Battery Bank Design

A project log for SolPak

Open Source Tesla style battery pack for EV, Robotics, and off the grid living. Modular design for multisize packs

AVR (lordKiCAD)AVR (lordKiCAD) 06/12/2018 at 02:090 Comments

Today I spent some time brainstorming the design of the battery bank in the pack.  As mentioned before I am wiring up two banks of 18 18650 lithium ion cells. I have decided on the wiring configuration as of yet. The two banks will each be monitored by the battery monitoring and balancing board that will have LTC6813HLWE-1#3ZZPBF for each bank. 

Not going to lie most of my inspiration today came from looking at lots of model S battery teardown pictures. I'm taking more inspiration from the model S since theres more info out there and it uses the 18650 cells. I guess in essence I'm combining the battery management of the model 3 with the cell tech of the model S but I'll get back to the main point. The main point being is when you pack a bunch of these lithium ion cells close together in a sealed containter they are going to get hot, they need to be cooled. The Tesla Model S packs are liquid cooled, I will be applying this method of cooling to the solPak as well. I'm not sure how I'm going to exchange the heat from the battery cells into the water yet but I'm working on it. I'm thinking some thermally conductive material that can conform to the batteries somehow, either running fluid through it or coupling it to piping. 

So I have these battery banks, a board, and a liquid cooling system, what I'd like to do is package it all as a sub module, like in the following diagram:

The batteries will wire into the main rails, which I plan to make from copper barstock from mcmaster-carr, and will also be wired to the BMS/balancer board. The liquid cooling heat exchanger blocks will wrap around and sandwich the battery banks. All this will be packaged as a sub module. The idea being that many of these modules can be used to make a very large battery pack. Thats all I got for today!! Next post will be discussing the BMS board, wiring of banks and more details on the electricals, this project is building slowly as I am learning almost everything as I go!