Power Tool Battery Technology Explained: Cells, Electronics & Cooling (2026 Guide)

The biggest improvement in cordless tools over the last three years isn’t a new motor or a better gearbox. It’s what’s inside the battery pack.

Every year, tool companies pour millions into marketing new drill models and flashy impact drivers. But the real performance gains — the ones that let a compact tool outperform last year’s full-size flagship — come from battery cell technology. A 2026 cordless circular saw with tabless cells runs cooler, cuts longer, and charges faster than the same saw with standard cells, even though the tool itself is identical.

This guide breaks down what’s actually happening inside modern power tool batteries: the cell types, the electronics that manage them, and the cooling systems that keep them alive. Whether you’re choosing between battery platforms or trying to figure out if those expensive new “FORGE” or “POWERPACK” batteries are worth upgrading to, this is the foundation you need.

Cell Types — The Foundation of Every Battery Pack

Every power tool battery is built from individual lithium-ion cells wired together. The type and size of those cells determines everything: how much energy the pack holds, how fast it can deliver power, how much heat it generates, and how long it lasts before wearing out. Here’s what you’ll find inside modern packs.

18650 — The Original Standard

The 18650 cell (18mm diameter, 65mm long — about the size of your index finger) is the original lithium-ion standard that launched the cordless revolution. These cells typically deliver 2.0-3.5Ah per cell and remain in production today, primarily in budget and legacy battery packs.

You’ll find 18650 cells in Ryobi ONE+ standard batteries, older Makita LXT packs, and most budget-tier cordless tools from brands like Craftsman V20. They’re mature technology — cheap, proven, and widely available. But they’re being phased out of premium lines because physics limits how much energy you can stuff into that diameter.

21700 — The Current Mainstream

The 21700 cell (21mm x 70mm) is the current standard for serious cordless tools. That modest size increase over the 18650 — just 3mm wider and 5mm longer — delivers 30-50% more energy per cell. Most 21700 cells run 4.0-5.0Ah, and they handle higher discharge rates with less voltage sag.

Every major brand’s current lineup is built around 21700 cells: Milwaukee HIGH OUTPUT, DeWalt 20V MAX (5Ah and above), Bosch CORE18V, Makita 40V XGT, and Ryobi ONE+ HP. When you see “HP” or “HIGH OUTPUT” or “CORE” in a battery name, you’re almost certainly getting 21700 cells. This is the baseline for modern cordless performance.

Tabless Cells — The 2025-2026 Revolution

This is the big one. Tabless 21700 cells use the same form factor as standard 21700 cells, but the internal construction is fundamentally different. Instead of welded tabs connecting the electrode foils to the terminals (creating a bottleneck for electron flow), tabless cells use continuous foil collectors that contact the terminals along their entire length.

The result: roughly 50% lower internal resistance. That’s not a marketing number — it’s a physics change that affects everything. Lower resistance means less heat generated during high-current discharge, faster charging capability, longer cycle life, and more sustained power delivery under heavy loads. When you run a 7-1/4″ circular saw through wet lumber, a tabless battery maintains voltage where a standard cell would sag.

Every major brand now has a tabless battery line:

• Milwaukee FORGE — XC8.0 and HD12.0 (launched 2024), using tabless cylindrical cells
• DeWalt XR POWERPACK — launched June 2024, tabless 21700 cells
• Bosch EXPERT — launched January 2026 at World of Concrete, the newest entrant
• Makita BL4040F — XGT platform only, available since 2025
• Ryobi HP Edge — launched 2024, bringing tabless to the value segment

The tabless revolution is the single biggest reason to consider upgrading your batteries in 2026, especially if you regularly use high-drain tools like grinders, circular saws, or impact wrenches.

Pouch Cells — Flat-Pack Power

Pouch cells take a completely different approach. Instead of cylindrical cans, they use flat, rectangular packages that look like smartphone batteries. This eliminates the dead space between cylindrical cells and pushes energy density even higher, while reducing weight.

