Ryobi battery not charging fix and flashing red

For the home handyman, Ryobi 18v tools are of excellent value. They have the biggest range and are well-built. But occasionally over time, the genuine Ryobi lithium 18v batteries will fail to charge.

If your Ryobi battery says fully charged but won’t work then you have an issue with the battery itself. This is not a common issue but can be frustrating and expensive if your batteries stop charging and are defective.

The reason that these batteries fail to charge is down to the internal charging circuit on each battery. This integrated motherboard circuit tells the charger when to stop charging and prevents over-discharging from your power tool.

Internal charging circuit of Ryobi 18v P108 battery 4ah
The internal charging circuit of Ryobi 18v P108 battery 4ah

Often the Ryobi batteries won’t charge because they have been left fully discharged or flat for a long period of time. The 18v+ battery will continue to discharge slowly over time.

Once they get under 11v or less the battery charger will fail to charge the battery. This will often give you the dreaded red blinking LED with a green light soon after.

In this post, we will show you how to fix a Ryobi battery that won’t charge and show you the possible reasons why it happens.

Ryobi Battery Charger Not Working

If your Ryobi battery charger is failing to charge the battery it could be due to a number of reasons.

  • Is there mains power to the battery charger?
  • Do you have the Ryobi battery fully inserted into the charger?
  • Have you let the battery cool down after running in a power tool?
  • Turn on the charger before inserting the battery.
  • Is the moisture or dirt on the battery contacts?
  • Is the battery over-discharged eg: less than 11v
  • Has a battery’s internal cables become dislodged?
  • The Ryobi battery is defective

How To Revive Ryobi Batteries

how to revive ryobi batteries and open up a One+ 18v battery using Torx T10
A Torx T10 bit it required to open up Ryobi batteries.

The reason these lithium battery packs usually fail is one or more of the internal lithium cells have a low voltage. This will pull down the whole pack voltage to where the charger thinks it is unsafe to charge.

We can fool the charger by temporally increasing the internal voltage using some alligator clips and the stock charger or using a 12v smart car charger.

Jump Start Ryobi Battery

To try and revive Ryobi batteries you will have to disassemble the battery by removing the 5 torque screws using a T10 security Torx screwdriver. A battery drill makes this process faster as the screws are long.

Note this will void any warrenty on the battery.

To pull out the whole internal battery pack you will also need to remove the two battery spring clamps. These hold the battery to the power tool. They will slide out easily.

Locate the positive connection point and the negative connection point for the battery pack. This is where we will attach the jump start fly leads.

Positive will be on one side of the battery pack and negative will be on the other side.

how to Fix a Ryobi Battery that Won't Charge jump start termainals
Attach fly leads to these contacts on the Genuine Ryobi flat battery.

Make sure to only charge this Ryobi battery pack for around 30 seconds or less. We are not trying to fully charge this faulty 18v battery. Only need to raise the voltage to over 11v DC.

Inside a Ryobi Battery How to fix a dead One + battery
Powilling Aftermarket 18v Ryobi battery opened up to show the internal circuit.

The following video shows how to repair an 18v Ryobi P102 battery that is not charging.

It is no wonder people like to fix these batteries due to the huge cost of buying genuine Ryobi 18v One + batteries.

I have had great success with using the cheaper aftermarket Ryobi 18v One Plus 6AH batteries. They are just as powerful, have longer run times, and often 1/2 the price of a genuine battery.

They are compatible with Ryobi p102, p103, p104, p105, p107, p108, p109 and fit all Ryobi 18v one+ system cordless tools.

Why Is My Ryobi Battery Charger Blinking Red?

The reason your battery charger is blinking red is due to the condition of the 18v+ battery. It could be because of the following reasons. Sometimes you will also have a Ryobi battery charger flashing red and green LEDs.

  • Over discharged.
  • Battery over temperature.
  • Failed internal cells.
  • Faulty battery integrated circuit.
  • Broken internal cable.
  • Moisture in the battery.

Most of the time it is a single battery cell that is low on voltage. Raising its voltage is the only way how to fix a Ryobi battery that won’t charge.

Can Ryobi batteries be left on a charger?

Yes, they can be safely left on the charger when completely charged. Although the safest standard is to turn off the power to the charger and remove the battery once it is at full capacity.

I remove each battery once I see the green light come on steady on the charger. This means my batteries are fully charged. If you forget to take the battery out for a few days no damage will occur.

