Hart 20V batteries (the white and black series sold primarily at Walmart) are part of the TTI family. They share a very similar platform with Ryobi 18V One+ tools, though the physical battery stalks are different.
Unlike some tool ecosystems where the low-voltage cutoff protocol lives entirely inside the battery, Hart batteries rely heavily on the to stop drawing power when the cells drop below 15V. Hart 20v Battery Pinout Diagram
Great for casual DIYers and household maintenance, but power users should stick to the 4.0Ah batteries to avoid frequent downtime. Hart 20V batteries (the white and black series