You're getting pairs of groups mostly.
Now that it's split, just touch your probes to each end of one of the cans of the 20 rows.
Most meters are polarity protected, so you will see alternating pos/neg as you go, or you can switch the probes each row also.
Standing it up on end will make it easier, or one end hanging off the bench, since you need to get to the side that's touching the bench.
If they're all at about 3.3v like the first one, that's great, and maybe means the battery is fine, and the problem is in the controller or something.
3.3v is pretty close to low voltage as you want to go, but not damaging the battery low, like say 3.0v or lower might.