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Red LED flashing

Ryobi Red LED flashing on RC18120 charger: evaluate mode

Verified with sources1 sourceReviewed Oct 18, 2026
Technician coming? See the 2 steps they must show you
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Risk level

Low

Usually safe to check without specialist tools.

Urgency

Low

Quick answer

On the Ryobi 18V ONE+ RC18120 charger, a flashing red LED with the green LED off indicates Evaluate status: the battery pack is hot, cold, or deeply discharged. Placed indoors between 10 °C and 38 °C, the charger automatically switches to fast charge mode once ready.

Safety first

Stop and check this first

  • Hazardous voltages are present within the RC18120 charger (equipped with a 2 A time-lag fuse): never modify, disassemble or attempt to repair the product yourself, never recharge primary (non-rechargeable) cells or nickel cadmium (NiCd) battery packs (when a NiCd battery pack is inserted, the red LED will light up and green LED will be off), and never charge damaged or leaking batteries.
  • Use the charger indoors in dry conditions only, never operate it on a combustible surface or near flammable materials (cloth, packaging, paint, spray paint or aerosols, lubricant, thinners, petrol or gas containers), and remove the charger plug from the power socket and take the battery off when not in use.

Safe checks you can perform

  • Let a hot battery pack cool for approximately 30 minutes or wait on the charger
  • Place the battery pack and RC18120 charger indoors between 10 °C and 38 °C
  • Allow pre-charging and verify the transition to fast charge and full charge

Leave these tasks to a qualified professional

  • Do not attempt this professional task: Professional repair or supply cord replacement at an authorised Ryobi service centre
  • Do not attempt this professional task: Electrical check of both battery pack and RC18120 charger at an authorised service center

What a technician must be able to justify

Technician visit

These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.

These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.

  1. Professional repair or supply cord replacement at an authorised Ryobi service centre

    What they doIf the product enclosure, cable or adaptor plug is damaged or the RC18120 charger has an internal failure, the manufacturer, its service agent or an authorised Ryobi service centre performs the replacement or professional repair.

    They must show youthe repaired or replacement RC18120 charger showing Red LED ON and Green LED OFF when plugged in without a battery pack.

    In writingthe service report for the repaired or replaced RC18120 charger or supply cord.

  2. Electrical check of both battery pack and RC18120 charger at an authorised service center

    What they doIf the RC18120 charger does not charge your battery pack under normal circumstances within the specified temperature range, both the battery pack and the charger are returned to the nearest authorised Ryobi service center for an electrical check.

    They must show youthe charger switching from Evaluate to Fast charging (Red LED ON, Green LED Flashing) and the electrical check result.

    In writingthe electrical check findings for both the battery pack and the RC18120 charger.

Before accepting a part or repair

Nothing has been shown yet. Do not accept a part swap based on the code alone.

Follow these steps

Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.

  1. Let a hot battery pack cool for approximately 30 minutes or wait on the charger

    No special tools

    Who:
    you, in a dry indoor spot away from sunlight and heat sources.
    How:
    if the battery pack became hot from using a tool continuously, the Charging a Hot Battery Pack section of the RC18120 manual states that you should let a hot battery pack cool down for approximately 30 minutes before attempting to recharge (or if already seated in Evaluate mode, allow it to reach a cooled temperature), keeping the charger out of sunlight or other heat sources.
    Result that matters:
    the battery pack reaching a cooled temperature so the RC18120 charger begins fast charge mode (Red LED ON, Green LED Flashing).
    If it switches to Red LED ON and Green LED Flashing once cooled:
    the flashing red LED was normal hot-pack evaluation.
    If the battery pack was not hot from use:
    check the room temperature and deep-discharge pre-charge stage next.
    Evidence to keep:
    how long the pack cooled after tool operation and the change in the red and green LEDs.

    Evidence: Ryobi RC18120 18V ONE+ Charger Original Instructions (961152721-02)

  2. Place the battery pack and RC18120 charger indoors between 10 °C and 38 °C

    No special tools

    Who:
    you, checking the charging and storage room temperature.
    How:
    place the battery pack and RC18120 charger indoors in dry conditions where the temperature is more than 10 °C but less than 38 °C, on a non-combustible surface with all ventilating slots uncovered (the Storage section recommends storing the charger in a cool dry place between 10 and 25 °C and not leaving it in a vehicle during hot or cold conditions).
    Result that matters:
    a cold battery pack reaching a warmed temperature so the charger begins fast charge mode automatically.
    If fast charging starts once warmed between 10 °C and 38 °C:
    avoid storing the charger or battery in a hot or cold vehicle.
    If the room is already between 10 °C and 38 °C and the red LED keeps flashing with green off:
    allow pre-charging to finish.
    Evidence to keep:
    the room temperature where the RC18120 charger is plugged in.

