Washing Powder often leaves a soapy deposit on all the anodes (negative terminals) (and a small amount over all terminals). This can short components etc and has to be removed before safely using it. Depends on whether its riskier leaving possible shorts or pulling it apart to clean it... my trouble is getting it out of the casing without destroying it :(
The battery is usually discharged after being through the wash but dont charge it till its dry and preferably cleaned even if you think its going to be fine)
wish me luck :D