Key takeaways
- Milwaukee's own guide gives the M18 HD12.0 at 60 minutes on the Super Charger, 130 on the rapid charger and 241 on the standard charger. The 241 and the two-hour figures that circulate are both right, for different chargers.
- Divide the pack's amp hours by the charger's amps for the fastest a charge could possibly be. A 12 Ah pack on an 8 A charger cannot finish in under 90 minutes.
- Published times run longer than that arithmetic. DeWalt's 6.0 Ah FlexVolt is 60 minutes on an 8 A charger, a third over the 45 minute ideal, because the charger tapers its current as the pack fills.
- Normalized to minutes per Ah, the chargers here run from under 4 to over 45. Makita's DC18RC, DeWalt's DCB118 and Milwaukee's rapid charger sit at 9 to 11, and Milwaukee's standard charger at 20.
- Cold adds time that warming does not give back. DeWalt says a cold pack charges at a slower rate for the whole cycle, and Makita says its listed times can double.
So the two numbers that circulate for a Milwaukee 12.0 are both real. 241 minutes is Milwaukee's figure for the standard charger. The two-hour figure is the rapid charger, which Milwaukee lists at 130 minutes, or DeWalt's 120 minutes for its own 12 Ah pack. The charger in your hand decides which one is yours.
What amp hours and charger amps mean
An amp hour (Ah) is a measure of how much charge a pack holds. A 12 Ah pack is rated to supply 12 amps for one hour, or 6 amps for two. It is a capacity, like the size of a fuel tank. Within one voltage class, Ah compares packs directly. DeWalt's 12Ah FlexVolt and Milwaukee's HD12.0 are both 18 V nominal packs. That is the real rating behind every 20V MAX and M18 label, as is 20V MAX the same as 18V sets out. At 18 V, 12 Ah is 216 Wh, too big to fly as a passenger spare.
A charger's amp rating is how fast it pushes charge back in. An 8 A charger puts in 8 amp hours for every hour it runs at full rate. The size of the tank and the speed of the hose set the time together.
DeWalt adds a rule that matters here. Its battery and charger manual says the rated output current "is the maximum charging rate when used with DeWALT battery packs designed to charge at this rate." So the amp number on a charger is a ceiling, not a promise for every pack. DeWalt rates its DCB118 that way: 8 A for premium packs, 4 A for compact ones.
One more figure makes chargers comparable. Divide the published minutes by the pack's Ah and you get minutes per Ah. That puts a 6 Ah figure and a 12 Ah figure on one scale.
The published times for 12 Ah packs
Milwaukee's come from its Batteries and Charging Solutions Guide, which says they are estimates "based on testing conducted by Milwaukee Tool at room temperature." The UK figures come from the retailer ITS, which says it "collaborated with Milwaukee" on its tables. UK packs and chargers carry different codes from US ones.
| Pack | Charger | Published time | Minutes per Ah | Where it comes from |
|---|---|---|---|---|
| Milwaukee M18 HD12.0 (US) | Super Charger | 60 min | 5.0 | Milwaukee guide |
| Milwaukee M18 HD12.0 (US) | Rapid charger | 130 min | 10.8 | Milwaukee guide |
| Milwaukee M18 HD12.0 (US) | Standard charger | 241 min | 20.1 | Milwaukee guide |
| Milwaukee HB12 (UK) | M12-18SC Super Charger | 60 min | 5.0 | ITS with Milwaukee |
| Milwaukee HB12 (UK) | M12-18FC rapid | 130 min | 10.8 | ITS with Milwaukee |
| Milwaukee HB12 (UK) | M12-18C | 250 min | 20.8 | ITS with Milwaukee |
| Milwaukee HB12 (UK) | M12-18AC | 330 min | 27.5 | ITS with Milwaukee |
| Milwaukee FORGE FB12 (UK) | M18 DBSC | 45 min | 3.75 | ITS with Milwaukee |
| Milwaukee FORGE FB12 (UK) | M12-18C | 250 min | 20.8 | ITS with Milwaukee |
| DeWalt DCB612 FlexVolt 12Ah | Not named | 120 min | 10.0 | DeWalt product page |
The UK HB12 lines up with the US HD12.0 on the Super and rapid chargers, 60 and 130 minutes each. The UK M12-18C lists 250 minutes, close to the 241 Milwaukee gives in the US for its standard charger. The FORGE FB12 has the fastest time in any table here, 45 minutes on the M18 DBSC. Yet the same pack takes 250 minutes on the M12-18C. The pack sets the ceiling. The charger sets the time.