    Evidence: Ryobi RC18120 18V ONE+ Charger Original Instructions (961152721-02)

  3. Allow pre-charging and verify the transition to fast charge and full charge

    No special tools

    Who:
    you, observing the red and green LEDs on the RC18120 charger.
    How:
    press down on the battery pack to be sure contacts on the battery pack engage properly with contacts in the charger connected to 220-240 V (50/60 Hz). If deeply discharged, allow the RC18120 to pre-charge the pack to normal voltage and watch for Fast charging (Red LED ON, Green LED Flashing) followed by Full / Charging complete (Red LED OFF, Green LED ON).
    Result that matters:
    the battery completing its approximate charging time on the RC18120 (such as 40 minutes for RB18L13 1.3 Ah, 60 minutes for RB18L20 2.0 Ah, or 150 minutes for RB18L50 5.0 Ah).
    If it enters fast charging and finishes with Red LED OFF and Green LED ON:
    pre-charging restored normal voltage.
    If the charger does not charge your battery pack under normal circumstances or both LEDs flash:
    return both the battery pack and charger for an electrical check.
    Evidence to keep:
    the compatible battery model (such as RB18L13, RB18L20, or RB18L50) and the final LED states.

    Evidence: Ryobi RC18120 18V ONE+ Charger Original Instructions (961152721-02)

Still not solved

If the error persists, stop here. See what the technician must do and show you.

Where this code applies

A code is meaningful only inside the right product and version context.

Primary scope

System
Garden
Brand
Ryobi
Product type
Cordless garden tools

Known code variants

  • Cargador Ryobi RC18120 luz roja parpadeando
  • Cargador Ryobi RC18120 modo prueba
  • RC18120 indicador rojo parpadeante y verde apagado
  • RC18120 red LED flashing
  • Red LED flashing
  • Ryobi hot or cold battery pack light
  • Ryobi LED rojo parpadeante y verde apagado
  • Ryobi ONE+ batería demasiado caliente o fría
  • Ryobi ONE+ RC18120 evaluate mode
  • Ryobi RC18120 charger flashing red light
  • Ryobi red LED flashing green LED off

What it means

Ryobi original instruction manual 961152721-02 for the RC18120 charger (18 V, 220-240 V 50/60 Hz, 60 W) defines Red LED Flashing with Green LED OFF as the Evaluate indicator. In this state, when a hot battery pack reaches a cooled temperature or a cold battery pack reaches a warmed temperature, the charger begins fast charge mode; if the battery pack is deeply discharged, the charger pre-charges the battery until normal voltage is reached and then begins fast charge mode. Other models may differ, and a flashing red LED alone does not prove a part is faulty.

Warnings and stop conditions

  • Highsource verified

    Hazardous voltages are present within the RC18120 charger (equipped with a 2 A time-lag fuse): never modify, disassemble or attempt to repair the product yourself, never recharge primary (non-rechargeable) cells or nickel cadmium (NiCd) battery packs (when a NiCd battery pack is inserted, the red LED will light up and green LED will be off), and never charge damaged or leaking batteries.

    Evidence: Ryobi RC18120 18V ONE+ Charger Original Instructions (961152721-02)

  • Mediumsource verified

    Use the charger indoors in dry conditions only, never operate it on a combustible surface or near flammable materials (cloth, packaging, paint, spray paint or aerosols, lubricant, thinners, petrol or gas containers), and remove the charger plug from the power socket and take the battery off when not in use.

    Evidence: Ryobi RC18120 18V ONE+ Charger Original Instructions (961152721-02)

Symptoms and causes

Probable causes · in order

  • Hot battery pack after using a tool continuouslyCommon

    Manual 961152721-02 for the RC18120 charger explains that when using a tool continuously, the cells in the battery pack become hot, and the charger waits in Evaluate mode (Red LED Flashing, Green LED OFF) until the pack reaches a cooled temperature.

    Evidence: Ryobi RC18120 18V ONE+ Charger Original Instructions (961152721-02)

  • Cold battery pack or ambient temperature outside 10 °C to 38 °CPossible

    Ryobi instructs you to place the battery pack and RC18120 charger in an area where the temperature is more than 10 °C but less than 38 °C; a cold battery pack stays on flashing red until it reaches a warmed temperature.

    Evidence: Ryobi RC18120 18V ONE+ Charger Original Instructions (961152721-02)

  • Deeply discharged battery pack being pre-charged to normal voltagePossible

    According to the LED charge indicator table in manual 961152721-02, Red LED Flashing with Green LED OFF also occurs while the charger pre-charges a deeply discharged battery until normal voltage is reached.

    Evidence: Ryobi RC18120 18V ONE+ Charger Original Instructions (961152721-02)

Virtual technician

Does Red LED flashing still appear after these checks?

Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.

Start diagnosis

Sources and technical references

  1. 1

    Ryobi RC18120 18V ONE+ Charger Original Instructions (961152721-02)

    Ryobi · 2015 · official_doc

Sources: Ryobi RC18120 18V ONE+ Charger Original Instructions (961152721-02)reviewed 2026-10-18 · verified

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