However the power required will be high if the alternator is providing it's full output to a battery and lower when it's providing small currents. So the power required to spin depends on the electrical load. Why not see if your car manufacturer has a web page and ask them. General battery and charging safety information may be found in our instruction manual. Answers to a lot of common questions are found there.
Hot weather is hard on batteries.
Park in the shade. I talked to a man who parked his car in the sun on a very hot day in Phoenix, Arizona and found that his battery had exploded. He needed a new hood. His dealer said he wasn't the only one. He put a thermometer on the new hood to see how hot it could get.