Idea for an electric push trailer... let me know what ya think...

[mrspock]

???

Its a cool bike, but it doesn't fit my needs at all. I live in NY, and motorized bikes are illegal... Which is why I need an electric one, which is silent, and I can hide fairly well within a trailer.

Do we think 24v and 24ah is sufficient for a 450watt motor to assist me for about 30 miles, some of which is over hills? If need be I can purchase 2 more batteries so its 24v and 36ah to be sure I would have enough power.

I think you are way over estimating the range you will be able to get. If you use a 24v motor and two 12v 12ah batteries, your total ah (amp hours) will only be 12, not 24. Batteries are wired in series. No matter how many you wire in series, you still only get 12ah. 25 miles is a very long way on most ebikes. If you even carry extra batteries, look at the weight you will be toting around. Pedaling won't be near as easy as you think when pulling that much extra weight, especially up hills. With the distance you say you need to travel, an electric scooter would be better but with most current models, you'd still need to recharge while at your girl friend's. But since your budget is $300, an electric scooter would be out of the question since they run closer to $1000. However, for around your price range, you could buy a Currie Ezip bike ($300-$400 range). They are currently $398 at my local Wal-Mart. They come with one battery pack and you can add another. But 50 miles round trip would still be pushing it. Weighing 300 lbs would be a major strain on the batteries. I've driven this bike for almost 2 years with no problems except the battery contacts wearing out from the constant vibration of the road. I really think your best bet would a small gas scooter, which would carry your weight and be a miser on gas too and you would have no worries about running out of juice. You could get your exercise from a mountain bike on the side.

 

[mrspock]

looks really awesome to me .. you could even add a generator for range extension... perfect

You can't use any type of generator to replace the power you're using while the bike is in motion. This is getting into the perpetual motion scenario. An ebike gets all its power from the batteries and some from pedaling. The bike is using too many amps too quickly to replenish. You could strap a gas generator on the bike but it still could not charge the batteries as fast as you were draining them. Plus, the extra weight of the generator, even if a lightweight one, would just make the batteries drain even faster. And there's a lot of variables that make solar charging a bike very inefficent also. The best comparison is a cordless lawn mower. They typically are 24 volts with two 12v batteries, just like many electric bikes. At least one cordless mower manufacturer offers a solar panel option but they tell you up front that under ideal conditions, it takes 3 sunny days to recharge the batteries and of course, that's with the mower turned off while recharging. 5 days or more for cloudy days. It would take a lot of square footage of solar panels to carry around on the bike and that's just hauling them and not using them. No way you could set them up to use on the bike while running it unless the bike was 10-15 ft long. Would be very awkward on a bike. Just like a gas generator, the solar panels couldn't keep up the charge while the bike is in motion. I'm not referring to the experimental vehicles that run directly off the panels and sit on the ground. I'm referring to a bicycle.
A lot of people bring up the generator or solar thing with ebikes but you need to realize that this would already be being done if it was at all feasible.

 

[bigkat650]

I think you are way over estimating the range you will be able to get. If you use a 24v motor and two 12v 12ah batteries, your total ah (amp hours) will only be 12, not 24. Batteries are wired in series. No matter how many you wire in series, you still only get 12ah. 25 miles is a very long way on most ebikes. If you even carry extra batteries, look at the weight you will be toting around.

Well the original plan was to use 4 batteries total, not 2... wired to create a 24v 24amp load

Honestly I should kill this thread because I have completely rethought the idea, and a simple hub drive is the way to go with LiPo batteries instead of SLA... just debating on geared or non-geared now