There are several strategies I have seen. First, I highly recommend that you charge to the "LiIo (Lithium Ion)" setting of 4.10V per cell, and set a Low-Voltage-Cutoff (LVC) at 3.65V per cell. For 12S, that would be
49.2V when full, and
43.8V when the battery cuts off.
You could get a small amount of extra range if you charge to a higher voltage and let the battery run down lower, but...it stresses the battery in exchange for a very small amount of range.
Next, you can do a quick bulk-charge of the entire pack to 49.2V each day, which is simple and easy, but...once in a while it benefits the health of the pack if you do a (slow) balance charge. If you ride every day, you might balance charge on the weekend to keep an eye on things, or even every other weekend.
Since a lot of affordable chargers are made for 6S, some of the 12S bikes build their pack as two 6S strings (two groups of 4P/20-Ah in your case), and they balance charge with one power supply that takes 120VAC and converts it to DC, and it powers two 6S chargers.
There would be a pigtail to series-connect the two 6S strings, which makes them 12S, and then plugs them into the controller or bulk charger. For balance charging you would unplug the two 6S sockets (always put the female socket on the battery side, and the male plug on the controller/charger side.
Here are some connectors I like. If you order them from hobby king, also order heat shrink insulation, and silicone-insulation wire (its cheap). The XT60 uses 4mm bullet connectors, and the XT90 uses 5mm
http://www.hobbyking.com/hobbyking/...0_Connectors_Male_Female_5_pairs_GENUINE.html
http://www.hobbyking.com/hobbyking/store/__24707__Nylon_XT90_Connectors_Male_Female_5_pairs_.html
http://www.hobbyking.com/hobbyking/store/__375__58__Hardware_accessories_-Shrink_Tube.html
http://www.hobbyking.com/hobbyking/...are_accessories_-Silicon_Wire_Mesh_Guard.html
There are better chargers and DC-power supplies than what I use, but here is the cheapest you should buy (Hyperion and iCharger are well-regarded).
http://www.endless-sphere.com/forums/viewtopic.php?f=16&t=23465#p341300
Here's an awesome power supply
http://endless-sphere.com/forums/viewtopic.php?f=31&t=45361
It looks like the Hyperion EOS1420i would only need one power supply + ONE charger for 12S for the bulk charging + balance charging (I don't know, never tried this)
http://www.hyperion-eu.com/public/manuals/1420inet_connection_guide.pdf
http://www.progressiverc.com/icharger-306b.html