Ryobi battery says fully charged but won’t work.

If the green light comes on as soon as you have plugged in the battery you most probably have one or more defective cells inside the battery pack. You will have to replace the battery or open up the battery pack to find the faulty cell and try and jumpstart it.

Another possible reason is a solder joint has come loose inside the battery pack. This can happen if the battery is dropped. You will need to open up the battery pack and look for a loose cable or battery solder joint.

Internal Ryobi One + Lithium Cells

Depending on the size of the Ryobi battery you could have 5-10 lithium 18650 cells inside. These will be wired up in a combination of series and parallel. One of my batteries had LGDAHB21865 cells inside. These are LG (Lifes Good lithium batteries)

How To Revive Ryobi Batteries bank of 10 lithium-ion batteries

Looking at the datasheets for these 18650 batteries the minimum voltage is between usually 2.0 and 3.0 volts. The internal protection circuit on these Ryobi batteries disables the cell at 2.5 volts.

18650 lithium-ion batteries are charged up to 4.2V and down to between 2V and 3V depending on the cell’s specification for cut-off voltage. This is why fully charged up Ryobi batteries can be over 20v even though they are 18v tools. 

Model:LGDAHB21865 (ICR18650HB2)
Capacity:1500mAh Rated
Voltage:3.65V Nominal
Charging:4.20V Maximum
750mA Standard
4000mA Maximum
Discharging:2.50V Cutoff
300mA Standard
30000mA Maximum
Description:Teal Cell Wrapper
White Insulator Ring
18650 Form Factor


It is possible if your Ryobi battery is defective to repair it. If you follow the steps mentioned in this article 99% of the time you can get your battery charging again.

I have repaired a neighbors battery after he dropped it from about 8m off a roof. An internal charge lead solder joint had failed. After 5 minutes of tearing apart the battery and resoldering the joint, his battery would charge up again.

The above tips also work for the 36v range of batteries but you will have to separate each bank of 12v to jump-start them.

By design lithium-ion batteries slowly degrade. After around 500 charge cycles you may have 80% total capacity of the original battery. Excessive heat and temperatures below 10 deg celsius will degrade batteries faster.

Replacing the internal battery cells with new 18650 lithium cells can return your battery to 100% capacity. With the cost of cheap Ryobi knock-offs, it may be worth your time to just buy the Ryobi 18v aftermarket batteries.

I love these cordless tools. They are a great addition to the DIY toolbox and every man should have these tools in their garage.

Let me know in the comments below if you have any other tips and tricks to revive old Ryobi batteries.

Disclaimer: It is very possible on any DIY project to damage your property, void your property insurance, create a hazardous condition, or harm or even kill yourself or others. This website will not be held responsible for any injury due to the misuse or misunderstanding of any DIY project. You can also void your warranty by opening products up or tampering with them in any way.

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  1. No, once you get the battery charged it should charge and recharge no problem again. Just don’t run it completely flat. It should recharge up fine.
    If it discharges by itself you may have an internal short.

  2. If you continuously just charge until green light comes on for charger then immediately remove from charger, or partially charge, the five cells do not have a chance to fully balance their state of charge. This is common for work environment where you are continuously recharge and swap battery packs.

    Once they get out of balance you will have less capacity as the internal control electronics shuts pack down when lowest state of charge cell runs out when in use. When charging it will terminate charge when highest state of charge cell reaches 4.2v leaving other cell partially charged.

    If you leave battery pack in charger for several hours, after green light comes on, the cells will have a chance to balance.

  3. Lucky to find your DIY. Left (2) p107’s flat all winter. Now defective. I guess we can’t just go to the + and – on the charging pole to accomplish the same thing. Never has this problem with my very old CRAFTMAN or BLACK AND DECKER BATTERIES. Hope to hear from you soon
    Thanks again,
    Tom C.

  4. What do you recommend for over winter of batteries? Charge once a month, leave on charger, let them go dormant and do your fixing spring???

    Tom C.

    • Hey
      I read your article and it is very helpfull for me.I would be very grateful if you could pay attention to my problem. I have a Ryobi 18v battery pack and charger. But it won’t charge. After connecting the battery to the charger, after the red LED blinks, the green LED stays on and the battery will not charge. The battery is a new battery and I have two battries. Both have the same result. Battery voltage reading is 11.6V


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