DeWalt PowerStack pouch battery

The DeWalt professional power tool subsidiary of Stanley Black & Decker has become known for it advances in Lithium-ion (Li-ion) batteries, most notably its FLEXVolt range, which combined 18-volt and 54-volt outputs.

Now the company has developed a new type of battery for power tools, using a configuration known as a "pouch" cell. The company calls this its PowerStack battery, and it is set for release in December 2021.

Types of battery

The PowerStack battery uses a technology first seen in production in 1995, known as a "pouch" battery. The other two most common types of batteries are the cylindrical battery, which is the most common in cordless power tool platforms, and the "prism" battery, which is commonly found in electronic devices, including laptop computers and smartphones.

The cylindrical battery is made through a "jellyroll" process, where an insulating sheet is laid down, followed by a thin layer of anode material, a separator layer is added, and a cathode material makes up the final layer. This sandwich is then rolled up and inserted into a hollow cylinder casing. This was the same process used to make Nickel-Cadmium batteries, but it goes back even further than that. It was actually first used back in 1859 by Gaston Plante when he produced the world's first rechargeable battery.

The prismatic cell directly layers the same types of material in what is usually a rectangular container, often made of welded aluminium. These layers can be wound as in the cylindrical cells, or stacked instead. They enable better use of available space (as stacked cylindrical cells always have gaps), but suffer from less viable thermal management, and typically will have reduced lifespan as compared to cylindrical cells.

The pouch cell does away with any kind of rigid enclosure, relying instead on an aluminium plastic film. The layers are of the same type as the other batteries, but are often folded into place. They provide the best power to weight ratio, and the best size to power ratio as well. These usually deliver both more longevity, and high power output than prismatic batteries.

However, pouch cells are difficult to manufacture reliably. Errors in manufacture can result in cells that swell. According to Tesla, which prefers to use cylindrical cells, there are also problems with thermal efficiency. Cylindrical cells can last longer in high vibration environments, while pouch batteries can be sensitive to environmental factors such as heat.

Finally, there is a cost factor as well. Jelly roll cylindrical batteries are very easy to mass-produce, while pouch cells cost more per unit of power.

The PowerStack

This means that for DeWalt to use the pouch battery technology in power tools, it must have found a source for these batteries that has made considerable technological and manufacturing breakthroughs.

The DeWalt DCBP034 PowerStack 1.7Ah battery uses a stack of five pouch batteries. The company claims the battery will provide 50% more power than the comparable DeWalt 2.0Ah DCB183 battery. Where the DCB183 commonly has a life of 500 cycles, the new DCBP034 has a life of 1000 cycles.

The new battery also has just 75% of the volume of the older compact battery. It measures 104mm long by 64mm wide. (Conflicting dimensions are listed for the older DCB183 battery.) The price of the newer battery seems to be 20% above the price of the older battery - well worth it, if the longevity numbers are accurate.

Online reviews

Perhaps the most interesting review comes from Clint at the Tool Review Zone, where the new battery was attached to the new DeWalt compact impact driver, the Atomic DCF850 and put up against Milwaukee's M18 Red Lithium High Output CP3.0 battery mounted on the Milwaukee Generation III Fuel impact driver. The test consists of driving large lag screws without any pilot hole - not what impact drivers are really designed to do, but a good stress test.

While the Milwaukee driver does end up coming out ahead of the DeWalt, the most interesting result is that when the DeWalt is fitted with the older, 2.0Ah battery, it does not perform nearly as well as when using the new battery.

At Shop Tool Reviews, the PowerStack battery is tested when used to de-torque nuts. Again the new battery outperforms the old battery.

Analysis

On the face of it, this is pretty amazing news for the power tool industry. The one thing we don't know as yet is what the runtime is going to be like, and if there will be additional technical challenges in stacking the pouch cells further in the batteries to deliver more amp-hours. Even if that is not possible, having a 1.7Ah battery that is compact and delivers more power than DeWalt's (admittedly ageing) standard 2.0Ah battery is going to be good news for users of the DeWalt compact Atom 18-volt range.

The only real reservation that HNN does have is that pouch batteries have proven really tricky to manufacture reliably. They have been used in a number of electric vehicles (EVs), and the batteries in some of those have been subject to recall. So, it is quite possible that over their first year of release, we could see some defects develop. That's not really a criticism of DeWalt at all, it is just that we've seen some very good companies experience problems in getting this type of battery right.

But, overall, it is certainly good news, and a potentially important advance in portable power tools.