If you measured a voltage of 11; than that battery was stone dead. See the chart below.
A battery's voltage should not be measured while on the charger. So, when that second battery read 100%, it was measuring the effect of the charger.
Tell DH to follow the instructions for charging the new battery he is buying. It might take a long time to fully charge depending on its state of charge from the store.
You asked if it could be the ground? Yes, that's the next thing to check after checking the health of your battery. You can remove the ground, clean with a wire brush and re-attach.
Try again with a fully charged good battery. If you still have a problem, then it gets more complicated.
DW, 3 Kids and our Goldens
2012 Shamrock 233S
2008 Toyota Sequoia 5.7L 4WD