You can find third-party adapters at retailers like Power Tools Adapters that allow you to use Hart tools with other batteries (like DeWalt or Milwaukee) or vice versa.
Understanding the pinout is useful for DIY repairs, building adapters, or troubleshooting chargers.
Inside the battery casing, there are often additional contact points labeled C1, C2, C3, and C4 . These are used for balanced charging
When looking at the front of the battery (the end with the terminals facing you, release latch on top), the pins are arranged as follows:
These pins are used for the "Smart" features.