building a own E-moped

Hey! I remember those: http://www.digital-brilliance.com/bikes/puch.htm

We had one for a while and I think we manage to ride it around the back yard with at least three people on it :)

I'm pretty sure a 750W motor would be sufficient. 1HP = 745W. However, electric motors are quoted at their "continuous rating" (they can run at that power output 24/7 and never burn out (aside from needing brush replacement)). You can usually reckon on 3 times the power for a peak power output. So, that 750W motor will likely be capable of a peak output of closer to 3HP. I bet the Puch Maxi had closer to 1.5HP max.

Next up, you'll want to consider the controller that goes with the motor. If you're going to run a 36V system then to get 2250W (which is 3 times 750) you'll need a controller capable of 62.5Amps. Check out kellycontroller.com and you'll see they have such a controller for $159. The folks over at electricmotorsport.com have a 750W hub motor (I think).

Alternatively, you could just buy the equivalent already assembled bike: http://www.revevllc.com/xb350.php (full disclosure - that's my site).

There's LOTS of other ways of approaching this - an e-bike setup rather than my moped/scooter biased approach might be more suitable for the Puch.

Man hearing that bike name was a blast from the way, way, past for me.

Good luck!

Jesse,
There are lots of small motors made now for e-scooters. What is your desired top speed? Very roughly, I would figure something like this for the following continuous motor power rating:

<500 watts: <15 mph
500 watts: 15-20 mph
750 watts: 20-25 mph
1000 watts: 25-28 mph

Maybe some of the small cheap chinese PM motors would work ok. TNC Scooters carries some of the "MY1020" motors: here. Beware of the cheap chinese controllers, some of them may be junk, but I think this one might work ok: click here. The motor I have on my scooter is very similar to the 1000w MY1020. It pulls pretty good on the hills with the controller I have that limits the current to about 20 amps. It is the cheapest good quality controller that is available: Navitas TSP100-36, though this will limit the max power to about 600 watts output of the motor (with inefficiencies factored in), so somewhere around 20 mph top speed. Otherwise, a Kelly controller would probably be a good bet.

A BMC motor might also work ok. Here's a source for them. Also, a lot of people have had good results with the "Powerpack" motor & controller.

I use a YiYun YK40.

I tested mine at a solid 33A (according to Doc Wattson), and it works at 48V. No LVC that way, though.

I can attest that this thing is durable:

I accidentally wired a extra 48V pack backwards to it. I heard a pop, and then my bike didn't work. I took it apart, and I guess a cap had failed, because part of the main power trace on the PCB was blown apart o_O. Nothing else looked damaged, though.

After fixing the blown trace, I tested my bike, and it didn't work. I order a new one, and that doesn't work when it gets here. I find out that it was the THROTTLE that had fried. The controller works fine. I now have an extra working controller. Gonna upgrade it, though }:).

Though I wonder: What could have possibly gone wrong that would blow up part of the circuit and fry the throttle's hall sensor, yet leave the controller undamaged?

Those geared motors are weak. They're only rated to 250W, or 1/3hp. Hmm, well, there's a 1200 watt motor in the MY-xxxx series. Overvolting one could probably give you 2000W. Maybe more if you add some sort of cooling. The controller I posted would only just cut it, though, so you probably would want to look into something bigger.

Something like an Etek-R will give you crazy power (15hp+), but kill battery life. Not to mention the motor and controller together are like $900...

Now my question how do electric engines react on different gear ratio's since acceleration is more important then top speed for me. On a 2stroke engine you can take a different gear ratio to go faster but it will go on cost of acceleration and when you go to far it wont get at speed at all is that the same for electric motor's ?

It is similar. An electric motor will heat up hot and run inefficiently if you gear for too high of a top speed. This is kind of different than for an engine, where engines run more efficiently at lower rpms.

That 3,000 rpm is the motor speed at rated power. But, its going to take a lot more than 1200 watts to travel 48 mph. So if you gear for this, the motor will be torqued down, draw more current, and heat up more in an effort to put out more than 1200 watts, and your top speed will be much slower than 48 mph. How fast depends on the current limit of the controller, and this will heat up the motor hot and likely fry it if the continuous current limit is higher than the rated motor current. The resulting top speed will probably be lower than if it was geared for a lower top speed.

Here's a power vs. speed calculator for bicycles that will give you a good idea:
http://www.kreuzotter.de/english/espeed.htm

If you want good acceleration (and hill climbing) than here's my guideline for rated continuous motor power and top speed gearing:

1200 watts: 28-30 mph
1500 watts: 30-33 mph
2000 watts: 34-36 mph
2500 watts: 37-40 mph

These are for PM motors. Serious wound motors are probably too large to fit on your bike so I won't include any guidelines for them, but they would offer a higher top speed for rated continuous power. So, for your desired top speed, than I think this puts you out of the range of the MY#### motors.

Here are some motors that seem just about right (more powerful than motors I listed, but not as much as an etek/Etek RT/Mars etek):
http://www.robotmarketplace.com/products/MAG-C40-300.html
http://www.robotmarketplace.com/products/NPC-4200.html

You'd need at least this controller to power them: http://www.kellycontroller.com/shop/?mod=product&cat_id=4&product_id=9
But, I'd recommend the larger 300 amp model: http://www.kellycontroller.com/shop/?mod=product&cat_id=4&product_id=10

And they can put out high power at 24v, which will make setting up the rest of your system easier. I recommend you use two separate 12v chargers to charge each battery individually to keep them balanced.

1200 watts: 28-30 mph
1500 watts: 30-33 mph
2000 watts: 34-36 mph
2500 watts: 37-40 mph

These seem a little conservative (not necessarily a bad thing). My XM 2000 has a 2000 W continuous rating and it does 42mph on level ground with a 155lb rider (me).

These seem a little conservative (not necessarily a bad thing). My XM 2000 has a 2000 W continuous rating and it does 42mph on level ground with a 155lb rider (me).

They are depending on how you look at it. How much does your XM slow down on an incline? How is your acceleration? And,
he will probably not have a 2-speeds or a dual winding motor.

You do have a good point though. He could get by with a smaller motor with reduced acceleration and hill climbing. That's mostly a budget consideration, as the chinese scooters try and get the highest top speed for a given motor power. Some important considerations are the rider's weight, any cargo, how flat the area, and how many batteries he plans to pile on. Also the motor cooling, and ride length come into play. For example, you can push an etek like hell for a short few minutes, but then it will heat up and fry. Even the temperature of the area you are riding is a factor. But as you can see, there's no way around higher cost for more performance. And the cost difference is not really that much for doing a conversion, while it would be a lot more for a finished product since all the component costs get multiplied each time the product exchanges hands.

IMO, a conversion takes a time, and that reduces the significance of the cost of components. Just my two cents.