All the cordless power tools today are using lithium battery packs, replacing the old nicad batteries used in the past.
I have a variety of brands of cordless tools, including at lot of random junk of course, and I’ve been comparing the design of the different brands of lithium battery packs, so I can adapt batteries across different brands of tools.
| Ryobi | Ridgid | Dewalt | Bosch | Black&Decker, Porter-Cable, Stanley Fatmax, Craftsman 20V | Makita | Milwaukee | ||
| Product line | One+ 18v | 18v Lithium | 20V Max XR | 18V Lithium | 20V Lithium | LXT | M18 | |
| Personally inspected | Yes | Yes | Yes | Yes | Yes | No | No | |
| Charge over-voltage protection | Pack | Pack | Charger | Charger | Charger | Charger? | ? | |
| Discharge under-voltage protection | Pack | Pack | Tool | Tool | Tool | Tool? | Tool | |
| Cell balancing | In pack | In pack | In charger | None | In pack | None in older LXT packs; unsure about newer | ? | |
| Physical attachment | Neck | Flat | Flat | Flat | Flat | Flat | Flat | |
| Other notes | Fits all Ryobi 18v tools, including older Nicad line | Fits older 18v Nicad tools | Adapter available to use on older 18v Nicad tools | Brands almost identical but not quite; can be interchanged by trimming plastic notches or tabs | ||||
Nicad batteries are simple. You just need two wires from the pack to power the tool, run the tool until it got too slow or weak, then recharge the battery. But the batteries were heavy, and voltage (and tool speed and power) drops rather quickly as the charge is depleted.
Lithium batteries provide better results in the tools, but need protection circuitry to prevent over-charging (which can start a fire) or over-discharging (which can permanently damage the battery cells).
Battery packs with built-in protection circuits inside the pack are easier to retrofit to tools originally designed for nicads. Ryobi and Ridgid have even kept the same battery connection from their older 18 volt nicad tool line into their newer lithium line of tools. Dewalt changed battery connections, but also supplies an adapter (DCA1820) to use the newer XR lithium packs with the older 18v nicad XRP line of tools. Other brands like Makita, Black&Decker, Porter-Cable provide no backwards compatibility.
Note that all of the brands advertised as 18v, 20v, or 20v Max, all operate at the same voltage and power. All are made up of 5 lithium cells in series that measure about 20v fully charged, then drop quickly to an average of 18v in use. 20v battery packs and product lines do NOT have more power than 18v packs and product lines; it is just marketing spin.