Makita 6391D has ridden in the truck for years. The chuck still runs true, the two-speed gearbox still clicks in clean — but the battery no longer lasts from smoko to lunch. That is the usual story with this drill. The tool almost never dies first; the pod does. A fresh replacement pack costs a fraction of a new platform kit, and it keeps the whole legacy 18V family working.
Makita 6391D drill battery specifications at a glance
| Specification | Detail |
|---|---|
| Voltage | 18 V |
| Capacity | 3.0 Ah (3000 mAh) |
| Chemistry | Nickel–metal hydride (Ni-MH) |
| Energy | ≈54 Wh (18 V × 3.0 Ah) |
| Replaces part numbers | 1822, 1823, 1833, 1834, 1835, 1835F, PA18, 192826-5, 192827-3, 192828-1, 192829-9, 193061-8, 193102-0, 193140-2, 193159-1, 193783-0 |
| Certification | CE, RoHS |
| Built-in protection | Overcharge, over-discharge, over-current |
| Warranty | 1 year, plus 30-day money-back |
This is an aftermarket replacement tool battery — not a genuine Makita product — built to meet or exceed OEM specifications. The Ni-MH chemistry carries none of the memory effect that plagued older Ni-Cd packs, so it can be topped up whenever suits, with no conditioning cycles.
6391D shares its pod with a wide slice of Makita’s older 18V range, including the 6391DWPE kit variant of the same drill. Representative tools by category:
- Drills and drivers: 6391D, 6391DWPE, 6343D, 6347D, 8443D, 8444D, 6936FD
- Reciprocating saw: JR180D
- Jig saw: 4334D
- Circular saws: 5026D, 5036D, 5046D, 5620DWD, 5621D
- Mitre saws: LS711D, LS800D
- Site gear: BMR100 radio, ML183 torch, UB181D blower
The complete compatibility list is on the product page — worth a check if your tool is not listed above.
Give the new pack a full charge before first use. Makita’s manuals for batteries of this type advise a full initial charge, and it gives you a proper baseline for judging runtime later. Charge on the original-era Makita charger that shipped with the tool, or any Makita power tool battery charger built for this pod platform.
Technical tips for more runtime and longer life
- Favour partial discharges. Run the pack to somewhere around half, then recharge. Ni-MH has no meaningful memory effect, so there is nothing to gain from deep cycles.
- Stop when the tool slows. Forcing a flat pack under load stresses the cells. When the drill starts labouring, swap packs rather than holding the trigger down.
- Rotate two packs on busy jobs. One driving, one cooling and charging. A pack straight off heavy screw-driving wants ten minutes to cool before it goes on the charger.
- Store spares partially charged. A pack heading into months of storage is happier at roughly half charge than full or flat.
Safety essentials
- Do not disassemble, crush or puncture the pack.
- No incineration, and keep the pack away from fire.
- Keep terminals clear of keys, coins and screws — a shorted pack can deliver serious current.
- Keep the pack dry; never charge it wet.
- Store out of reach of children.