Ryobi Dual Charger Not Charging Both Batteries? Fix It

Updated 14 November 2026 · Standard formula, shown below

If your Ryobi dual charger is only charging one battery and ignoring the other, the fix is usually a simple reset, a port cleaning, or a battery contact issue—not a dead charger. This article walks you through the most common causes and the step-by-step fixes that resolve the problem in the majority of cases, so you can get back to work without buying a new charger.

How a Ryobi Dual Charger Works

Ryobi’s dual-port chargers (such as the P118B and P118C) charge two batteries simultaneously by splitting the charger’s total output between the two ports. They do not charge both batteries at full speed at the same time; instead, they distribute power based on each battery’s state of charge and temperature. The charger communicates with each battery pack through the small terminals on the battery—not just the large power contacts—to determine when to start, pause, or finish charging. This communication is why a dirty or bent signal pin can cause one port to appear dead even though the other works fine.

First Steps: Quick Checks Before You Dismantle Anything

Unplug the charger for 30 seconds, then plug it back in. This resets the charger’s internal logic and often clears a stuck fault condition.
Swap the batteries between ports. If the same port fails with both batteries, the problem is the charger. If the same battery fails in both ports, the problem is the battery.
Check the outlet. Plug the charger into a different wall socket, ideally one you know works. Some dual chargers draw enough current to trip a GFCI or a weak circuit.
Inspect the battery contacts. Look for dirt, grease, or corrosion on both the battery and the charger terminals. Clean them with a dry cloth or a pencil eraser—do not use water or solvents.

Clean the Battery and Charger Contacts

Dirty contacts are the most common reason a dual charger ignores one battery. The charger relies on the small signal pins (the thin metal strips between the large power terminals) to read the battery’s temperature and voltage. If those pins are covered in grime or bent, the charger may not even recognize that a battery is inserted.

Use a dry, lint-free cloth or a soft pencil eraser to gently rub the metal contacts on both the battery and the charger port.
If you see any dark spots or pitting, use a small amount of isopropyl alcohol on a cotton swab to clean them, then let everything dry completely.
Check that the small pins are straight and not pushed down. If one is bent, you can carefully straighten it with a toothpick or a small flathead screwdriver—but be gentle; they break easily.

Check the Battery Itself

Sometimes the battery is the problem, not the charger. A battery that has been fully drained and left sitting for months may enter a “sleep” mode where the charger doesn’t recognize it. Here’s what to try:

Try a different charger. If a single-port charger works, the battery is fine and the dual charger is at fault.
Check the voltage. If you have a multimeter, measure the battery’s main terminals. A fully charged 18V battery reads about 20V; if it reads below 10V, the battery’s protection circuit may have shut it down.
Jump-start a dead battery (carefully). Some users revive a deeply discharged battery by briefly connecting it to a known-good battery in parallel for a few seconds—positive to positive, negative to negative. This is a temporary fix and not officially recommended, but it works for some. If you try it, do it outdoors, away from flammable materials, and only for a few seconds.

Common Problems and Their Fixes

Here are the typical issues you’ll encounter and what to do about each:

One port never lights up: Likely a dirty or bent signal pin. Clean and straighten the pins, then try again.
Both ports light up but only one charges: This is normal behavior for some dual chargers—they alternate or prioritize. Wait a few minutes; the second battery should start charging once the first is topped off.
Battery gets hot and charger stops: The charger has thermal protection. Let the battery cool to room temperature before retrying.
Charger makes a clicking sound: Could be a faulty relay or a shorted battery. Stop using it and test with a known-good battery.
Charger works but only with one specific battery: That battery may have a damaged thermistor (temperature sensor), causing the charger to reject it. Try that battery in a different charger to confirm.

When to Replace the Charger

If you’ve cleaned the contacts, reset the charger, and tried multiple batteries, and one port still doesn’t work, the charger’s internal circuitry for that port is likely faulty. This can happen from a power surge, a drop, or just age. Before you buy a new one, consider:

Warranty: Ryobi chargers typically come with a 3-year warranty. Check your purchase date and contact Ryobi support if it’s still covered.
Cost of repair vs. replacement: Dual chargers are relatively inexpensive, and repair shops rarely fix them. Replacement is usually the practical choice.
Compatibility: Make sure any replacement charger is compatible with your battery voltage (18V, 40V, etc.) and chemistry (NiCd, NiMH, or lithium).

Alternatives to a Dual Charger

If your dual charger is beyond repair and you need to charge multiple batteries, you have a few options:

Buy a single-port charger for each battery. This is cheaper upfront but requires more outlets.
Use a multi-bay charger (like a 4-port model). These charge batteries sequentially, but you can leave them all in overnight.
Consider a rapid charger. It charges one battery much faster, so you can rotate batteries more quickly.

Frequently Asked Questions

Why is my Ryobi dual charger only charging one battery at a time?

This is normal for most dual chargers. They share a single power supply and can only charge one battery at full speed. The charger may switch between ports automatically, so one battery might pause while the other finishes. If neither battery ever charges, then there’s a problem.

Can I charge a Ryobi 18V battery on a 40V charger?

No. The voltage and connector are different. Using the wrong charger can damage the battery or start a fire. Always match the charger to the battery’s voltage and chemistry.

How do I reset my Ryobi charger?

Unplug the charger from the wall, wait 30 seconds, and plug it back in. This clears most minor faults. Some models also have a reset button—check the manual if you have one.

Why does my battery charge but then dies quickly?

That’s usually a battery issue, not a charger issue. The battery’s cells may be worn out or have high internal resistance. Try a known-good battery in the same port to confirm the charger is fine.

Is it safe to leave batteries on the charger overnight?

Ryobi chargers have overcharge protection, so leaving a battery on overnight is generally safe. However, it’s good practice to unplug once fully charged to reduce stress on the battery and save energy.

Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.