Quick answer
The most misread Ryobi charger signal is a blinking red LED — on 18V ONE+ chargers (P118/P119), a blinking red means the charger is evaluating the pack, not that the pack is dead. On 40V chargers (OP405A/OP406), a fast alternating red and green is the actual fault indicator. Before replacing anything, confirm which platform you have and match the LED pattern to the table below.
LED code decoder by platform
18V ONE+ chargers (P117, P118, P118B, P119)
The P118/P118B/P119 are the most common 18V ONE+ chargers. Their LED logic uses one red LED and one green LED.
| LED pattern | What it means | Action |
|---|---|---|
| Red solid, green off | Pack accepted — normal charging in progress | Wait for charge to complete |
| Red flashing, green off | Evaluate mode — charger is testing the pack | Wait up to 30 minutes at room temp |
| Red off, green flashing | Charging nearly complete | Wait |
| Red off, green solid | Fully charged | Use the pack |
| Red fading (pulses slowly) | Pack is defective — BMS rejected it | Replace the pack |
| No LEDs | No AC power, or charger fault | Check outlet; test with known-good pack |
The 30-minute Evaluate rule (per Ryobi P119 manual): If the charger stays in Evaluate (red flashing, green off) for longer than 30 minutes at room temperature, the pack is likely defective. This rule applies to P118, P118B, and P119 chargers. It does NOT apply to P117, which uses different logic for its dual-chemistry (NiCd + Li-Ion) design.
40V chargers (OP405A, OP406, OP406A)
| LED pattern | What it means | Action |
|---|---|---|
| Solid red + solid green | Thermal lockout — pack too hot or too cold | Cool or warm the pack; charging resumes automatically |
| Slow red flash (no green) | Pack voltage too low, or communication issue | Try a recovery charge; replace if it persists |
| Fast alternating red/green | Defective pack — BMS detected a bad cell | Replace the pack |
| No LEDs | No power or charger fault | Check outlet; test charger with a second pack |
Note on the battery's own LED: Ryobi 40V packs have fuel-gauge LEDs on the side of the pack, separate from the charger. A single red or orange LED on the pack means low battery — charge it. That is not a fault.
Common causes and fixes
Red light blinking on 18V ONE+ charger — Evaluate mode
When a P118/P119 charger sees a blinking red LED with the green LED off, it is in Evaluate mode. This happens when:
- The pack is deeply discharged and the charger is running a recovery cycle (can take 15–25 minutes)
- The pack is cold and below the charging threshold
- The pack's BMS is reporting a cell imbalance
What to do:
- Move the pack and charger to room temperature (65–75°F) if either is cold
- Wait a full 30 minutes from when you inserted the pack
- If the LED transitions to solid red (charging) or solid green (full), the pack is fine
- If the LED stays in red-flashing after 30 minutes at room temperature, the pack is defective
40V battery flashing red — charger vs pack fault
On the 40V platform, the LED pattern tells you whether the charger or the pack is bad:
- Remove the pack you're testing. Note the exact LED pattern (slow flash, fast alternating, solid with another color).
- Insert a second known-good 40V pack into the same charger. If the second pack charges normally, the original pack is bad. If the second pack also faults, the charger may be bad or unplugged.
- Test the suspect pack on a second charger (borrow from a neighbor, or test at the Home Depot tool rental counter). If the suspect pack faults on every charger you try, the pack is definitively bad.
Clean both the pack rails and charger contacts with a microfiber cloth before testing. Grit and corrosion cause handshake failures that look exactly like a dead pack.
Battery won't charge — cold weather
Ryobi's 18V ONE+ BMS refuses to charge below approximately 32°F (0°C). The 40V platform refuses below approximately 32°F as well, but the thermal lockout on the 40V charger displays as a solid red + solid green rather than a pure fault signal.
Fix: Bring the pack indoors to 65–75°F. Wait 30–60 minutes. Do not use a heat gun, oven, or direct heat source — uneven heating damages cells. Once the pack feels room-temperature to the touch on all surfaces, reinsert it. Charging should resume automatically.
Cold weather tip: Store batteries indoors overnight. Bring them out charged for the day's work. Repeated attempts to charge cold packs can cause lithium plating that permanently reduces capacity.
Charger stuck in Evaluate mode past 30 minutes
If you have verified the pack is at room temperature and the P118/P119 charger has been in Evaluate mode (red flashing, green off) for more than 30 minutes, run the confirmation test:
- Remove the suspect pack.
