BMS is Battery Management System - it is the circuit board on top of the battery. There are 13 groups of 4 cells in parallel, with 14 connections from the cells to the BMS. In your battery, the cells' attachment to the BMS is sealed with black sealant. You may be able to penetrate the sealant with a pin connected to your voltmeter. You need to test pairs of these connections.
This was easier with the Standard Battery, as the contact points were exposed and clearly labeled.
This was easier with the Standard Battery, as the contact points were exposed and clearly labeled.