Jump starting and the modern car..

[The Gaijin]

Wasted half the day (day off) yesterday helping a friend change starter and firewall mounted solenoid in a '98 F-150. The problem turns out to be a corroded cable down to the starter. (Why can't these things breakdown in an honest and straitforward way like a Toyota??)

Anyway - in the whole process we jumped the Ford with my '94 Olds a couple of times. (Thinking the battery was dead.)

Later, I noticed the Olds was not turning over like it should..

Could I have shorted my battery or overheated it or done any other damage? I get no warning lights on the Olds (I think the alternator is fine).

Thanks.