A Swollen Battery Cracked the Back Cover. Here Is How Much Room a Battery Compartment Actually Needs.
When a swollen battery cracks the back cover, most of the time it is not a cell quality problem — the structure simply never gave the battery room to expand. After a few hundred cycles, a lithium cell growing 3% to 8% in thickness is normal, and pouch cells are worse. In the projects we have run out of Dongguan, whenever a back cover came back cracked, the investigation landed in the same place…
A swollen battery can crack the back cover of a device when the battery compartment lacks sufficient room for the battery to expand. Most often, the issue stems from inadequate Z-axis clearance in the design. When a back cover cracks, examine the crack pattern before inspecting the battery. A radial or single crack in the center of the cell area indicates insufficient Z-axis space, while cracks at the corners suggest the compartment wall is too rigid.
An edge crack points to a thin cover wall. To resolve these issues, reserve 5% to 8% of the cell's nominal thickness and ensure there is enough space for the cell to expand. The added clearance should be on the side opposite the visible surface, with the side that holds the cell in place being a structural part, not the back cover.
Proper dimensioning of the battery compartment is crucial, with separate treatment for thickness, width and length, and lead side constraints.
Written by urgent.news from Dev.to's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
