if the battery was 12.56 AFTER you charged it AFTER wallmart "tested" it, then no, they do not know how to test a battery... it has to be fully charged to get a good reading from the battery tester. fully charged is 13V float, or 12.75V after surface charge is drained... your battery is bad, or it's STILL not fully charged.
what battery do you have? what jumper cables? the excursion should certainly have the battery power to start your car, unless the battery is SOOO bad it won't let the voltage climb to start level, or the jumper cables you are using are total junk.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!