Batteries can discharge hazardous gases or present fire or explosion risks if these are overcharged or charged incorrectly.  For these reasons, batteries should be charged in hoods when possible.
Batteries typically contain highly corrosive electrolytes that users can be exposed to if filling or in events of leakage.  Shipment and disposal of most batteries are regulated.  Follow the requirements.  Please see the SOP document in the link above for additional information.