AC to DC Rectifier/Regulator Ground Question?

#1
Hello,

My understanding of the grounding of lights, etc powered by an AC rectified to 12v DC using a battery, is that those grounds need to go back to the negative battery post, and not grounded to the frame.
My question is, what about things that already ground through the frame like the headlight, taillight, horn button, etc?

Do I need to insulate those items from the frame, so that they are no longer grounded through the frame?

Thanks
 
#3
It’s a Tecumseh with 2 single outputs.
I know the rectifier has 2 AC inputs and gets grounded to the frame and has single 12v+ hot lead
 
#4
That is the outlier case. you can't use a full wave rectifier. I built this unit using two inline diodes for each leg then connecting them together. I then. used a cap to smooth the DC. I used it with led bulbs that have no issue with it being unregulated but some led bulbs can't take to high a voltage.
 

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electrathon

Active Member
#5
It is always best with everything to ground to the battery. That said, if you have items like lights that ground to the frame you can ground the neg of the battery also to the frame or run a ground wire from the battery to the mount tab on the light. It will make no functional difference.
 
#6
My system uses frame ground and if you are using a battery then you do not need a cap. The battery will also prevent to high a overvoltage.
 
#7
That is the outlier case. you can't use a full wave rectifier. I built this unit using two inline diodes for each leg then connecting them together. I then. used a cap to smooth the DC. I used it with led bulbs that have no issue with it being unregulated but some led bulbs can't take to high a voltage.
I bought a rectifier on your recommendation. Can I not use it?

I started this thread because I heard there can be problems with AC “noise” when using the frame ground therefore the accessories need to be grounded to battery instead of frame. Other rectifiers seem to have a similar wiring scheme
 
#8
You can't use a full wave rectifier on the tec's with the two independent lighting coils because they are not 180 degrees out of phase with each other and also cause one end of each coil is grounded. Ill get you the correct diode to use and they are very cheap. Here is a pic of the battery I use now. I run it to led lights and it lasts quite a long time before needing recharging. I get them off ebay battery and charger around 20 bucks.
 

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#9
You can't use a full wave rectifier on the tec's with the two independent lighting coils because they are not 180 degrees out of phase with each other and also cause one end of each coil is grounded. Ill get you the correct diode to use and they are very cheap. Here is a pic of the battery I use now. I run it to led lights and it lasts quite a long time before needing recharging. I get them off ebay battery and charger around 20 bucks.
Thanks for the info!
I plan on using all incandescent bulbs. I might just scrap this whole idea and put this lighting coil on a different bike.
Would a half-wave rectifier work? Do they even make such a thing?
 
#10
Yes that is what the individual diodes do half wave. Here is a wiring diagram showing the two diodes in a circuit like yours. Second picture is the original minibike wiring for a 3 amp system. If your LED bulbs actually draw 40 watts that's more than the 3 amp system can provide. It tops out around 35 watts.
 

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