This video from the Weber Auto YouTube channel introduces the new 12.8-volt lithium iron phosphate (LFP) low-voltage battery found in the 2026 Tesla Model Y, which is offered alongside the existing 16-volt lithium-ion battery. The presenter, Professor John Kelly, explains the key operational differences between the two, noting the LFP battery runs at 14.4V and 100% state of charge, while the lithium-ion version runs at 15.5V and a 79% state of charge. The core of the video is a practical demonstration of replacing the stock 12.8V LFP battery with the 16V lithium-ion battery. The process requires specific software procedures within Tesla's Service Mode, including using the "Learn New Battery" function followed by a complete software reinstall to ensure the vehicle's power conversion and control systems correctly manage the new battery. A key takeaway is that this compatibility is one-way; the 16V battery can replace the 12.8V, but not vice-versa.
Tesla's New Low-Voltage Battery: A Guide to Swapping and Compatibility
0:00:02 New Battery Introduction: A new 12.8V lithium iron phosphate (LFP) low-voltage battery is now available in some 2026 Tesla Model Y vehicles, co-existing with the 16V lithium-ion battery that has been used since late 2021.
0:01:10 Key Operational Differences: The new 12.8V LFP battery operates at ~14.4 volts and is maintained at a 100% state of charge. In contrast, the older 16V lithium-ion battery runs at ~15.5 volts and is typically kept at a 79% state of charge.
0:01:24 Vehicle System Adaptability: Newer Model Y vehicles can support either battery, but the vehicle's control systems must be properly configured for the installed battery type. The electrical connector is physically compatible with both.
0:03:22 The Battery Swap Experiment: The presenter demonstrates the process of replacing the original 12.8V LFP battery with the 16V lithium-ion battery to show the required steps for the car to accept the change.
0:04:03 Safe Removal Procedure: To replace the battery, the vehicle must first be powered off via the touchscreen. Then, the electrical connector (ECPA clip) is unplugged from the battery, and the high-voltage system is disabled by disconnecting the under-hood cut loop.
0:05:00 Essential Software Configuration: After installing the new battery, the vehicle must be put into Service Mode. The "Learn New Battery" function must be initiated, followed by a "Software Reinstall" for the CAN ECUs to update the battery management system.
0:05:45 System Calibration Time: After the software update, it can take several hours for the vehicle to accurately read and stabilize the new battery's state of charge, eventually settling at the correct level (e.g., 79% for the 16V battery).
0:06:11 One-Way Compatibility: A crucial takeaway is that while a 16V lithium-ion battery can be used to replace a 12.8V LFP battery in a compatible vehicle, the reverse is not possible.