The trade-off: pouch cells need structural support from the battery housing itself (cylindrical cells are self-supporting), which adds engineering complexity and cost. You’ll find pouch cells in:

• DeWalt XR POWERSTACK (formerly just “POWERSTACK” — rebranded, not discontinued) — the original pouch-cell tool battery
• Milwaukee FORGE XC6.0 — uses pouch cells for a compact form factor (while the XC8.0 and HD12.0 use tabless cylindrical)

Pouch cells shine in compact battery packs where space and weight are at a premium. They’re more expensive to manufacture, so you’ll primarily see them in premium and compact lines rather than high-capacity packs.

Battery Management Systems (BMS) — The Brains

Raw cells are dangerous. Overcharge a lithium-ion cell and it can vent, catch fire, or explode. Over-discharge it and the cell is permanently damaged. Draw too much current and the cell overheats. The Battery Management System (BMS) is the circuit board inside every battery pack that prevents all of this — and in modern systems, it does a lot more.

A basic BMS handles four essential functions:

• Overcharge protection — cuts charging current when cells reach full voltage (typically 4.2V per cell)
• Over-discharge protection — shuts off the pack before cells drop below safe voltage (typically 2.5-3.0V per cell)
• Thermal cutoff — monitors temperature sensors and shuts down if cells get too hot
• Cell balancing — ensures all cells in the pack charge and discharge evenly (critical for pack longevity)

But in 2026, the premium brands have moved well beyond basic protection into full system intelligence.

Tool-Side vs Battery-Side Intelligence

There’s a fundamental architecture decision in how the tool system manages power: does the battery tell the tool what to do, or does the tool manage the battery? The answer varies by brand and has real implications for performance and compatibility.

Battery-side intelligence puts the smarts in the pack. The battery monitors its own state and restricts output when needed. This means any tool on the platform gets the same protection, even older models. DeWalt primarily uses this approach.

Tool-side intelligence puts the smarts in the tool. The tool monitors the battery and adjusts its demands accordingly. This enables tool-specific optimization but means older tools can’t take advantage of newer battery capabilities. Craftsman V20, which relies on basic battery protection plus newer tool-side circuits, falls into this camp.

Full-system intelligence — where the tool, battery, and charger all communicate — is the current state of the art. Milwaukee’s REDLINK PLUS is the most sophisticated example: the battery sends temperature and current data to the tool, the tool adjusts its output accordingly, and the charger optimizes its charging profile based on the battery’s state. It’s a three-way handshake that maximizes both performance and longevity.

Communication Protocols — How Tools and Batteries Talk

When you snap a battery onto a tool, there’s more happening than just electrical contact. Modern battery packs have data pins alongside the power terminals, and the signals they carry determine what the system can do.

Brand	System Name	Communication	Intelligence Level	Key Feature
Milwaukee	REDLINK PLUS	Tool + Battery + Charger (triangle)	Full system	Real-time load optimization
DeWalt	Battery-side BMS	Battery + Tool (bidirectional)	Battery-primary	Runtime estimation (POWERSTACK)
Makita	Star Protection	UART at 9600 bps (XGT)	Tool + Battery	Real-time V/I/temp monitoring
Bosch	CoolPack 2.0	Cell monitoring (EXPERT)	Battery-primary	Thermal management integration
Ryobi	IntelliCell	Extra contacts on HP batteries	Tiered (HP only)	HP tools unlock more performance
Craftsman	Basic BMS	Minimal (voltage only)	Basic protection	Tool-side protection in newer models

*Communication complexity roughly correlates with cost. Milwaukee’s full-triangle system adds cost but delivers the most sophisticated power management.

Thermal Management — Why Your Batteries Die

Heat kills batteries. Not eventually — actively, every time you use them. Every degree of elevated temperature during charging and discharging accelerates chemical degradation inside the cells. A battery that consistently runs 10 degrees Celsius hotter will lose capacity measurably faster than one that stays cool.

This is why thermal management isn’t a nice-to-have feature — it’s the single biggest factor in how long your battery pack will last. And it’s why the shift to tabless cells is such a big deal: they generate dramatically less heat in the first place.

