Thinking of kicking off a new project!
While I cannot afford a Tesla PowerWall, I’ve spent some time drawing up a PCB to house 7x 18650 cells in series. Each board has onboard Battery Management:
- Overvoltage Protection (per cell)
- Undervoltage Protection (per cell)
- Balance Charging
- Overcurrent Protection
- Main pack Fuse
Each PCB has pads that allow you to stack them on top of each other with some 25mm Brass spacers, to increase the pack capacity by joining several 7S strings in series (for example stacking 10x PCBs gives you a 7S10P Battery. If you used 2500mAh cells, that would be a 21-29v 25Ah pack!
Costs are looking good, in the region of under $15 per board, keeping in mind it includes the BMS circuitry, that’s pretty cheap!
If you want to order some boards, checkout: https://www.pcbway.com/project/shareproject/18650_PowerWall_with_Onboard_BMS.html
Eagle Files: https://github.com/openhardwarecoza/DiyBMSv418650pack
Currently raising funds, need to order cells, boards and parts (:
If you want to contribute, get in touch https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=45DXEXK9LJSWU