Just remember once you put a charged battery in parallel with a discharged battery they are going to try and equalize. If you can still pull start it that might not worry you too much.

"In time of war, send me all the Alabamians you can get, but in time of peace, for Lord's sake, send them to somebody else." General Edward H. Plummer

"Blessed are those who, in the face of death, think only about the front sight." Jeff Cooper