I have two battery fleets in my garage. Ryobi 18V packs run my drill and the impact driver, and my Ryobi 40V packs run the trimmer and the blower. Neither one fits the other’s tools. That split is normal across cordless brands, and it’s a big part of why the battery is the real business for all of them.
DeWalt took a different route back in 2016 with FlexVolt, a pack that delivers 20V in a drill and 60V in a table saw without you touching a thing. Slide it onto a different tool, and it reconfigures itself. The idea still looks clever a decade later, though the label hides some math that catches buyers off guard, and the design carries a few costs DeWalt doesn’t advertise.
One pack holds two batteries’ worth of wiring
Fifteen cells, arranged in three groups
A standard DeWalt 20V MAX pack strings five lithium-ion cells in a row to reach 20V at full charge. A FlexVolt pack holds 15 cells, split into three of those five-cell strings. How the strings connect to each other decides the voltage.
Wire the three strings side by side, in parallel, and the pack still puts out 20V, but with three times the capacity of a single string. Chain them end to end, in series, and the voltage triples to 60V while capacity drops back to that of one string. The cells are identical in both cases. Only the path between them changes.
That’s the whole trick, and it’s good old electrical engineering at its best. What DeWalt added was a way to make the swap happen inside a sealed pack, thousands of times, with no input from the person holding the tool.
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No switch, no app, no setting to forget
Credit: Dewalt.com
Nothing on a FlexVolt pack lets you pick a voltage. DeWalt cut the battery slot on its 60V MAX tools to a different shape than the 20V MAX slot. Push a pack into the 60V version, and that shape nudges the contacts inside over to series. On a 20V tool or a charger, the contacts stay in parallel.
Because the tool’s shape does the choosing, there’s no way to feed 60V into a 20V drill by mistake. That’s a different safety problem than how DeWalt and Ryobi handle battery protection, but it follows the same philosophy of putting the decision in the tool.
DeWalt also sells 120V MAX tools, such as its 12-inch miter saw, which take two FlexVolt packs at once and stack them to reach corded-level voltage. It’s the same packs with a third configuration.
The label math trips people up
A 6Ah pack is also a 2Ah pack
Credit: DeWalt
FlexVolt packs come in 6Ah, 9Ah, 12Ah, and 15Ah sizes. Those numbers describe the pack at 20V only. Move the 6Ah pack to a 60V circular saw and it behaves as a 2Ah battery. The 15Ah monster becomes 5Ah.
The pack didn’t shrink. Multiply volts by amp-hours and you get 120 watt-hours either way, whether that’s 20V at 6Ah or 60V at 2Ah. A 60V saw draws its power with more voltage and fewer amps, so the wiring runs cooler and a hard cut bogs the motor less.
Shoppers who compare amp-hours across voltages often get this wrong. It’s the same trap behind the battery game all three big brands play, where one printed number rarely tells you what the tool receives. Watt-hours is the fair comparison, and DeWalt prints it on the pack in small type.
Where the design costs you
Heavier, pricier, and picky about direction
Credit: DeWalt.com
All those extra cells add weight. Hang a FlexVolt pack off a compact 20V drill and the balance goes straight to the bottom of the grip, which gets old fast when you’re driving screws into a ceiling. Plenty of DeWalt owners end up with slim 20V packs on the drill and FlexVolt on the saws and grinders for exactly that reason.
Compatibility also runs in a single direction. FlexVolt packs power 20V MAX tools, yet ordinary 20V MAX packs won’t run 60V MAX tools at all. Anyone who buys a 60V table saw as a bare tool and expects existing batteries to work is in for a second purchase, and FlexVolt packs sit at the top of DeWalt’s price list.
Then there’s the red plastic cap that ships on every pack. Carriers cap lithium batteries at 100 watt-hours apiece, and the cap keeps the three strings disconnected so each counts on its own. Toss it and the pack becomes harder to mail or fly with.
Ryobi owners like me are still carrying two chargers
FlexVolt solves a problem I live with every weekend. A dead 40V pack in my trimmer gets no help from the six 18V packs on the shelf. Ryobi’s combined charger tidies up the bench, but I’d still own two sets of batteries. With DeWalt, the pack that ran your drill all morning can go on a table saw after lunch. That matters most if saws, grinders, or yard tools are on your list, so count it when you pick a platform. Check watt-hours before amp-hours, buy a couple of small packs for the drill, and don’t throw away that red cap.