An observation about rectifiers

[yoster]

Hello,

In the process of getting my charging issues sorted out, I've had the opportunity to try out a few different rectifiers. I thought I'd share my findings as it may prove useful for some.

I've noticed that there are two different rectifiers that are "plug-n-play" for this scooter.

Rectifier #1:cgi.ebay.com/ebaymotors/250cc-Gokart-Voltage-Regulator-Rectifier-Go-Kart_W0QQcmdZViewItemQQhashZitem2304d92c86QQitemZ150405196934QQptZMotorcyclesQ5fPartsQ5fAccessories

Rectifier #2: www.scooterdynasty.com/vrrectifierfor250ccengines.aspx

Those can be found at different places, but it gives you the idea.

I tried both the cheaper one from eBay, and the exact replacement from ScooterDynasty where I purchased my scooter.

When the two rectifiers arrived, I immediately noticed that the physical size was different. The cheaper had a heatsink that was maybe 60% the size of the direct replacement; it was a much smaller unit. That unit produced 14.6v at higher rpms, about 14v at idle, unless it was idling REAL low (lie it will do after the enrichener turns off but it's not totally warm yet), at which point it would go to about 13.6 until warm). When the fan would kick on, it would drop to about 12.1v.

I figured that was fine, but for fun, tried the other rectifier as well. The results were interesting! With the larger rectifier, I was able to get 17volts when revved up, and idle was about 14.4 volts. The fan would drop it to 12.7, or 13.2 if I was revving/moving. The larger rectifier also made my headlights visibly brighter as I revved up. This is HUGE for me, as it will prevent my battery from taking a major toll when the fan is running 90% of the time during the summer season.

So the answer? After some searching, I found that different rectifiers are rated at different wattages. I believe the smaller, cheaper unit may have been restricting some of my available power from the stator.

Just a heads-up for some of you 250cc owners. I know a few on here have purchased that $19.99 unit and may not be getting all the power they can get out of their stator!

I'll definitely be keeping it under the seat however as an emergency backup!

[earlwb]

Good find. Nice info.
Ok those are actually voltage regulators. There is a rectifier or diode on many scooters. The diode serves the purpose of allowing the headlights and tailights to only come on when the engine is running. generally the diode/rectifier is uisually a cigarette pack size heatsink like unit adjacent to the voltage regulator.

of course inside the voltage regulator is a three phase full wave bridge rectifier though. It converts the 3 phase AC to DC for the electrics. But they usually run AC directly to the headlights and tail lights. Which is what the diode is in there for. With the headlights off you get more battery power to start the engine with.

But yeah, in your case the go kart voltage regulator wasn't designed to handle the increased current requirements for a 250cc scooter. It might work better for a 150cc or 50cc scooter though. That radiator fan on the 250cc scooters can really suck down some amperes.

[cruiser66]

Jan 21, 2010 13:40:26 GMT -5 earlwb said:

Good find. Nice info.
Ok those are actually voltage regulators. There is a rectifier or diode on many scooters. The diode serves the purpose of allowing the headlights and tailights to only come on when the engine is running. generally the diode/rectifier is uisually a cigarette pack size heatsink like unit adjacent to the voltage regulator.

of course inside the voltage regulator is a three phase full wave bridge rectifier though. It converts the 3 phase AC to DC for the electrics. But they usually run AC directly to the headlights and tail lights. Which is what the diode is in there for. With the headlights off you get more battery power to start the engine with.

But yeah, in your case the go kart voltage regulator wasn't designed to handle the increased current requirements for a 250cc scooter. It might work better for a 150cc or 50cc scooter though. That radiator fan on the 250cc scooters can really suck down some amperes.

I agree with yoster's findings. I have exactly the same unit on my scoot with the same results. I will be replacing this with the CfMoto OEM style regulator/rectifier. The smaller unit is a good backup as long as you run only one headlight at a time. It will keep the battery charged at normal operating speeds even with the fan as long as you run leds and one headlight.

Your right earlwb, these are not rectifiers per se, but they also are not strictly regulators. They are both and are called regulator/rectifiers as they perform both functions. On the 250's the DC output of the regulator/rectifier not only charges the battery but also feeds all the light and accessory circuits. The only unit on the scoot which uses AC off the stator is the auto enricher which is tapped off one of the stator coil outputs. All three phases of the alternator or stator are connected directly to the regulator/rectifier and there is no separate coil for lights.

66

[earlwb]

On my 250, they tap off of the alternator to provide AC for the headlights and tailights. it is AC, not DC on the lights. The headlights and taillights only lite up when the engine is running. If the diode burns out then the headlights can stay on all the time, even if you turn off the ignition switch. Makes for a good symptom when it happens.
Yes you are correct in that the enrichener heater coil uses AC too. It also only gets heated up if the engine is running.

Now some scooters, may have the CDI and ignition coil grounded through the enrichener heater coil. If you unplug the heater coil on the enrichener and the engine won't start or appears to be dead, then that is what is happening.

[cruiser66]

The headlights on my scoot (YY250T) work the same way in that they come on only when the engine is running. The diode which is external to the regulator/rectifier acts as a blocking diode and not a rectifier. This diode is also known as a relay because it acts like a relay to connect the output of the regulator/rectifier to the battery once the engine is running if the output of the regulator/rectifier is greater than the battery voltage. When this diode shorts out, the headlights will stay on all the time even with the key off because the battery will be connected directly to the headlights, but if the diode opens up the battery will eventually die out when running the scoot because there will be no charging voltage on the battery, but the headlights will still work. The diode blocks the battery DC from getting to the headlights. When the engine is started, the DC output of the regulator/rectifier will charge the battery assuming it is greater than the battery voltage. If the output of the regulator/rectifier is too low, the headlights will still come on but the battery will not charge. The rectified output (DC) of the regulator/rectifier is what runs the headlights and instrument lights on my scoot. If the regulator/rectifier dies then you will have no headlights and, of course, the battery will eventually die. All other lights are fed from the battery.

66

[unclepablano]

You should never be seeing 17 volts on a 12 volt vehicles charging system. That is a defective regulator. 15 volts would be considered borderline. Excessive voltage will cook your battery and your headlight, causing premature failure of both.