Passive Cooling — Housing Design and Materials

Every battery pack uses some form of passive cooling. The basics: ventilation slots in the housing, strategic spacing between cells to allow airflow, and housing materials that conduct heat away from the cells to the exterior surface.

Bosch’s CoolPack 2.0 is the most aggressive passive approach. The housing uses a thermally conductive material that Bosch claims disperses heat 7x faster than standard plastic housings. It’s not active cooling, but it dramatically reduces the temperature differential between inner and outer cells during high-drain use.

Ryobi’s Cool-Core Pro technology in their HP Edge line uses laser-welded cell straps and internal heat sinks to pull heat away from cell cores. DeWalt uses a ventilated housing design with strategic cell spacing engineered for convective airflow.

Active Cooling — Charger-Based Systems

Milwaukee’s COOL-CYCLE technology in their rapid chargers takes a different approach: rather than just cooling during use, they actively cool the battery during charging. A fan circulates air through the pack while it charges, reducing cell temperatures and enabling faster charge rates without accelerated degradation.

Makita’s rapid chargers (like the DC18RD and DC40RA) also use fan cooling. The charger monitors battery temperature in real-time and adjusts charge current to keep cells within optimal temperature windows. Makita’s XGT chargers can communicate cell-level temperature data thanks to Star Protection’s UART protocol.

Tabless Advantage — 50% Less Heat at the Source

This is where tabless cells change the game completely. In a standard cell, current flows through small welded tabs — thin metal strips that connect the electrode foils to the terminals. Under high current, these tabs become bottlenecks. Electrons crowd through limited connection points, generating resistive heating.

Tabless cells eliminate this bottleneck. The electrode foils connect to the terminals along their entire width, distributing current evenly. The result is roughly 50% lower internal resistance, which translates directly to less heat generation during discharge.

Less heat means less thermal degradation per charge cycle. In practical terms, a tabless battery pack can sustain high-current output for longer before thermal cutoff kicks in, charges faster without overheating, and maintains its rated capacity over more charge cycles. Milwaukee claims their FORGE packs deliver up to 2x more work per charge on high-drain tools compared to standard HIGH OUTPUT packs — and the physics of reduced internal resistance supports that claim.

Pack Construction and Durability

Cells and electronics are only half the story. The physical construction of the battery pack determines how well it survives life on a job site.

Cell Configuration

Power tool batteries wire cells in series and parallel to achieve their target voltage and capacity. A typical 20V (nominal 18V) battery uses 5 cells in series. To increase capacity, manufacturers add parallel groups — a 5Ah pack might use 5S2P (5 series, 2 parallel = 10 cells), while a 12Ah pack could run 5S4P (20 cells).

The series count determines the pack’s voltage. The parallel count determines capacity and maximum current delivery. This is why high-capacity packs can also deliver more power — more parallel cells share the current load.

Housing and Protection

Premium battery packs use glass-filled nylon housings for rigidity and impact resistance. Overmolded rubber corners absorb drops. The housing design also contributes to thermal management — internal ribbing channels airflow, and the material itself may be thermally conductive (as in Bosch CoolPack).

Look for these durability indicators:

• IP ratings — IP56 is common on premium packs (dust-tight, splash-resistant). The Makita XGT line and Milwaukee M18 FORGE packs are rated for job-site conditions.
• Drop ratings — some manufacturers spec drop heights (typically 1-2 meters onto concrete)
• Terminal protection — recessed terminals and dust covers prevent short circuits and contamination

Fuel Gauge Accuracy

The LED fuel gauge on your battery pack ranges from basic (4 LEDs showing approximate charge level) to advanced. DeWalt’s POWERSTACK batteries include an integrated fuel gauge with remaining runtime estimation that accounts for tool type and current draw. Most other brands use simpler voltage-based gauges that can be misleading under load — a battery might show 50% at rest but drop to 25% the moment you pull the trigger on a grinder.

What This Means for You — Buying Guide

All this technology talk is meaningless unless it helps you make better purchasing decisions. Here’s the practical takeaway.

