(I know I posted this in another section: didnt know which one would be appropriate)
My freind used his mustang gt 2011 to jump start my friends 06 (approx.) GMC Yukon

Everything went fine at first as we were able to start the yukon

But now my freind (mustang) says his battery is messed up, he says the volts are dropping?? and that it needs to be replaced.

Is this possible, we did need to leave the cars connected about 20min before the yukon started.

Thanks

 

I'd say have him get his Alternator checked, if its not the Alternator, check the battery or replace it...Also might want to examine his battery terminal connectors for corrosion..