Backup Battery Pack Can Be Charged via 18V Solar Panel
The Backup Battery Pack was designed with three lithium cells and uses the MPPT method for charging.
Having a battery backup power source during outages or while camping is a great option to have on hand, and while there are a myriad of rechargeable backup battery systems on the market, building your own is also an option. Self-titled maker Anuradha Gunawardana designed a novel Backup Battery Pack that can be recharged via an 18V solar panel with a maximum charging current of 5A.
The charging module for the backup platform uses the MPPT method for charging the three-cell battery pack, which maximizes the solar power energy draw in all weather conditions. According to Gunawardana, “Batteries were arranged with 3 cell series, and 25 parallel(3s25p). The cells were spot-welded using the Spot welder, which I built during my last project. The 12V output of the battery can be connected to an inverter to convert the DC voltage into mains AC voltage.”
Gunawardana designed his Backup Battery Pack’s 3D-printed enclosure with Fusion360, which allowed his to optimize the component placement using limited space. Because of that limited space, he added a 6mm fan to provide air-cooling and prevent overheating. In total, there are 75 Li-ion cells (divided into 3 banks) in the system, which can provide 230VAC through an inverter.
Gunawardana has provided a detailed walkthrough of the Backup Battery Pack on his project page for those looking to recreate his build, but be advised he hasn’t added links to the parts used for this platform, as they were sourced locally. He also hasn’t provided the Fusion360 files used for the 3D-printed enclosure.
But keep in mind, one wrong wiring of a lithium cell, you've created an explosive fire bomb. DIY at your own risk.