Short answer: FlexVolt is a battery that runs at 60V in FlexVolt tools and automatically switches to 20V in your existing 20V Max tools. It's one pack that covers both lines. A standard 20V Max pack only runs 20V tools. If you own both generations of Dewalt gear, that difference decides which pack goes in your bag.
I've had crews ask this mid-job with a dead saw and a truck full of mixed packs, so let's settle it properly.
How FlexVolt Actually Works
FlexVolt packs contain 15 cells arranged in three banks of five. In a FlexVolt tool, the pack delivers those banks in series for 60V. In a 20V Max tool, internal switching reconfigures them to deliver 20V.
That's the whole trick. It's not a gimmick voltage label — the pack genuinely operates at two different voltages depending on what it's plugged into. The switching happens automatically through the tool interface.
The Practical Differences
- Voltage in FlexVolt tools. 60V, which translates to more power and faster cutting in high-draw tools like circular saws, grinders, and miter saws.
- Voltage in 20V Max tools. 20V — a FlexVolt pack behaves like a 20V Max pack. Your drill doesn't get 60V.
- Size and weight. FlexVolt packs are physically larger and heavier than equivalent 20V Max packs, because there are more cells inside.
- Price. FlexVolt costs more per pack, reflecting the extra cells and switching electronics.
- Backward compatibility. FlexVolt works in 20V Max tools (with the right shoe/adapter in some cases). 20V Max packs do not work in FlexVolt tools.
| FlexVolt pack | 20V MAX pack | |
|---|---|---|
| In a FlexVolt tool | Runs at 60V | Will not run the tool |
| In a 20V MAX tool | Runs at 20V | Runs at 20V |
| Inside the case | 15 cells in three banks of five | Fewer cells, lighter build |
| Size and weight | Larger and heavier than an equivalent 20V pack | Smaller and lighter |
| Charger | Needs a FlexVolt-capable charger | Standard 20V MAX charger |
Which Should You Buy
It depends entirely on which tools you run.
- All your tools are 20V Max: buy 20V Max packs. FlexVolt buys you nothing except extra weight and cost.
- You run FlexVolt saws or grinders: you need FlexVolt packs — a 20V Max pack won't power those tools at full performance.
- You run both: FlexVolt is the efficient answer, because one pack family covers everything.
The voltage switch is also worth understanding alongside the broader question of how "20V Max" relates to "18V" — we covered that in our piece on 20V Max versus 18V batteries.
Do You Need FlexVolt?
Be honest about your tool list. FlexVolt's value shows up in high-draw tools — saws, grinders, big miter saws — where 60V delivers cuts that 20V can't match. If your work is drilling, driving, and light cutting, 20V Max packs are the right choice and cost less.
For most replacement-battery buyers, the answer is simpler than they expect: match the pack to the tools you actually own. If everything is 20V Max, a good high-capacity 20V pack is the move. Our Dewalt 20V Max 8.0Ah replacement battery is the kind of pack that makes sense for crews running saws and grinders on 20V tools all day.
Charging Both Types
FlexVolt packs use a FlexVolt-capable charger. Standard 20V Max chargers won't charge a FlexVolt pack correctly. If you run mixed gear, make sure your charger is rated for both — or use separate chargers for each pack family. The same principle applies as with any battery: match the charger to the pack. Our lithium battery safety guide covers the charging side in detail.
Frequently Asked Questions
Is FlexVolt the same as 20V Max?
No, but they overlap. A FlexVolt pack runs at 60V in FlexVolt tools and at 20V in 20V Max tools. A 20V Max pack only runs at 20V and won't power FlexVolt tools.
Can I use a FlexVolt battery in my Dewalt 20V drill?
Yes. The pack's internal switching drops it to 20V for 20V Max tools, so it works like a standard 20V pack in that context — just larger and heavier.
Will a 20V Max battery work in a FlexVolt tool?
No. FlexVolt tools need 60V and a 20V Max pack can't supply it. You need a FlexVolt pack for those tools.
Is FlexVolt worth the extra cost?
Only if you run FlexVolt tools — saws, grinders, or high-draw equipment where 60V matters. If your whole kit is 20V Max, a good 20V pack is cheaper and lighter for the same job.
Do FlexVolt batteries need a special charger?
Yes. They require a FlexVolt-capable charger. Standard 20V Max chargers won't charge them properly. If you run both pack types, use a charger rated for both families.