capacitor vs. battery

[snowskater101]

im making my yz street legal so i went ahead and bought a moose lighting coil that puts out 60 watts they say, but i dont know what to use to store electricity. ive read you can use a battery or a capacitor but i have no idea which would be better.

does anyone know which would be better and why? thanks

 

[snowskater101]

oh yeah and if your advice is to use a capacitor... how many farams(i think this is how to spell it) should i get?

 

[Rich Rohrich]

Using a capacitor to store power for this type of application isn't practical. You need a battery.

 

[snowskater101]

why do you think its not practical? im not doubting you or anything, i just dont know the first thing about capacitors or really even batteries. :whoa: ok i know some things about batteries but not enough to know which to use

 

[_JOE_]

A capacitor is not designed to store as large of a reserve of energy. They are more commonly used as a way to smooth out or sort of regulate the flow of electricity. You want something with a decent reserve capacity so, should you need to put a load on the electrical system that the charge coil can't keep up with everything will continue to function properly. Just get a battery and call it good.

 

[ZOMBIE666]

Capacitor is used as a battery replacement on bikes like RZs and such because the electronics (CDI/PV controller) dont like the crappy DC put out by the stator/rectifier alone; like joe said they are just used in this application to smooth out choppy DC. Youre just need it for lighting (and non HID at that) so you dont really need electrical storage at all unless you want to be able to run the lights with the engine off or to get rid of headlight dimming at idle. If you do decide to go with a batt. you will need a DC regulator/rectifier as well.

 

[Rich Rohrich]

i just dont know the first thing about capacitors or really even batteries.

I never would have guessed. ;)

 

[rmc_olderthandirt]

Hmmm... I believe that in California the requirement is that the vehicle must be able to operate the headlight for ten minutes with the engine off.

60 watts at 12 volts is 5 amps.

the equation for a capacitor is i=C(dv/dt) , where dv/dt means the change in voltage over a change in time.

A reasonable voltage range would be 14 down to 10, so dv=4. The change in time is ten minutes, or 600 seconds, so 5amps = C (4/600)

C = (5*600)/4 = 3750 Farads.

I think that such a capacitor would be about the size of the truck that you might carry the bike around in.

I recommend using a battery.

Rod

 

[_JOE_]

Ha, that's what we needed Rod! Some math! I had a 1 Farad cap on my amplifier and it was about 10 inches tall and 3 inches around. Even finding a place for that on a bike would be difficult, lol.

 

[VintageDirt]

Super caps, Ultra caps, Capatteries, Batacitors all can offer "battery like" performance but batteries may be more economical and certainly more available. High tech lithium ion batteries are light weight with an astounding power density but still, small sealed lead acid cells have proven themselves in the very application you're looking at. Seems a simple choice really. But then I'm no expert.

 

[dirt bike dave]

Street legal requirements vary dramatically from state to state. When the OP finds out what state he lives in, an informed person may be able to tell him if a battery is required to get a plate in that state.

I believe in CA, the battery requirement is so that the tail light can remain lit for an extended period with the motor off (I thought 20 mintues, but can't remember the exact figure).

For the dual sport bikes I've done in California, the state required a certified lighting inspection station to sign off that lights worked. On mine, the certified lighting inspection station (a motorcycle repair shop) always checked for the battery, and for tail light operation with the motor off. Other states will differ.

 

[snowskater101]

thanks for all the help and info. ill definitely go with a battery now that i know all this. i just got a dual 35w headlight off ebay that im going to use instead so maybe i won't be running out of juice quite as fast.

by the way i live in oregon and the yz250 is going to be 25 years old which according to the law, means i don't have to meet equipment standards or emission standards. i was told by a lady at odot that all i need is the title, a headlight, and taillight and i can make it street legal. however with this setup i can only ride it in good visibility(no night riding or fog ect...) im definitely putting signals and a battery on it though, the last thing i want is to be stranded on the side of the road with no lights.