8.89 Volts is pretty good for a 6-cell pack. That's over 1.4 Volts per cell. Your charger is working properly, but you should probably stick with the 1 Amp charge rate. 4 Amps is too hard on the battery pack. For future reference, the rule of thumb is that 1 times the battery's capacity (also referred to as C) is a safe charge rate for ALL packs.

You left out some important information: Motor, gearing and prop. That, and cell count, determines the Amp load that's put on the battery.

An 1100mAh battery, whether NiCD or NiMH, should easily be able to handle a Slow Stick and fly it for 20 minutes. There is something wrong here. You've got to have one of these:
1. Crap battery
2. Severe binding in the gearbox
3. Bad motor
4. Wrong prop for the gear ratio
5. Wrong gear ratio for the prop

Can't tell without more information, though...