11 October 2011

Converting to full DC

I recently converted my scooter to full DC power. Here are some photos and instructions. First remove the flywheel. The Y shaped tool I made didnt work out for me so I used a hefty bar instead. Worked well enough. Note the position of everything so you can put it back later.

Remove the stator from the engine and pull the wire harness out of the tangled mess. I was following the KTM instructions. They didn't fit exactly what I was seeing on my stator. I have a green ground wire on the LEFT side of the CDI coil. They show it on the RIGHT side with no green wire.
I un-soldered the green wire and associated coil wire, as well as the yellow wire and its center-tap coil wire pair. Then, just as the instructions say, add an extension wire to the ground coil wire. I ended up putting the green ground back on the lug. Ultimately it could probably be removed entirely, but more ground connections wont hurt.
Next I soldered the two coil center tap wires together and put heat shrink on the joint. I reused the solder lug to attach the extension wire to the yellow wire. The lug just makes it easier since it holds it in place and keeps it from shorting to anything.
I didnt add any windings to the poles because mine all seemed uniformly wound, unlike the KTM instructions. Overall their instructions were very helpful, but if I didn't know what I was looking at I would have been lost with my stator being just a little different.

 The big deviation begins here. I am having a hard time convincing myself that I need to spend $50 for a $10 part. I pulled a good sized bridge rectifier from my salvaged junk collection. This device has 4 diodes in it that convert 2 phase (or 1 phase) AC into DC. I cut and spliced this into the wire harness from the coil, so that after the connector it would be all DC. This came back to bit me just a bit later on.
Directly on the output of the rectifier, not attached to the rest of the system I was reading 28VDC. I hooked this 28V directly into the battery and the stock regulator. Now the stock regulator is keeping the entire system voltage stable at about 14VDC, even with two 55W headlights on. I'm a little bit worried about the stock regulator and my rectifier getting hot. Today I checked them after my commute and the regulator was cool, but the rectifier was warm. I might add a heat sink to it.
The part that bit me: I had previously installed a relay to switch everything except the auto choke and starter on and off. This relay coil was driven by a small diode + capacitor circuit so it could take AC directly from the stator. This would behave the same was as stock. Relay off when engine not running, relay on when engine running.
You can see the added yellow-red connector-white addition here. This runs up to the relay to make it turn with AC on when the engine runs. Almost perfect! It turns on with the first crank instead of when idling, but it works and I can adjust that turn on delay later. The other option is to add a switch to turn on/off all the lights.
I did run into another problem. Somehow with all my re-wiring I left the auto-choke connected to battery 12V somewhere. The first night after I did this conversion my battery died. it took a bit of head scratching but disconnecting that auto-choke removed the drain and everything is good again. I just need to re-wire the choke into the relay side of the 12V. Or remove it and put in a manual choke.. which seems like a better option.

Next up: installing 1 of 2 HID projector bulbs! I could only afford 1 at the time ok?! I'll get the other next month.

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