I kind of have talked about it already over several threads but i think this deserves its own thread.
Here's a picture of my 2s3p cable. It's for the milwaukee electric v28 battery. Each battery is rated for 28v and 3 ah which, when multiplied by 6, is approximately 500 watt hours. This is enough energy to move me about 20 miles at 20 mph.
The connector blocks are approximatly $8 each. I've wired in a fuse, switch and connector. I use solderless terminals for all my connections.
The milwaukee batteries are a relative bargan compared with dewalts. you can get them on ebay or amazon for $85 each. Chargers are $45 each.
What's nice about this setup is that you don't have to open the batteries. You don't void the warrantee this way. The stock bms is strong enough to have 2 in series. If you go with three, the fet will blow.