ORIGINAL: HangGlide
Mine is on the desk next to me. For model# U090020D12, Output: 9V DC @ 200mH.
So the rate that charger trickle charges is .2 amps per hour or 200mA per hour.
So take the capacity or your battery and divide it by the charger's charging rate.
1600 / 200 = 8
So around 8 hours that charger will charge a 1600mAh battery (of course it may be shorter if the pack has any charge)
I take it that is a NiMH battery, if it is a NiCD be sure to discharge it properly or you'll start screwing up the cells. Trust me I killed a lot of NiCDs in the 80's when I started this hobby. I doubt I'll ever use a NiCD again unless I have too !!! NiMH is good for me untill lithium based batts get cheaper.