On the 3400c's lithium battery board, the black wire is the neg lead; red is the pos; the two white wires connect to tabs between the 2nd and 3rd and 3rd and 4th (I think) cells - but either way go between +/-, and there's a yellow wire that goes to a positive lead.
On yours, I'd venture - purely as an opinion, that the black wire (left on top of the plastic in your picture, possibly) is the negative lead; the red one on the bottom right is the positive lead, the two whites go to tabs. I am not sure about those two-wire braided black ones on the left or the black and red leads on the right.
However, every battery I have seen - NiMH and lithium - thus far has a klixon thermistor (the black rectangle on two red leads on the 3400c battery), which it looks like yours could be missing, though I can't see behind the plastic or what the black thing is. (If that's the contacts I was going to say the leads might be connectors that are disconnected, but there should be five and I can see that the red and black leads appear separate.)
I realize this isn't what you wanted but I get the impression no documentation exists on this, so you'll need to find a dead battery to break open or someone who's done it. I kept notes on my breakdowns for that reason, but I don't have a 2400c.
(Would the EEPROM reset apply to any old battery board? Because despite getting it to recognize, I have not had success getting my 3400c battery to actually charge (or discharge). The NiMH rebuild was a little more successful.)
