I decided to get some measurements on my DSD charger, and I'm surprised - it actually shuts off rather than trickles. Voltage rises to 4.23 or 4.24, then charger cuts off, light turns green, voltage slowly dropping to 4.10-4.15ish depending on the cell.
I'm not sure how it senses the cell is present, but it seems to be a very, very high impedance circuit - merely touching the cell to either terminal turns the light green, as does touching one of the contacts - you don't need to actually have the cell in, or touch both contacts. So I don't think it's trickling to sense the cell, either.
LED blinks red/green with no batteries, red while charging, green when charged.
All four sets of contacts are simply wired in parallel (based on them all having the same voltage when any one is used - I haven't taken it apart), which works fine if you put in reasonably-matched batteries, but if you put a completely dead battery in one side and a fully charged one in the other, I can see the maximum charge/discharge rates being exceeded as the good one charges the drained one.
Batteries are a bitch to get out if you put two 18650s in - you need to either pry them out, or flip the charger over and whap it against your hand. Protected cells just barely fit, but do fit. Larger protected cells, like the ultrafire 3000s, won't fit at all.
Overall construction quality feels flimsy at best, and I can't imagine the life expectancy is very good, especially if roughly handled.
The ac adapter whistles. No sign of any agency approvals, but they'd probably just be fakes anyway.
English translations are some of the best I've seen lately... or, at least, best for providing amusement.
Charge time is rather slow, especially with two good 18650s.
Absolutely no differentiation between positive and negative contacts - both are identical. Must look at markings to get polarity correct. Would be very, very easy to get a cell in backwards.
But... it doesn't trickle!
Here's some photos:
--Bushytails