Guide · Cordless and battery platforms
20V MAX vs 18V batteries
DEWALT says 20V MAX is 20 V without a load and 18 V nominal. Why the label is not more power, and why no voltage number makes a pack fit another brand's tools.
Short answer
"20V MAX" and "18V" describe batteries of about the same nominal voltage. DEWALT's own footnote says its 20V MAX packs reach a maximum initial voltage of 20 volts without a load and have a nominal voltage of 18.[1] The label does not mean more power, and it does not mean a pack fits another brand's tools: Makita and Milwaukee each say their batteries work only within their own platforms.[2][3]
Two ways to write the same voltage
A lithium-ion pack's voltage is not fixed. It is highest when the pack is freshly charged and resting, and it sags under load and as it discharges. Makers can label a pack with either number:
- Maximum initial voltage: the resting voltage of a full pack. DEWALT's "20V MAX" uses this, and says so: maximum initial battery voltage, measured without a workload, is 20 volts.[1]
- Nominal voltage: the typical voltage during use. DEWALT gives its 20V MAX packs a nominal voltage of 18.[1]
Milwaukee lists its M18 packs as 18 V and Makita names its platform 18V LXT.[3][2] The pages we read do not say whether those are nominal or maximum figures, but DEWALT's footnote shows that an "18" and a "20 MAX" can describe the same class of pack.
So a "20V MAX" label does not put a pack in a higher class than an "18V" one. Neither label tells you how much work the tool does; that depends on the motor, the electronics and the pack's capacity.
| Label | What the maker states | Platform rule |
|---|---|---|
| DEWALT 20V MAX | 20 V maximum initial voltage without a load; 18 V nominal[1] | Not covered in our research |
| Milwaukee M18 | 18 V[3] | M18 packs in M18 tools only[3] |
| Makita 18V LXT | 18V in the platform name | LXT packs in LXT tools only[2] |
The label is not a compatibility test
Each maker keeps its platform closed. Milwaukee says its batteries are interchangeable within a system but not across systems.[3] Makita says its batteries are compatible only within each platform, with LXT batteries going in LXT tools.[2] Neither says anything about other brands' packs, because they are not part of the system.
The same applies inside one brand. Milwaukee's M12 (12 V), M18 (18 V) and MX FUEL (72 V) packs each run only their own tools,[3] and Makita separates 12V max CXT, 18V LXT and 40V max XGT.[2] Makita's 40V max XGT is a separate platform from its 18V LXT line, not a stronger version of it.[2]
What this means when you buy a cordless polisher
- Start from the platform you already own, not the number on the label.
- Match the brand and the platform name (M18, 18V LXT, 20V MAX), not the voltage.
- Ignore cross-brand adapters. No maker in our research approves one; see genuine vs aftermarket batteries.
The battery compatibility guide lists what each polisher maker says fits.
Next
Questions
Is 20V MAX more powerful than 18V?
Not by the label. DEWALT says its 20V MAX packs reach 20 volts maximum initial voltage without a load, and that their nominal voltage is 18.[1]
Can I use a 20V MAX battery in an 18V tool?
Not across brands. Milwaukee and Makita each say their batteries work only within their own platforms, whatever the voltage on the label.[3][2]
Are Makita 18V and 40V batteries interchangeable?
No. Makita says 18V LXT batteries go with LXT tools and 40V max XGT batteries with XGT tools.[2]
Does the M18 battery fit M12 tools?
No. Milwaukee says M12 tools take M12 REDLITHIUM packs and M18 tools take M18 REDLITHIUM packs.[3]