When Tabless Matters Most

Tabless batteries deliver the biggest advantage on high-drain tools — the ones that pull maximum current for extended periods. If you regularly use any of these, tabless is worth the premium:

• Circular saws and miter saws
• Angle grinders
• Impact wrenches (1/2″ and larger)
• Reciprocating saws in demolition work
• Rotary hammers

These tools stress batteries the hardest. Tabless cells maintain voltage under heavy load, generate less heat, and let you work longer before either thermal cutoff or capacity depletion stops you.

When Standard 21700 Is Fine

For lower-drain tools, standard 21700 batteries are perfectly adequate and save money:

• Drill/drivers
• Impact drivers (1/4″ hex)
• LED work lights
• Fans and radios
• Oscillating multi-tools

These tools don’t draw enough current to generate problematic heat in standard cells. You’ll see minimal real-world difference between a $90 standard pack and a $180 tabless pack when driving screws.

Platform Lock-In Considerations

The most expensive battery is the first one — because it commits you to a platform. Your batteries almost certainly cost more than any individual tool you own. Before choosing a platform based on battery technology alone, consider:

• Tool ecosystem breadth — Milwaukee M18 has 250+ tools, DeWalt 20V MAX has 300+. More tools = more value from each battery.
• Backward compatibility — most platforms’ new batteries work in older tools (you get protection benefits, though not always performance gains)
• Entry cost — Ryobi ONE+ HP brings tabless tech (HP Edge) to a platform with $20-30 bare tools

Recommended Batteries by Technology

Here are our top picks across different technology tiers and platforms, current as of February 2026.

Pick	Battery	Technology	Capacity	Why We Picked It	Buy
Best Tabless (Pro)	Milwaukee FORGE XC8.0 (48-11-1880)	Tabless 21700	8.0Ah	Best BMS + tabless combo, REDLINK PLUS	View Deal
Best High-Capacity	Milwaukee FORGE HD12.0 (48-11-1812)	Tabless 21700	12.0Ah	Maximum runtime for demanding tools	View Deal
Best Compact	DeWalt POWERSTACK (DCBP034)	Pouch cells	1.7Ah	Lightest pack, 50% smaller form factor	View Deal
Best Value High-Cap	DeWalt 20V MAX 10Ah (DCB210)	21700	10.0Ah	Massive capacity at competitive price	View Deal
Best New Tech	Bosch CORE18V 12.0Ah (GBA18V120)	Tabless 21700 (EXPERT)	12.0Ah	Newest tabless + CoolPack 2.0 thermal	View Deal
Best 40V	Makita BL4040 (40V XGT 4.0Ah)	21700	4.0Ah	Star Protection BMS, XGT ecosystem	View Deal
Best Budget	Ryobi ONE+ HP 4.0Ah (PBP2005)	21700	4.0Ah	IntelliCell in the most affordable ecosystem	View Deal

*Prices fluctuate. Check retailer links for current pricing. Milwaukee and Ryobi are Home Depot exclusives — you won’t find genuine first-party listings on Amazon.

Full Technology Comparison by Brand

Brand	Platform	Cell Type	Tabless Line	Max Capacity	BMS System
Milwaukee	M18	21700	FORGE (2024)	12.0Ah (HD12.0)	REDLINK PLUS
DeWalt	20V MAX	21700 + Pouch	XR POWERPACK (2024)	15.0Ah (FLEXVOLT)	Battery-side
Bosch	CORE18V	21700	EXPERT (Jan 2026)	12.0Ah (EXPERT)	CoolPack 2.0
Makita	40V XGT	21700	BL4040F (2025)	8.0Ah (XGT)	Star Protection
Ryobi	ONE+ HP	21700	HP Edge (2024)	9.0Ah	IntelliCell
Craftsman	V20	18650 / 21700	None yet	4.0Ah	Basic

*DeWalt’s 15.0Ah is a FLEXVOLT battery (60V MAX / 20V MAX dual-voltage). Standard 20V MAX tops out at 10Ah.