate the improvement in acceleration, but I really feel the drawbacks exceed by far the benefits. You can always shave weight by removing grab handles, side and centerstand, fitting a 4:1 exhaust, a new seat, a smaller gastank, aluminium handlebar, sidecovers, starter motor, mudguards, chainguard. You can live without any of those things, but the alternator and battery are important.

Raul

[Quail "Owner of the comfortable k8"]

For 2 lbs you could just go on a diet.  I could shave 40lbs if I would shut this machine off and go do some excercise.

[bistromath]

Yar, but remember the alternator puts a load on the motor. So taking it off and running total loss gets you some fraction of HP extra.