DeWalt's page gives 120 minutes and names no charger. A 4 A charger cannot do it, because 12 / 4 is three hours even at full rate. And 120 minutes for 12 Ah is 10 minutes per Ah, the same rate DeWalt's DCB118 manual gives for the 6.0 Ah FlexVolt (60 minutes). On a slower DeWalt charger, plan on longer.
Makita's 18V LXT charger documents checked here stop at 6.0 Ah. They list no 12 Ah pack, so Makita appears in the next table by rate, not by a 12 Ah time.
Every charger in minutes per Ah
Here the three makers line up on one scale. Each row is a published time divided by the pack's Ah. Milwaukee's figures are for the HD12.0. DeWalt's come from the charge time matrix in its DCB118 manual, for the DCB606 6.0 Ah FlexVolt. Makita's come from its DC18RC product page, for the BL1860B 6.0 Ah.
| Maker and charger | Pack used | Published time | Minutes per Ah | Time for 12 Ah at that rate |
|---|---|---|---|---|
| Milwaukee M18 DBSC (UK) | FB12 12.0 Ah | 45 min | 3.75 | 45 min, published |
| Milwaukee Super Charger | HD12.0 | 60 min | 5.0 | 60 min, published |
| Makita DC18RC | BL1860B 6.0 Ah | 55 min | 9.2 | 110 min |
| DeWalt DCB118 | DCB606 6.0 Ah | 60 min | 10.0 | 120 min |
| Milwaukee rapid charger | HD12.0 | 130 min | 10.8 | 130 min, published |
| DeWalt DCB115 | DCB606 6.0 Ah | 90 min | 15.0 | 180 min |
| Milwaukee standard charger | HD12.0 | 241 min | 20.1 | 241 min, published |
| DeWalt DCB112 | DCB606 6.0 Ah | 170 min | 28.3 | 340 min |
| DeWalt DCB107 | DCB606 6.0 Ah | 272 min | 45.3 | 544 min |
The scale runs from under 4 minutes per Ah to over 45. That twelvefold spread is the whole answer to "how long."
Why real times run longer than Ah divided by amps
Take the DCB118's own numbers. DeWalt rates it at 8 A for premium packs and says it charges the 6.0 Ah FlexVolt in 60 minutes. The formula gives 6 / 8 = 0.75 hours, or 45 minutes. The published time is 15 minutes longer, a third over the floor. Four things add that time.
The charge slows near the top. Lithium-ion packs charge in two stages. First the charger pushes a steady current. Then it holds the voltage steady and the current falls. Battery University says full charge comes when the current has dropped "to between 3 and 5 percent of the Ah rating." That last stretch runs at a fraction of the charger's rating, and it is where the extra time goes.
A faster charger does not shorten that tail. Battery University also says that with higher current, the first stage is shorter "but the saturation during Stage 2 will take longer accordingly." A high current charge will "quickly fill the battery to about 70 percent." This is why the 80 percent figure is the useful one on a fast charger. DeWalt's 12 A DCB1112 brings a 9.0 Ah FlexVolt to 80 percent "in under 45 minutes." The arithmetic floor for that 7.2 Ah is 36 minutes. The last 20 percent of the pack is where the rest of the time goes.
The pack has to accept the current. DeWalt's matrix shows it plainly. On the DCB118, a DCB205 5.0 Ah pack takes 75 minutes, or 47 minutes for packs with a date code of 201536 or later. Same charger, same capacity, different packs. Only the second figure comes near the 8 A floor of 37.5 minutes. The DCB204 4.0 Ah shows the same split, 60 minutes or 40. The newer figures run 1.25 and 1.33 times the 8 A floor, close to the FlexVolt's extra third.
Temperature changes everything. Milwaukee's guide says its chargers optimize "charge rates based on the battery type and temperature." DeWalt's DCB118 manual goes further: "A cold battery pack will charge at a slower rate than a warm battery pack." It adds that the pack "will charge at that slower rate throughout the entire charging cycle and will not return to maximum charge rate even if the battery pack warms." A pack too hot or too cold waits in a Hot/Cold Pack Delay before it charges at all. Makita's manual says its times may take "twice the above charging time to the maximum," because of temperature, pack condition and maintenance charge.
