Reversing Polarity in Battery Puzzle

I purchased a barn find parts 82' Urban Express. The wiring was hanging out of where the battery mount was supposed to be. Initially, I just soldered the green wires together and and bypassed the black/red wires that run to the battery plug since neither was still attached.

I should point out this is my first build and I'm not a mechanic.

I've purchased two batteries and just cut the plug that comes with it and put bullets on to match the rest of the bike.

The bike now runs great but my blinkers and tail lights keep blowing out without battery. This is because the battery regulates the power as it's sending up to 35 volts to lights when throttle is engaged.

When I hook up the battery however it reverses polarity. I've tried splicing a ground near the battery to the engine but this did nothing to solve the issue. Maybe I grounded it at the wrong spot in the circuit? could this cause the reverse polarity?

I'm about to just pull the harness and look to see if maybe I hooked something up weird in my first few days of learning the bike but I can't imagine I would have soldered a red wire to a green one. But going to just completely map each wire according the the wiring map. It's the only idea I have left.

Has anyone ever heard of such an issue other than simply hooking the battery up opposite? (That's not what I did :) )

But something weird is definitely happening. Any random ideas of how I'm feeding power to battery in opposite poles? Or any spot in the wiring that could backfeed to the negative?

Re: Reversing Polarity in Battery Puzzle

There has to be a rectifier in the charging circuit. Find that first...

Re: Reversing Polarity in Battery Puzzle

There is. It's been tested and replaced. Still no dice.

Re: Reversing Polarity in Battery Puzzle

Michael Branscombe /

if the polarity is reversed, can you just swap the connections at the battery terminals? aside from a quick fix shot in the dark like that, you need a wiring diagram and to just trace wires until you figure it out.

Re: Reversing Polarity in Battery Puzzle

Wiring diagrams and multimeters are gold... (edited)

Re: Reversing Polarity in Battery Puzzle

Dirty30 Dillon /

Yeah, batteries can't reverse DC polarity. They always functions with + and - as indicated.

If you are installing the battery and the voltage at your bulbs is reverse, it's because the battery is installed incorrectly. Simply flip the terminals.

Re: Reversing Polarity in Battery Puzzle

> Dirty30 Dillon Wrote:

> -------------------------------------------------------

> Yeah, batteries can't reverse DC polarity. They always functions with +

> and - as indicated.

Actually they can be. And I know someone else that did it by accident.

https://www.batterystuff.com/blog/battery-myth-can-a-battery-reverse-polarity.html#:~:text=Actually%2C%20yes%2C%20but%20not%20without,only%20a%20couple%20of%20ways.&text=If%20that%20was%20to%20happen,has%20been%20charged%2C%20but%20backwards.

> If you are installing the battery and the voltage at your bulbs is

> reverse, it's because the battery is installed incorrectly. Simply flip

> the terminals.

Re: Reversing Polarity in Battery Puzzle

Dirty30 Dillon /

In the case that you have reverse polarity, it is user error, not just a matter of installation. So if you mischarge a completely dead battery, it will function as reverse polarity. It cannot otherwise, just reverse it's polarity due to installation in a circuit.

My question is what type of battery are you using and did you properly charge it?

Re: Reversing Polarity in Battery Puzzle

Tweaker trash /

“The bike now runs great but my blinkers and tail lights keep blowing out without battery”

Yea because that system is made to charge a battery.

Are you trying to run the lights with no battery?

Reverse polarity? Black Is neutral -, red is postive + . A neutral wire goes to frame and neutralize the entire frame. All your lights have a wire that “grounds“ to The Frame to neutralize. Keep the “ground“ wire lightS noRmal & ditch the black battery wire to frame and ditch the rectifier. + wire from magneto to 12v voltage regulator and run the + 12v wire to all your lights

Easy thing to do is take a light bulb and test the wires, & flip if needed

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