A few simple questions.

studiot

Joined Nov 9, 2007
4,998
Reading through this thread there seem to be some rather confusing statements.

No one seems to have addressed the issue of AC v DC.

I very much doubt your bike runs on AC. It may well have an alternator, but the alternator will be configured to produce a unidirectional output.

If the power is truly AC then discussion about 12V v 13 V v 14 volts is fatuous.

Secondly LED is short for light emitting diode. A diode is another word for rectifier.
So an LED specified for 12v will operate perfectly happily on 12v AC, 12v DC or 12volts unidirectional output from an alternator.
The voltage spec for any diode/rectifier is known as the peak inverse voltage PIV and describes the maximum reverse (off) voltage the diode can block. The forward (on) voltage is defined by the diode and will be around a couple to a few volts.
The current in the on mode needs to be set (limited) by an external component as the diode cannot do this for itself. However I would imagine your tail cluster contains such components.
 

Thread Starter

dustiin

Joined Jan 13, 2010
60
From another popular forum (Thumpertalk) everyone has informed me that my particular bike runs on AC current. I also cannot find a rectifier anywhere on the bike and my voltmeter says it's AC current.

The issue with the LED from what I've gathered on this thread is the LED needs DC. But if you say it will run on AC and DC I'll go ahead and try. Since it seems like a light emitting diode would work with AC since it is an AC. I'll hook the LED up to my bike and see if it runs.

Why would the talk about the bike being 12, 13, and 14v be fatuous? Is it because it's not always the same voltage?
 

studiot

Joined Nov 9, 2007
4,998
Why would the talk about the bike being 12, 13, and 14v be fatuous? Is it because it's not always the same voltage?
Because 12 volts AC is nothing like 12 volts DC.

From another popular forum (Thumpertalk) everyone has informed me that my particular bike runs on AC current. I also cannot find a rectifier anywhere on the bike and my voltmeter says it's AC current.
Whilst the lighting might well be able to run on AC, the ignition cannot. Nor can any electronic control or other circuitry.

Please explain exactly what you meter reads when connected through a capacitor. On both the AC and DC scales.

I think you should research the bike specs a bit more thoroughly. Many automotive alternators contain internal rectifiers/voltage regulators.
 

Thread Starter

dustiin

Joined Jan 13, 2010
60
Yeah. I know the CDI is DC current for the ignition. I have researched and asked questions all over Thumpertalk and google. I will tell you what the meter says when connected through AC and DC, However I am still waiting for a new waterpump gear so it will be a little bit before I can say.

I 99.9% that most alternators contain internal rectifiers and voltage regulators, However I am very quite sure my bike is AC. In the manual it wants me to test a lot of connecters/wires with AC current.

I know 12v AC is not like DC 12v. But aren't they still both 12volts? Or maybe AC current is always showing different voltage readings. I don't think there's any caps on my dirtbike to connect a meter to. I'll search whenever I can but I have yet to see any circuitry, just wires and connectors and a voltage regulator.
 

Audioguru

Joined Dec 20, 2007
11,248
The max reverse voltage for most LEDs is 5V so 12VAC will cause them to fail without using a rectifier.

12VDC is not the same as rectified 12VAC. Rectified 12VAC has an average full-wave rectified voltage of 9VDC with a lot of flickering. Adding an output capacitor to the rectifier produces 15V which is too high.
 

Thread Starter

dustiin

Joined Jan 13, 2010
60
So I can't directly hook them up to my AC system cause they will fail and putting a rectifier on it won't work. So what do I do?
 

Audioguru

Joined Dec 20, 2007
11,248
You bought a cheap Chinese light without any spec's.
It probalbly will not work properly on your bike.
You could convert the electical system on your bike to a 12VDC system with lots of electonic parts, or use a 12V battery to power the light.
 

Thread Starter

dustiin

Joined Jan 13, 2010
60
The part is from Australia. $54 isn't too cheap. The specs were there, just didn't say how many amps it drew and no I have not bought it yet. I expect to be hooking up these blinkers that I already have too and they're LED... Maybe I need to toss a good sized DC rechargeable battery in the airbox with a battery tender or maybe it will just work on AC. I'll see.
 

retched

Joined Dec 5, 2009
5,207
If you are looking to add modifications to your motorcycle, (electronic mods) then you would really want to add a battery. If you try to use AC with the requested parts, you will have problems.

