4 miles? Pshh... EASY!

[MadisonMPG]

There is no need for any other wiring? What kind of charger do I need? ( I can't find the one that it came with )

[Christ]

You could use a single 12V charger, or you could use a 24V charger and wire the batteries in series every time you want to charge them (not a good idea, I think) or you could use 2 12V chargers... Or you could use one 12V charger and wire the batteries in parallel, which will work fine.

Choices....

Of course, this assumes they're 12V batteries, not 6V.

Regardless, if you're charging them overnight, just get a 2-5A 12V charger (if they're 12V) and plug it into the leads that go from the batteries to the relay.

That wiring diagram assumes that the batteries are pre-wired, and the relay/motor are up to the voltage of the pack.

What actually happens in the schema is that you push the button, which draws a few hundred mA to actuate the contacts in the relay. When the relay is connected, the motor gets full voltage, and amp draw is dependent on load. For this reason, there is no soft start, no load start, etc... pedal a little bit, get up to speed, then push the button and keep pedaling, with less effort for the same speed.

So I"m going to assume you have 2x12V batteries, a 12V motor.

Wire the + to the + and the - to the - on the battery posts, giving you 12V total (with higher Ah capacity)

You'll want something along the lines of a starter solenoid from an old Ford or some motorcycles (~$10).

Wire your contacts to the solenoid, and put your + so that the large leads on the solenoid are switching the motor's power supply on and off.

Wire the momentary (thumbswitch) to the solenoid's stator lead (small pin with an S over it), and ground it to the bike's chassis.

Ground the battery pack to the bike's chassis.

Run a + from the solenoid to the motor's + lead.

Run the motor's - lead directly to the battery -.

When you push the momentary, the solenoid should click, and the motor will begin spinning.

Remember, 100W is about 1/8 of a HP. I'm sure it will draw more under higher load, but you don't want to let it load down too much, else it will start to overheat.

This is the simplest way I know of. There is no protection at all in this circuit for the motor or the batteries. Don't drain them too much. Later, if you're froggy, you can get a Voltmeter that reads 14VDC, so you can make sure you never take the pack too low. That motor probably will never draw more than about 8-10A for any length of time without overheating... that's about 100W @ 12VDC.

You can get away with 14G wire, honestly. 10G would be considered overkill for 10A.

[MadisonMPG]

It is a 24 volt motor, I think. (if that changes anything)

If I gear it SUPER steep, would it overheat?

[Christ]

If it's 24V, you wire the batteries in series. Sit them side by side, run a wire from the + on one to the - on the other, then Use your open + and - for the remaining connections. It's the same thing as a 24V battery, except using 2 cells.

You're probably best off gearing it at or close to whatever your top pedaling speed is going to be for the area you want to use it, with a freewheel sprocket on it. Overheating is only going to be a problem if you overload it. Don't try to take off with it, and if you notice that you're really slowing down, and you can't even pedal to keep up to speed, it's time to let off the button. You'll get a feel for it. Later on, you may decide to put the 450 on there, or you may decide that neither is necessary.

Personally, I'd use the 450 for something less utility, more fun.

Keep in mind, that if you're going to be going up the hill with this setup, you'll want to gear it so that it can pull you up the hill, but you can work with it to help out.

[MadisonMPG]

It's a motor from an electric skateboard, it has a pretty good grunt to it.

eXkate Powerboard Motorized Electric Skateboards

The motor is mounted to the rear wheels, I am planning on taking off the rear trucks, and sawing it in half, or just removing the other side that is not the drive wheel. Then using a lathe or something grind down the drive wheel to about 2/3 the diameter it is now. That should lower my top speed and give me plenty of grunt. I need to take it all apart and see how it is set before I do anything.

[Christ]

Originally Posted by MadisonMPG

It's a motor from an electric skateboard, it has a pretty good grunt to it.

eXkate Powerboard Motorized Electric Skateboards

The motor is mounted to the rear wheels, I am planning on taking off the rear trucks, and sawing it in half, or just removing the other side that is not the drive wheel. Then using a lathe or something grind down the drive wheel to about 2/3 the diameter it is now. That should lower my top speed and give me plenty of grunt. I need to take it all apart and see how it is set before I do anything.

Yeah, gear it down ALOT... it's setup to do 9MPH on the skate board, which (due to gearing differences) would be insane on a standard bike sprocket.

[JacobAziza]

3 miles, and 1 hill?
Surely this is a joke.

To avoid getting too sweaty, remove as much of your clothing as is legal, and shift to your lowest gear.
If necessary, touch up slightly at the bathroom sink when you arrive, but chances are the downhill will evaporate any signs that you just rode uphill.

Trust me, this will be way easier than you think it is, without any assist.

Motors - and esp. electric motors, tend to add so much weight that they just about compensate for the fact that they are there in the first place.

[MadisonMPG]

Originally Posted by JacobAziza

3 miles, and 1 hill?
Surely this is a joke.

To avoid getting too sweaty, remove as much of your clothing as is legal, and shift to your lowest gear.
If necessary, touch up slightly at the bathroom sink when you arrive, but chances are the downhill will evaporate any signs that you just rode uphill.

Trust me, this will be way easier than you think it is, without any assist.

Motors - and esp. electric motors, tend to add so much weight that they just about compensate for the fact that they are there in the first place.

Like I have said, I have no cardio. I sweat, A LOT! Even if it's not a hard ride in the first place.

[JacobAziza]

Sorry, didn't read all 8 pages.

But still.
My job involves supporting people who bicycle commute (not the hauling job, I have 2).
People make this mistake all the time.

"I have no cardio"
You (and they) have cause and effect reversed.
You don't bike commute because you have good cardio.
You get good cardio BY bike commuting.

It will be hard (and sweaty) the first few times. Probably a week or two at the most. Then it will get really easy, really fast.

2 Years ago it took me almost 2 hours to skate 11 miles to my job as a bicycle mechanic.
Now I do it in half that time (I do have much better skates now, but still)

[thatguitarguy]

That's what I keep sayin'

Cardio is heart and lungs. If you didn't have it, you'd be dead. Use it or lose it.