Well I finally got my ESC's and am about to go through the cal, but my battery was dead.
Charger doesn't want to bring it up, says Battery Check Low Voltage
Many years ago I was an Aircraft Electrician and spent some time in the battery shop.
This method actually made sense, the charger is not supposed to charge a battery that has fallen below a certain point. So the answer is get the battery back above that cutoff point, at least long enough to get the charger to take over.
As stated above you do have to keep an eye on them, and only push it for a minute or so.
Quickly switching modes and starting the cycle seems to work.
Maybe this will work on my 3s pack I had 2 cells that made it also say low voltage. The 1 cell is at 4.20 the other 2 are the ones making it read low voltage