hooked up the cables backwards when boosting
 

So i tried to boost my civic with my dad's this morning, and the cables were backwards and I didn't realize that. so the cables on my end were black to neg and red to pos, but on my dad's were black to pos and red to neg.

now the thing is i only started my dad's car and not mine, i let it idle for a couple minutes and realized my mistake and quickly turned off the car and reversed the cables.

my question is will there be any hidden damages to both of the cars? they both started and ran fine (other than my civic's radio had to be reset, I'm assuming it's from the surge to the battery?)

another weird thing is I took my civic to a garage to get the battery tested (because my car couldn't start on 2 occasions now), and they showed me that it's still in good condition and the battery is only 6months old. Now i've had the car for longer than that and I never changed the battery on it, BUT my dad had his battery replaced about 6months ago, so could the backward connection have caused the wacky reading?

thanks

ps. yes there were sparks when I connected the cables backwards, no i didn't think more of it, and yes I'm an idiot for doing this... lol

two questions to help me answer your question. what years are the two cars and what kind of car and do you have a multi/volt meter

my car is 2004 civic coup (battery age unknown)
my dad's car is 2001 nissan sentra gxe (battery was bought about 6months ago)
Don't own a multi/volt meter

the mechanic gave me the readout of my civic battery as follows (which I'm a little puzzled b/c I never replaced the battery in the past 6months)

EXP800:
Good Battery
Voltage: 12.75V
Measured: 490 CCA
Rated: 450 CCA
Temp: 20C
Battery Age: 6mo
Avg Life in Area: 51mo
Test Code: 10N6401D9N4

So if the battery is not at fault, the car not starting may be due to something else. I also just cleaned the connecting cables this afternoon with coke and sand paper. took the car for a long ride and will see tomorrow if the battery stays charged...

when it doesn't start what are you doing to start it. and the smart money is on your battery is shorted but i dont see how the tester would pass a shorted battery.

I noticed when I put the key in the dashboard lights come on really slowly, and the odometer took the longest to fade in.

when i compress the clutch and turn the key, the 1st time there'd be a click and very very faint crank, then nothing. if I turn the key again and maintain the turned position there'll no longer be crank but continual fast clicking sounds.

if all you did to get it started was give it more juice then nothing should be wrong but the battery its possible the tester is giving false info if its dead tommoro get a new battery and make sure its charging their should be a gauge on your dash that shows battery voltage. while the car is running it should be a little higher than the halfway mark. their will also be a little battery shaped light on if it is not charging