A quick look at the failures of these packs that have a tough life mechanically and the DIY abuse mode is to use (discharge) and then store them in a discharged state until required again in 6 months time. Hence cell imbalance and over-discharged pack failure modes are common.
One issue that comes up over and over is that these packs need to be interchangeable between brands. This would significantly reduce waste, and would also make repairing a pack far more practical than replacing it outright.
Pack Formats and Power vs. Voltage
Most cordless power tool packs are still built around 18650 or 21700 cylindrical cells. The numbers describe diameter and length in millimetres, so a 21700 cell is simply a physically larger cylinder than an 18650. Moving to 21700 buys more capacity and current per cell, but because the dimensions differ, a pack built for one format can’t be dropped into a tool housing designed for the other without a new mechanical design. This is why brands often sell an “18650 compact” pack alongside a “21700 high-capacity” pack on the same voltage platform, rather than replacing one with the other outright.
Voltage and power also get conflated in marketing: the “18V vs 20V Max” split isn’t two different battery platforms, it’s the same 5-cell-in-series pack labelled either by nominal voltage (18V, around 3.6V per cell) or by peak no-load voltage (20V, around 4.0V per cell). DeWalt and Black+Decker favour the “Max” figure, while Makita, Bosch and Milwaukee stick to nominal. Real delivered power (W = V × I) depends much more on the pack’s continuous discharge current, set by the per-cell current rating and how many cells sit in parallel, so two packs with an identical voltage label can still differ substantially in how much power they can actually push into a motor.
BMS and Charging Practices Specific to Tools
Power tool BMS design is shaped by current more than energy density. A drill or impact driver pulls short, hard current pulses under load, so tool packs favour cells selected for high continuous and pulse discharge current, often at some cost to the pure energy density prioritised in laptop or phone cells, with the pack’s real current ceiling set by how many of those cells are wired in parallel. That duty cycle (long idle stretches punctuated by hard pulls) is also why balancing matters more here than in most consumer electronics: cells drifting out of balance during storage is exactly what produces the over-discharge and imbalance failures already covered on this page. It’s also why tool chargers tend to run fast (many packs charge in well under two hours) with active temperature monitoring, to avoid pushing already-stressed cells too hard on the way back up.
Right-to-Repair and Interchangeability
Cross-brand interchangeability isn’t purely aspirational: it already exists at real scale, just not industry-wide. The Cordless Alliance System (CAS), built on Metabo’s 18V platform and launched in 2020, lets roughly 50 brands and 500+ tools share one battery, which is a working example that a common interface doesn’t have to stop manufacturers competing on the tool itself. Most of the largest brands (DeWalt, Milwaukee, Makita, Bosch) sit outside any such alliance, but regulatory pressure is building regardless: the EU Batteries Regulation (EU) 2023/1542 will require portable batteries to be readily removable and replaceable by the end user from February 2027, and the separate EU Right to Repair Directive (EU) 2024/1799, in force from July 2026, obliges manufacturers to offer repair, spare parts and repair information. Neither forces cross-brand interchangeability directly, but both push pack design away from the sealed, glued, single-brand-only construction that makes swapping or repairing a pack difficult today.
Legislation and Standards
- Power
- The rated power of corded products is measured according IEC 62841-1. The equivalent power of cordless (battery powered) products indicates the performance in comparison to similar corded products. The equivalent power depends on the capacity, type,state of charge, temperature and health/age of the battery. [1]