For example, with AC, you will get fluxuations with the REVs of the motor witch will cause things to act funny. If the blinkers are using relays, you will not be able to guarantee under or over current problems, both of which can cause problems. like FIRE. (You dont want fire on a bike)

Using a rectifier with your AC to convert to DC to charge the battery will work. Then you can power your devices with the battery. For the devices you want to use, you could use a three or four 9v rechargable batteries. The Lithium Ion type would give you plenty of usage for blinkers and breaklights.

Make sure you use a charging circuit for Li-Ion. This will REGULATE the voltage to your systems.

The plus of doing it this way, is the size of the pack. You would only have to find an area on your bike to mount the device the size of a pack of cigarettes. (maybe 2)
 

Thread Starter

dustiin

Joined Jan 13, 2010
60
That sounds like a good ideal. I'll have to trace the wires back to the stator to try to find which one is hot. I'll place a good size li-ion 12v battery in my airbox and then add a simple rectifier to the stator's hotwire.

Will I have to just run a line from a hot wire to the + on the battery then ground the - to the bike? If I bought a little regular 12v li-ion battery would it maybe have it's own charging circuit built in?
 

Audioguru

Joined Dec 20, 2007
11,248
A 3-cells Lithium battery is nominally 11.1V and is fully charged at 12.6V. The charger is separate and might need a higher input voltage that you have.
 

Thread Starter

dustiin

Joined Jan 13, 2010
60
I'd pick a 3 cell battery over a bigger battery but will my bike's stator connected to this battery (rectified to DC) be able to give the amps when the battery cannot make it at times?
 

Audioguru

Joined Dec 20, 2007
11,248
You must use a charger circuit with a lithium battery to stop it from exploding into very hot white flames. Some charger ICs allow the load to be powered from the source (your rectified alternator) while charging.
 

Thread Starter

dustiin

Joined Jan 13, 2010
60
I'll definitely need a charger IC that can allow load to be powered from the source and charge it too. Time to google.
 

retched

Joined Dec 5, 2009
5,207
Here is a OTS design for a small lead-acid battery and charger. It converts ac to dc then charges the battery pack for your use.

http://www.batteryspace.com/back-up...abatterywithbuiltinsmartchargerinbeltbag.aspx

This will allow you to visualize your design. You may want to purchace a small sealed-lead-acid battery like this one. Its better than having Li-Ion burst into flames.

[ed]
Remember to incorporate a happy voltage on/off circuit in your design. This will help keep the battery from over/under charges. If you just kept pumping power into a full battery, well, its not good for anyone.
 

Thread Starter

dustiin

Joined Jan 13, 2010
60
Input: 100 - 240V AC at 1.5A Max.

the amps on my bike are much higher then 1.5amps.

and this is only 6volts, won't I need a 12volts battery?

 

retched

Joined Dec 5, 2009
5,207
I was just showing a design idea.. and no, you can use any voltage battery. Just be sure to get the right charging circuit. If you use a 6v battery, you need a voltage doubling circuit to run the 12v equipment.

Input: 100 - 240V AC at 1.5A Max.
That is for the charger, not the battery

If you can get a good deal on a battery, a few components will make it work.
 

Thread Starter

dustiin

Joined Jan 13, 2010
60
Okay, when I get this 12v battery if it...let's say puts out 7amps. Will the rectified DC current going to the battery help give the battery more amps to run all my lighting and devices?
 

retched

Joined Dec 5, 2009
5,207
the leds run on milliamps. They would last a long time before the battery died. If you use a charger that converts from AC to DC, you wont need rectification. Or, if you have a rectifier, find a charger that works from a cars cigarette lighter plug. You can go from rectifier to the input wires on the charger to the battery.
 

Audioguru

Joined Dec 20, 2007
11,248
If the max current from a battery is 7A then charging it allows it to provide 7A for a fairly long time. The 7A from the battery can be added to the current from the charger to produce more than 7A but then the battery is not charging.
 
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