I am afraid I have bad news for you.  Your car would not be considered long term capital gain property, first because it has not risen in value and has no long-term gain and, second, because it would be considered “ordinary income property” since it has been used in your trade or business and depreciated. 

Ordinarily if you give a charity property that has a fair market value of less than your cost basis, you can deduct only its lower fair market value, not its cost basis.  But when you give ordinary income property used in your business, under section 170(e)(1)(A) of the Tax Code you must recalculate the amount you can deduct.  You must reduce the fair market value of the property by the amount of depreciation that would have been recaptured if you had sold the property at fair market value on the day of the gift.  The amount that can be recaptured is the entire amount of depreciation taken during the life of the property.  This rule normally limits the deduction to the remaining cost basis in the property.

In your case, with a fair market value of $50,000, but a recapture up to $80,000, the amount you can deduct would be $0.  You have already deducted the full fair market value of the car as a business expense.  If you had taken only $40,000 in depreciation, you would have been allowed to claim a $10,000 deduction ($50,000 fair market value reduced by $40,000 depreciation recapture).

You are correct that you can deduct only 20% of your AGI for a gift of personal property to a private foundation, but unfortunately you wouldn’t have to worry about that if you make this gift.