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SolPak

Open Source Tesla style battery pack for EV, Robotics, and off the grid living

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That Tesla Model 3 teradown was pretty cool, neat how its just LT parts with Tesla logos on them instead of LT, you can guess where this is going ;)

SolPak is a rechargeable portable battery pack that can be charged via solar panels or AC mains voltage. The pack uses 18650 lithium ion cells and will be using the ADI LTC6813HLWE-1#3ZZPBF battery balancer/monitor chip suspected to be used by Tesla in the model 3 pack. SolPak will have modular output modules where different DCDC converters or DCAC converters can be swapped in based on end application use. The pack is intended for portable powering of devices, off the grid solar power, portable solar for camping longterm, and custom EVs. 

The overall system in the pack consists of the following:

- Battery Banks (x2)

- Batter balancer/monitor/charge controller board 

- Overall system control board

- Swappable output converter module interface

The battery banks will consist of 18 18650 lithium ion battery cells, there will be two banks in the first prototype. The battery balancer, monitor, and charge control board will consist of two LTC6813HLWE-1#3ZZPBF for monitoring and balancing each bank, the chips can interface with each other to balance all cells together. The cooling system will be integrated in with each battery bank. Right now I am planing copper tubing attacked to copper plate pressed against and between the cells to cool them as loads of current is drawn. The liquid in the copper pipe will be pumped through a radiator or some passive heat exchanger. In the event of a radiator there will be fans.  I'm still developing a solution for the charge controller portion, be I'll have it ironed out in the week. The overall system control board will be based on a STM32 MCU, it will talk to the battery board and the converter module interface, it will run the main firmware that marries together all the subsystems. The swappable output converter module interface is meant to allow the user to choose the outoput voltage for the end application. Swap in a DCAC inverter for 120VAC power to run your laptop or xbox while camping. Swap in a DCDC converter to power your robot etc. 

All this good stuff is going to be mounted in either a custom case made from carbon fiber sheet cut on a CNC with brush aluminum panels here and there or I'll get some off the shelf flight case and use that. What I really want to do is build a frame out of 2020 aluminum extrusion with carbon fiber panels on the sides and to mount everything to the carbon fiber panels, then plat the outside with bushed aluminum sheet. Have holes cut for the radiator and fans to breath. 

General Specs

- 18650 cells two x18 banks

- LTC6813HLWE-1#3ZZPBF Battery balancer and monitor IC

- STM32 MCU for overall system controller

- Custom carbon fiber and brushed aluminum case

- Sealed battery compartment

- Module DCDC converter options, swap out/in converter for give voltage

- DC/AC inverter option 

- Charge with solar panels or AC mains voltage

  • Battery Bank Design

    Adam Vadala-Roth6 days ago 0 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!

  • Introducing SolPak for the Energy Harvesting Challenge!!

    Adam Vadala-Roth06/09/2018 at 20:37 0 comments

    SolPak is a rechargeable portable battery pack that can be charged via solar panels or AC mains voltage. The pack uses 18650 lithium ion cells and will be using the ADI LTC6813HLWE-1#3ZZPBF battery balancer/monitor chip suspected to be used by Tesla in the model 3 pack. SolPak will have modular output modules where different DCDC converters or DCAC converters can be swapped in based on end application use. The pack is intended for portable powering of devices, off the grid solar power, portable solar for camping longterm, and custom EVs. 

    The overall system in the pack consists of the following:

    - Battery Banks (x2)

    - Batter balancer/monitor/charge controller board 

    - Overall system control board

    - Swappable output converter module interface

    - Cooling system

    The battery banks will consist of 18 18650 lithium ion battery cells, there will be two banks in the first prototype. The battery balancer, monitor, and charge control board will consist of two LTC6813HLWE-1#3ZZPBF for monitoring and balancing each bank, the chips can interface with each other to balance all cells together. The cooling system will be integrated in with each battery bank. Right now I am planing copper tubing attacked to copper plate pressed against and between the cells to cool them as loads of current is drawn. The liquid in the copper pipe will be pumped through a radiator or some passive heat exchanger. In the event of a radiator there will be fans.  I'm still developing a solution for the charge controller portion, be I'll have it ironed out in the week. The overall system control board will be based on a STM32 MCU, it will talk to the battery board and the converter module interface, it will run the main firmware that marries together all the subsystems. The swappable output converter module interface is meant to allow the user to choose the outoput voltage for the end application. Swap in a DCAC inverter for 120VAC power to run your laptop or xbox while camping. Swap in a DCDC converter to power your robot etc. 

    All this good stuff is going to be mounted in either a custom case made from carbon fiber sheet cut on a CNC with brush aluminum panels here and there or I'll get some off the shelf flight case and use that. What I really want to do is build a frame out of 2020 aluminum extrusion with carbon fiber panels on the sides and to mount everything to the carbon fiber panels, then plat the outside with bushed aluminum sheet. Have holes cut for the radiator and fans to breath. 

    So far I have ordered a bunch of 18650 cells and I'll be diving into the length datasheet for the LTC6813HLWE-1#3ZZPBF. Once I understand the balancer chip I can choose components and putt together a PCB to be made. Once I get the battery cells I'll be able to get a good idea for how to design the case. I have aluminum extrusion laying around and carbon fiber sheet has gotten cheap so we'll see what happens. Stay tuned folks! 

    Happy Energy Harvesting Challenge Everyone!!

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