16 Cell Layout with a Pathfinder BMS

While I’ve been working on the new user manual, the programmer is making great progress on the firmware.

I’m pretty happy with how the new illustrations are looking. Here’s a preview: The cell connections for a 48v 16 cell LiFePO4 battery:

Figure? Shows the general layout of a 16 cell battery. Note that the most positive terminal (BC16) on the group of cells is connected only to BC16 and the “+Cell” terminal of the BMS. The “B+” terminal connects to the positive side of your electrical system.

The most negative terminal (BC0) on the group of cells is connected to the negative (or ground) side of your electrical system. It is OK to connect this wire to a chassis ground, if applicable.

It is difficult to draw all 16 cells on a single page. See figure? For a zoomed-in view of the balance wire connections. All 17 balance wires (AKA voltage sensing wires) must be connected as shown. See note 1.

Note 1: Which stud to use? Where is BCx?

We usually specify that each balance wire should be attached to the positive terminal of the corresponding cell. 

For example, connect wire BC2 to the positive terminal of Cell 2. 

This is only for consistency in the instructions, because anywhere on the node between 2 cells is the same as far as electricity is concerned. 

For example, wire BC2 can be connected to the positive terminal of cell 2, or to the negative terminal of cell 3, or it can be bolted or soldered to the center of the bus bar connecting these cell terminals. In fact, attaching the wire to the center of the bus bar may be technically superior, but we don’t think it’s worth the extra effort in practice.