Sorry, explain what you did again/post your raw measurements? Those are all over the place, as I’m sure you’re aware. I’m hoping the C2 measurement is 2 cells in series, because otherwise you’re way over voltage on that cell group.
But if one cell group is below 2.0V, as seems to be the case, you probably should scrap the battery. That’s getting into “cell abuse” voltage levels - I don’t like below 2.5V/cell unless I know exactly how and why it was there, and it was very brief.
Probably. Don’t load up batteries asymmetrically like that, it’s not within the design spec for any balancer or anything else.
The “default behavior” (unless you perform the proper incantation, which, if done wrong, will brick the battery) is to behave like a 20 Volt Max pack, so a 3P5S pack. It reconfigures to the 15S pack when the right things are done in a 60V tool.
You currently have each cell group in parallel, so get them close to each other.
You should be able to do that. But I really don’t suggest messing with a lithium pack when one group is below 2.0V. Sorry, the safest thing is to scrap it at that point. I’m aware there’s no shortage of people who’ve done it, and it works, for a while, but “stressed lithium” is a hazard waiting for an inconvenient time to let loose.
And I’m just assuming that 5V measurement is two in series, otherwise if you’ve got an actual cell group that high, and another one sub-2.0V, do not mess with the pack, find a way to discharge it, and scrap it.