Ebike idear
 

So I picked up one of these for 25 bucks in ptetty good condition. I cleaned the sprockets, chain, adjusted the derailers, and put air in the tires.
http://download.bikeboard.pl/foto5/s...nd_control.jpg

I am thinking about 3 or 4 of these

a charger,

and this

http://ebikes.ca/store/photos/NC26RD.jpg

Or the $280 fleebay or amazon set + the cycle analysis.

What say yee oh electric type gurues.

My goal is to be able to take me (290lbs) about 25 (really it's 10 miles to town but a couple extra is a good idea) miles round trip with a few ups and down (200 feet down then back up on the return trip) I would like to haul my kid in a 2 place trailer. 38 volts and 4.5 amp hours per battery.

Batteries in a wooden or aluminum "box" mounted in the triangle mounted to the water bottle holder studs.

I am seriously considering replacing the front fork and adding a disk brake. I can lock the rear brake easily enough with the straight pull, and I will have regin (the hills are steep enough that braking especially with the kid in the trailer will be necessary).

my one worry if I go with front motor is the fork, and with the rear motor the suspension is getting forces it was not stressed for. Specifically at the upper mount and the smaller bushings just forward of the rear drop outs. Though I can lift the front tire and ride in a wheely by pedel power only so I may be worried for nothing, especialy as I am only going to go with a 25 amp controller and it will be mostly on road getting set of hybrid tires for it too (no off-road with the kid trailer)

I am kind of wondering about chargers for those packs, but I will sort that out when I order the batteries some time this winter so I can assemble before spring.

I figure Ebikes like you are talking about draw around 30-40 watt hours per mile at 25 miles per hour, depending on tires, hills and rider weight.
I would go with something like a 36V 20AH V2.5 LiFePO4 Battery Pack because they come with a charger and a BMS that shuts power off before you damage and destroy the battery pack.

If you are going to use a trailer then I would add more batteries to the trailer and plug them in when the trailer is connected, for that you could use cheaper lead acid batteries and an isolating diode to keep the packs separated.

First, there is a lot of debate over on "endless sphere" as to which battery chemistry is better. You might want to do some reading over there before you decide on a pack. From what I could gather when I was reading, LiPo (hobby king pack) is best power to weight ratio and is best for high power bikes where weight and power is more important than range or longevity. LiPo can thermal runaway and explode if overcharged so charging must be monitored more closely. They are only good for several hundred charge cycles but the price is cheaper than LiFe. LiFe (Ping pack above and similar) are best when power output is less a concern than cycle life and easy maintenance. Eg. a longer range, lower power setup. It is a safer chemistry so requires less monitoring when charging but most packs are only good for 2c-3c max so you need a bigger pack to get high watts and they're more money. On the up side, they should be good for up to 2000 cycles, so cost/cycle is less.
Also, if you are talking of wanting a motor that can propel a possible 500lb load at 15-20mph, I think you need to go rear drive, 48 volts and the most wattage that local laws allow for an ebike. Get a big battery pack too.

Wh x cycles / price is kind of how I am thinking. I have all but ruled out lead acid as the weight may be an issue, and I won't always be pulling a trailer with a kid in it. I was also thinking of at least 36v and 20 amp hours for the pack. I am not to conserned with local laws as in some ways it's kind of like the wild west out here. I have also been thinking of going with a gas engine (my only hang up is the noise). The price difference for equilish performance out of electric buys a lot of gas.

I have been happy with the Ping pack I bought last summer but it hasn't had to see any hard use yet. He has a good reputation. Some of the guys on endless sphere were giving and ebay seller that goes by sun-thing28 some good reviews last summer, but I haven't checked recently. you might look at A123 cells if you wanted to build your own pack. If you can afford it, I'd say go with a 48v/1000w rear drive motor and 48v/20ah pack, but it's your call. Hope you have fun with it.

Mostly doing window shopping now but this spring It will be on.