- Insert a different known-good 18V ONE+ lithium-ion pack.
- If the second pack transitions normally (solid red or green within a few minutes), the original pack is defective.
- If the second pack also stays in Evaluate, check the charger contacts for corrosion and test on a different outlet.
Also confirm the pack is a genuine Ryobi 18V ONE+ lithium-ion battery (P-prefix SKUs like P102, PBP004, P190). Third-party "compatible" packs frequently fail to communicate with Ryobi's BMS firmware, causing persistent Evaluate mode.
Pack not holding a charge after it shows "full"
If the charger reaches solid green (fully charged) but the pack runs tools for only a few seconds before quitting, one or more cells have lost capacity. The BMS shows "charged" but actual usable capacity is near zero. This is end-of-life behavior — the pack needs replacement, not a reset.
18V and 40V batteries are NOT interchangeable
Never force a Ryobi 18V ONE+ pack into a 40V charger or vice versa. The platforms use different voltages, different BMS communication protocols, and different physical connectors. An adapter does not exist that safely bridges the two.
Isolating charger fault vs pack fault
When you cannot tell whether the charger or the pack is bad, use the cross-test:
- Pack is bad if: the same pack faults on two different chargers, and a second known-good pack works on your original charger
- Charger is bad if: multiple different packs all fault on the same charger, but those same packs work fine on another charger
If it still isn't working
Under warranty: Ryobi offers a 3-year warranty on 18V ONE+ lithium-ion batteries and a 3-year warranty on 40V HP batteries. Register at ryobitools.com or check purchase history through your Home Depot Pro Xtra account. Home Depot handles most Ryobi warranty exchanges in-store, often without requiring mail-in service.
Over warranty with visible damage (swelling, cracking, leaking): Do not use. Recycle at any Home Depot, Lowe's, or Call2Recycle drop-off location. They accept lithium-ion packs for free.
Over warranty with no visible damage: Many Ryobi packs run 3–6 years with moderate use. If the pack passes the cross-test (charges fine on a second charger), the original charger may be the failing component.
For a replacement 18V ONE+ pack:
View Ryobi 18V ONE+ HP 4.0Ah Battery (PBP004) on Amazon (paid link)
View Ryobi 18V ONE+ HP 4.0Ah Battery (PBP004) on Home Depot (paid link)
For a replacement 40V HP pack:
View Ryobi 40V 4.0Ah HP Battery (OP40404) on Amazon (paid link)
View Ryobi 40V 4.0Ah HP Battery (OP40404) on Home Depot (paid link)
FAQ
What does a blinking red light mean on my Ryobi charger?
On the P118/P119, a blinking red with green off means the charger is in Evaluate mode — assessing the pack before starting a full charge. This is normal for the first few minutes. If it lasts longer than 30 minutes at room temperature, the pack is likely defective per Ryobi's P119 manual.
Can I charge my Ryobi battery in cold weather?
Ryobi's 18V ONE+ BMS refuses to charge below approximately 32°F (0°C). The 40V platform shows a thermal lockout (solid red + solid green on the charger) below approximately 32°F. Bring the pack indoors to room temperature first.
Why does my Ryobi 40V charger flash red and green alternately?
Fast alternating red and green on the 40V charger (OP405A/OP406) is the defective pack signal — the BMS has detected a bad cell. Confirm with the cross-test using a second pack before replacing anything.
Do Ryobi 18V batteries work in Ryobi 40V chargers?
No. The 18V ONE+ and 40V platforms are not cross-compatible. Different voltages, different connectors, different BMS protocols.
What should I do with a swollen Ryobi battery?
Stop using it immediately. Swollen packs are a safety hazard — they indicate internal cell gassing. Recycle at Home Depot, Lowe's, or a Call2Recycle drop-off. Do not put lithium-ion packs in regular trash or curbside recycling.
How long should a Ryobi 18V battery last?
Expect 500–800 charge cycles to approximately 80% of original capacity with normal use. That is 3–5 years for weekend use, or 1–2 years for heavy daily contractor use. Storing packs at 50% charge in a cool, dry location extends lifespan.
What is the Ryobi 18V ONE+ warranty?
3 years for lithium-ion batteries purchased in the US. The 40V HP batteries also carry a 3-year warranty. Proof of purchase is required. Register at ryobitools.com or verify through your Home Depot purchase history.