Battery Charger Flashing Red Light – What to Do?

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It’s typical for the rear batteries to get warmer than other available banks. The two batteries tend to become warmer compared to other chemistries because of heat produced by the charger’s converter circuitry. This doesn’t imply that the batteries overcharged or charged faster compared to others.

This is normal and the charger will show different flashing lights, each portraying a specific meaning. The inbuilt converter circuitry plays a vital role in determining the flashing light based on the status of the battery. For this reason, this article will try to educate you on the meaning of the flashing red light on the battery charger.

Table of Contents

Why am I seeing the flashing red light on my battery charger?

Restoring bad batteries is what I can begin by as the meaning of blinking red light in my battery charger. This happens occasionally, whereby the charger displays a flashing red light that indicates bad batteries. Experts recommend various methods of restoring batteries that won’t be charged using a battery charger.

In case you insert the battery and you see the red light blinks at an interval of 5 seconds, the voltage of the battery is too high. It is a clear indication that your chemistry requires a restoration, or else, it can’t be charged. So, if you see such an indicator, just know that the battery might be full or bad.

Sometimes the battery might be having a full charge, but still, need charging. In such a case, you are supposed to ensure the batteries are completely drained before trying to charge again. Draining the battery is one way of restoring ‘bad batteries’ and is the simplest way.

Battery Charger Flashing

On the other hand, you will start to see a flashing red light at an interval of 90 seconds immediately after connecting the charger. This issue happens mostly when the battery is over drained, leaving it with no volts. Therefore in such situations, it’s advisable to allow the chemistry to stay on charging for a few minutes.

You don’t have to worry about this 90-second flashing red light because it simply implies that the voltage of the battery is too low. Leaving it on the charging will help strengthen the cells, respond to charging and pick normal operations. I would advise you to leave the batter overnight on the charger while the red light continues to flash.  Detach the battery and give it another try to see whether it picked or responded to charging.

You will continue to see the red light even after unplugging the charger. If it’s irritating, you are required to detach at least a single battery to let the light go off.

The battery charger CHARGE light blinks when charging your battery pack

There are several reasons that may force the charge light display differently. Some of these reasons include:

The surrounding is too icy to charge your battery pack. If you are operating in winter or any cold environment, the battery charger light will blink red. You can change such a situation because of its nature, but you can place your battery on a stand that’s either one or two feet above the ground.

The battery pack hasn’t been in service for a long period. Of course, you will start to see a red light flashing immediately when you insert a battery on your battery pack that has been dormant for a while. Handling such a situation is simple as you only have to expose the pack to the electricity for some hours before reinstalling the battery for charging. It is as simple as that.

Another reason that you are seeing a flashlight on your battery charger is that the connection between the charger and the battery is very poor. Try to check if the wires are not correctly fixed and put them in place.

You should also want to ensure that the battery terminals are in good working condition, free from acid accumulation. I would advise you to rotate the terminal clips or wires, rubbing them on the terminals to ensure they are tightly held in place.

Therefore, if you connect the AC power cord to the outlet and in case the ring terminals or alligator clips aren’t plugged into the battery, probably the green and red lights will be seen. More so, in case you connect the ring terminals or alligator clips together, the art will lack an electrical spark.

Furthermore, the green and red lights will blink alternately when you hook the charger backward. The suitable solution to curb this issue is by connecting the ring terminals or alligator clips to your battery with proper polarity.

In short, connect the Red wire to the positive terminal and the black wire to the negative battery terminal before initiating the charging process. The red light on steady means that the charger is correctly connected to the battery and charging is initiated. Once the battery is fully charged, the light will go off; only if you disconnect the battery.

The battery pack itself might be problematic. Here is another reason that you might be seeing red flashing lights on your battery charger. Try fixing the problem before returning the battery again.

Frequently asked questions (FAQ)

Why is my battery charger flashing green and red?

The green and red lights sometimes alternate to imply that the battery is bad or the 72-hours safety Timer is activated. Besides, it may imply that a good, very large chemistry isn’t charged completely. Or that relatively smaller chemistry is defective.

How should I notice that my battery tender is faulty?

Turning on the vehicle’s headlights to check for voltage is the best way out. In case there’s a 12.7 voltage reading, just know that the battery is completely charged. Otherwise, anything under 12V reading like 11.5V implies you have a faulty battery.


You need to understand that the LED light at the 12DC power input blinks solid red while charging and green when completely charged. Hopefully, you have seen the various meanings of the flashing red light and the popular one is the restoring ‘bad batteries’. It also implies that the battery can’t be charged because it’s full or it’s the temperature is too cold.

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