Specs from the makers' own documentation Battery compatibility built in UK retailer prices, updated daily 25+ years of trade experience
‹ All Milwaukee M12 batteries
M12 Milwaukee M12B4
Fits
35 Milwaukee M12 toolsSee them ›
Charges
52 min on 2 of the 5 chargers Milwaukee lists for itCharge times ›
Specs
From Milwaukee's own documentationChecked 24 Sep 2026
Milwaukee · M12 platform

Milwaukee M12B4 12V 4.0Ah REDLITHIUM battery

4.0Ah 48Wh 0.4kg Fuel gauge

Milwaukee M12 REDLITHIUM 4.0Ah pack. 0.4kg.

Adds it to My Tools, kept on this device
Lowest price we track
£39.95at Tooled Up · + £6.95 delivery
View at Tooled Up ›
Compare retailersTotal with delivery
Tooled Up Lowest£39.95 + £6.95 delivery£46.90View ›
My Tool Shed£39.95 + £6.95 delivery£46.90View ›
Prices from UK retailer feeds, updated daily.We may earn a commission
4.0AhCapacitymaker figure
48WhEnergymaker figure
0.4kgWeightmaker figure
120Wh/kgEnergy for its weightworked out
£9.99Per Ahat the lowest price we track

Other sizes in this range

Same fit, same tools. Bigger packs run longer and weigh more. Pick the size for the job.

Compare these sizes ›All Milwaukee M12 batteries ›
ModelSizeEnergyWeightLowest pricePer Ah
M12B2 2.0Ah 24Wh 0.2kg £25.95 £12.98 per Ah
M12HB2.5 2.5Ah 30Wh 0.2kg £32.95 £13.18 per Ah
M12B3 3.0Ah 36Wh 0.2kg £29.95 £9.98 per Ah
M12B4 This one 4.0Ah 48Wh 0.4kg £39.95 £9.99 per Ah
M12HB5 5.0Ah 60Wh 0.42kg £59.95 £11.99 per Ah
M12B6 6.0Ah 72Wh 0.4kg £49.95 £8.33 per Ah

Prices are the lowest we track at UK retailers, updated daily. Weights from Milwaukee. Energy is Milwaukee's figure, or worked out from volts × Ah where they don't publish one.

Full specs

From Milwaukee's own documentation, checked 24/09/2026. "Not listed" where Milwaukee doesn't publish a figure.

Voltage12V
Capacity4.0Ah
Energy48Wh
ChemistryLi-ion (cylindrical)
Cell typeNot listed
Weight0.4kg
Size (L × W × H)Not listed
Fuel gaugeYes
ExtrasREDLINK Intelligence
PlatformMilwaukee M12
Model codeM12B4

Charge times

Milwaukee's own figures, fastest first. Each charger opens its own page.

M12-18FCMulti-voltage fast charger
52 min
£59.95 at Tooled Up ›
M12-18GBC4Four-bay gangbox charger (2 at once)
52 min
No retailer price yet
C12CCharger
1 hr 20 min
£44.95 at Tooled Up ›
M12C44-bay sequential charger
1 hr 20 min
£78.95 at Tooled Up ›
M12-18ACIn-car charger
1 hr 55 min
£79.95 at Tooled Up ›

Milwaukee's own figures. We may earn a commission

Fits these tools

Every Milwaukee M12 tool takes this pack. It won't fit other brands' tools.

All 35 Milwaukee M12 tools ›
Ratchets11 tools › Drill Drivers4 tools › Multi-Tools2 tools › Reciprocating Saws2 tools › Belt Files2 tools › Random Orbital Sanders2 tools › Combi Drills2 tools › Rotary Polishers1 tool › Detail & Delta Sanders1 tool › Mini & Spot Repair Sanders1 tool › Planers1 tool › Brad Nailers1 tool › Jigsaws1 tool › Handheld Vacuums1 tool › Site Vacuums1 tool › Angle Drills1 tool › Circular Saws1 tool ›

4.0Ah packs from other brands

Only useful if you haven't picked a platform yet: packs don't swap between brands. Shown on neutral figures only.

Not sure which platform? ›
BatteryEnergyWeightWh per kgLowest pricePer Ah
MilwaukeeM12B4 48Wh 0.4kg 120 £39.95£9.99
MakitaBL1041B 43Wh 0.38kg 114 £49.00£12.25

M12B4 questions

Which tools does the M12B4 fit?

It fits every Milwaukee M12 tool. It won't fit other brands' tools.

How long does the M12B4 take to charge?

From Milwaukee's own figures: M12-18FC: 52 min, M12-18GBC4: 52 min, C12C: 1 hr 20 min, M12C4: 1 hr 20 min, M12-18AC: 1 hr 55 min.

Scroll to Top