Put any notes, research, thoughts, opinions, presentations, anything about battery modules here!

MS14 Battery Module Design Principles [1].

All modules must be identical
- 3 voltage taps per module
As safe as possible
- All bolts should be electrically isolated //TODO: Find out how to do this
Low budget, fast, safe manufacturing
- Most manufacturing should be done on campus, quickly (so no mass soldering)
Low power cooling [7]
- MSXIV selected Forced Air Cooling over Liquid Cooling, Phase Change Interstitial Material, and Conductive cooling to catamaran.
- MSXIV had multiple fans in parallel to cover the whole width of the battery box.
Normal operation and thermal runaway safety
- //TODO: Find out MS14’s solution
Swappable
Elegant [1]
Easy to assemble [2]
Easy to test [2]
Minimal metal tools required for assembly (for safety) [2]
Minimal loose bolts when removing modules (again, presumably for safety so no loose bolts get lost and end up shorting on anything) [2].

Mechanical Design

Anatomy of a Battery Module – All information so far taken from reading revision logs of MSXIV, may not be up to date yet

Busbars:

Main current-carrying conductors in the battery pack. Used to connect the cells together. Laser cut from EMS Sigma 60, which is nickel and stainless steel clad copper. 60% copper. Nickel and stainless steel enables spot-welding due to relatively higher resistance and lower melting point [3]. For easy, quick and repeatable spot welds, nickel strips were spot welded to the bottoms of the busbars, since the EMS Sigma 60 required too much energy to weld [5].

Gusset Plates:

Used to provide structural support to the vertical mounting points of busbars. See figure below [3]. Mounted using embedded captive nuts and isolated bolts, isolated using insulating washers(now acting as the isolation covers(rev 2)) [4].

Extra clearance was added for the screws that are covered by the gusset plates to ensure that the gusset plates would be able to sit flat against the surface.[6]

Gusset plate highlighted in orange, taken from [3].

Insulation Covers:

Covers used to insulate screws on busbar connections on revision 0 of battery modules [3]. See Gusset Plates.

Cell Holders:

Non-conductive parts used to aid in mounting and busbar connections. Battery cells were accommodated via the use of circular holes in the cell holders. Cell holders also included other mounting features for gusset plates, isolation plates, etc. [3].

Aluminum standoffs(completely isolated from busbars & electrical parts) were added at 4 points central to the module to provide a secondary mechanism to keep the modules together (other than friction). These aluminum standoffs will also be covered with heat shrink to further reduce chances of shorting with damaged modules.[4]

Isolation Plates:

A plate covering the entire horizontal surface of busbars on top of modules to isolate busbars [3]. This is made up of 2 layers: fish paper (electrical grade vulcanized fiber with adhesive backing) [4], and some sort of rigid material used in rev 2+. The fish paper is applied directly to the busbars immediately after spot welding to avoid potential short circuits when manufacturing [4]. Better materials, e.g. Formex were proposed, however, it is noted that these materials may be difficult to find or costly to obtain. The final module used potting compound instead of fish paper to fully encapsulate the spot welds [7], which protects them from damage. See Potting Batteries .

Balance Taps:

Points where the balance wires connect to busbars. The balance wires are used to measure the voltage of every cell in the pack [3]. There should be more information on balancing batteries in the BMS info.

Alignment Pins

Pins used to align the isolation plates and gussets on top of the module.

Pack Layout:

Terminals:

Both positive and negative terminals were at the rear of the pack which allows for easier mounting of HV components and eliminates unnecessary long wiring runs [3].

Joint resistance calculations:

Electrical Contact Resistance for Module to Module Series Connections

-want to minimize unnecessary heat produced

Module Mounting:

The modules will still be mounted with discs glued to the bottom of the enclosure at the corners of the modules. [4]
They should also be the mounting points for cable management brackets in the outer rows[4]
Poron (polyurethane) added to bottom of modules to provide cushioning and vibration dampening[4]

Thermistors:

Thermistors placed directly on busbars as the heat from busbars will heat the thermistors faster there [8]
ASC recommends 1 thermistor per 12.5 cells [8]

Useful Terms:

Contact Resistance: Resistance added because of the interface between two surfaces. Useful to know because this occurs in the contact between anything that touches the busbars (Better check on that). It’s essential to minimize this to minimize power loss [3].

Module Research - MSXV