Heat works from the other side. Makita's DC18RD fan cools a hot pack before charging starts. If the fan cannot keep up, Makita warns that "the charging time will be longer than usual." DeWalt fits the DCB118 with a fan for the same reason.
One more trap: chargers with several ports
A charger with more than one port may not charge them at once. Milwaukee's guide lists a Six Pack Sequential Charger, and the name says how it works. Packs take turns, so the last pack waits for every pack before it. Makita's DC18RD is built the other way. Makita says it "charges two (2) 18V LXT Lithium-Ion 6.0Ah batteries in only 55 minutes," the same time the DC18RC gives for one. Check whether a multi-port time is per pack or for the set.
A worked case: what a lunch break puts back
Take an M18 HD12.0 that has run flat by noon. Suppose there is a 30 minute lunch break and one charger on site. How much of the pack comes back depends on which charger it is.
Use Milwaukee's published minutes per Ah and divide 30 minutes by each rate:
| Charger | Minutes per Ah | Ah back in 30 minutes, at the average rate | Share of 12 Ah |
|---|---|---|---|
| Standard charger | 20.1 | 1.5 Ah | 12% |
| Rapid charger | 10.8 | 2.8 Ah | 23% |
| Super Charger | 5.0 | 6.0 Ah | 50% |
Worked through, the standard charger puts back about an eighth of the pack. The Super Charger puts back about half. This uses the average rate across the whole charge. The early part of a charge runs at full current, and the slow tail comes last. So the real first 30 minutes should do at least this well, not worse. A pack from a cold truck is the exception. On DeWalt's rule, a cold pack stays slow for its whole charge, so warm it first. The battery storage temperature guide gives each brand's charging floor.
Now suppose the same pack goes on at 5 pm in a heated shop. Even the standard charger's 241 minutes is done by about 9 pm. Overnight, charger speed barely matters. It matters when the charge has to fit inside a working day.
Which number is yours
| Your setup | Plan on | Why |
|---|---|---|
| Milwaukee HD12.0, standard charger | About 4 hours (241 min) | Milwaukee guide |
| Milwaukee HD12.0, rapid charger | About 2 hours (130 min) | Milwaukee guide |
| Milwaukee HD12.0, Super Charger | 1 hour (60 min) | Milwaukee guide |
| Milwaukee FORGE 12.0, M18 DBSC (UK) | 45 min | ITS with Milwaukee |
| DeWalt DCB612 12Ah | 120 min, charger not named | DeWalt product page |
| Any 12 Ah pack, charger amps known | At least Ah / amps, likely about a third more | DCB118's 6.0 Ah figure against its 8 A rating |
| Cold pack (Makita's charging floor is 50 F, 10 C) | Longer than any figure above | DeWalt and Makita manuals |
For a charger not listed here, find its published time for any pack, divide by that pack's Ah, and multiply by 12. If the maker gives the charger's amps instead, 12 divided by the amps is the fastest it can be.
Where this answer stops applying
These are the makers' estimates. Milwaukee says its figures come from its own testing at room temperature and that "actual results may vary." DeWalt's matrix says all charge times are approximate. None of the documents says what charge level the pack started from. The table covers Milwaukee, DeWalt and Makita 18 V class packs only. Other brands, 12 V packs, aftermarket chargers and chargers run from a vehicle are outside it. The scaled rows in the minutes per Ah table are this site's arithmetic on 6.0 Ah figures, not maker figures for 12 Ah packs. Nothing here says whether fast charging shortens a pack's life. Milwaukee says its chargers choose rates for "the best combination of charge time and pack life," and none of the three gives a number for it. Charging also has hard temperature limits. Makita's manual says not to charge when the room is below 50 F (10 C) or above 104 F (40 C). DeWalt's DCB118 manual sets 40 to 104 F (4.5 to 40 C) and says keeping inside it "will prevent serious damage to the battery pack." Why cold charging does that damage is covered in can you leave tool batteries in a cold garage. The manual for your own charger and pack overrides every figure here.
The thirty-second check
- Find your charger's published time for your pack. If the maker lists it, that is your answer at room temperature.
- If not, divide any published time for that charger by the pack's Ah, then multiply by 12.
- If you only know the charger's amps, 12 divided by the amps is the floor. Add about a third.
- If the pack is cold, warm it before it goes on. A cold start stays slow to the end.
- On a multi-port charger, check whether the ports charge at once or take turns.