Makita Charger Not Charging — Step-By-Step Fixes

1) Safety first (must read)

Danger signs: swollen, leaking, smoking, >50 °C, or burnt smell → do not charge or test. Move outdoors to a non-combustible surface and contact a recycler or hazardous-waste center.
Work on a non-conductive bench. Wear eye protection and insulated gloves when handling terminals or performing load tests.
Never short terminals or pierce packs. Use insulated leads and rated resistors/electronic loads.
If you’re not comfortable with electrical measurements or suspect internal charger faults, stop and use a qualified service.

2) 60-second triage (do these first)

Visual inspection: swelling, cracked/melted plastic, exposed wiring, heavy corrosion → retire the pack.
Power check: plug charger into a known-good outlet; verify outlet with another device.
LED check: observe charger LED patterns with and without a battery inserted. (No LED = no mains / dead charger.)
Swap test: if available, put a known-good Makita battery into the suspect charger. Then put the suspect battery into a known-good Makita charger.

Quick interpretation:

Known-good battery charges normally → charger suspect.
Suspect battery charges in another charger → charger likely problem.
Both fail → proceed with full checks below.

3) Clean & reseat (easy first fix)

Unplug the charger. Clean battery and charger contacts with isopropyl alcohol (≥70%) and a lint-free cloth; dry completely.
Reseat until the latch engages without force. Watch LEDs for several minutes.
Dirty contacts, corrosion, or weak springs cause many “won’t charge” faults.

4) Interpreting common LED behaviours (model-agnostic)

No LED — no power or dead charger.
Solid red — charging normally.
Solid green — full / standby.
Slow red flash — temperature delay (too cold/hot).
Fast red flash / repeated blink — battery fault, BMS lock, or handshake/ID error.
Alternating red/green — conditioning, handshake issue, or unrecognized pack.

Always check the charger manual for model-specific codes.

5) Measure battery open-circuit voltage (OCV)

Tool: digital multimeter.

Field thresholds (practical):

Makita 18V LXT: full OCV ≈ 20.0–21.6 V. Red flag after attempted charge: OCV < ~17–18 V.
Makita 12V CXT: full OCV ≈ 12.4–12.8 V. Red flag: OCV < ~9–10 V.

Set meter to DC volts (≥20 V range for 18 V packs). Record to two decimal places. Very low OCV → deep discharge, BMS lockout, or cell damage.

6) BMS “wake” / recovery attempts (safe sequence)

Some packs enter protection after deep discharge. Try these safe steps in order:

A — Charger wake (safest first)

Place pack on the OEM Makita charger for 10–30 minutes. Many chargers pulse a low current to wake a protected BMS.

B — Tool wake (mild)

Insert pack in a compatible Makita tool and run a light load in short bursts (10–20 s) until the tool cuts out. Rest 30–60 minutes, then retry charging.

C — Alternate OEM charger

Try a different known-good Makita charger if available (different firmware sometimes succeeds).

Do NOT bypass the BMS, apply direct cell charging, or use jury-rigged jump methods — dangerous and warranty-voiding.

Stop and retire the pack immediately if swelling, smell, heat, or odd noises appear.

7) Load / sag test (health check & internal resistance)

Use a real tool under a steady moderate load (recommended) or a properly rated resistor/electronic load. If using a resistor, size it correctly.

Example target: for ~18 V pack aim ~2.0 A load:

R = V ÷ I ≈ 20.00 ÷ 2.00 = 10.00 Ω
Power ≈ V×I = 20×2 = 40 W → use resistor ≥50 W or an electronic load.

Procedure:

Record OCV (e.g., 20.00 V).
Apply load briefly and measure V_load (e.g., 18.20 V).
I ≈ V_load ÷ R (or measure tool current).
ΔV = OCV − V_load. R_internal ≈ ΔV ÷ I.

Rules of thumb (at ~2 A):

Sag ≤ ~1.0 V → healthy.
Sag 1.0–2.0 V → aging/marginal.
Sag > ~2.0 V or collapse toward cutoff → replace pack.

Keep load tests short (10–30 s) and watch for heat.

8) Isolate charger output (if charger suspect)

If comfortable and the manual provides safe test points, measure charger output. Otherwise use swap tests.
If charger shows no output or repeatedly fails with known-good batteries → replace charger.
If output exists but performance is slow/intermittent, SMPS components (caps, controller) may be degraded — replacement is safer than risky repairs unless you’re qualified.

9) Common charger faults & simple fixes

No power / dead LED: check cord, fuse, outlet; replace charger if electronics failed.
Accepts battery but won’t charge: dirty contacts or weak springs — clean or replace bay.
Charger gets very hot: blocked vents or failing internals — stop using and replace.
Intermittent charging: cracked solder or weak springs — professional repair or replace.

10) Advanced checks (experienced technicians only)

Inspect PCB for bulging electrolytics, burnt parts, cracked solder.
Measure bulk capacitor ESR (ESR meter); high ESR → degraded caps.
Check primary fuse continuity with power off.

If you’re not trained in SMPS repair, do not open live electronics — replacement is safer.

11) When to replace battery vs charger

Replace the battery if:

Swollen, leaking, or burnt smell.
Rejected by multiple chargers after wake attempts.
OCV persistently below red flags or large sag under light load.
Drastically reduced runtime after verified full charge.

Replace the charger if:

Known-good batteries fail in it or no LED while the outlet is good.
Persistent internal fault LEDs across good batteries.
Visible thermal/PCB damage, burnt connector, or odor.
Charger overheats without heavy load.

12) Preventive maintenance (reduce recurrence)

Clean contacts monthly on jobsite chargers.
Keep chargers ventilated; don’t cover vents or store near solvents/dust.
Avoid charging in extreme cold/hot — warm packs to ≥5 °C before charging; let hot packs cool to ≤40 °C.
Rotate packs (FIFO) to avoid over-stressing one pack.

13) Final safety note

If you see smoke, flames, hissing, rapid swelling, or persistent burning odor at any point — evacuate, keep people clear, call emergency services if fire develops, and treat the component as hazardous. Do not attempt further diagnostics on a hazardous pack.

FAQ (short)

Q: Why does my charger blink red then green?
A: Often a temperature or handshake condition. Let pack stabilize; run swap tests if persistent.

Q: Can a bad charger damage my Makita batteries?
A: Yes. A malfunctioning charger can supply incorrect voltage or fail to terminate, harming cells or the BMS. Use certified chargers.

Q: How long should a Makita charger last?
A: Many years with care. Premature failure is often from power surges, physical damage, or heavy environmental stress.

Closing

Most “won’t charge” problems are fixed by safe triage: inspect, clean, swap, measure. Only escalate to load tests or advanced diagnostics after those steps. When in doubt — prioritize safety over salvaging a part. Replace suspicious packs and chargers rather than risking people or property.