The other day, I hooked up my Battery Tender to charge my battery to an optimal level as I didn’t use this battery a lot but instead of the solid red light I got a flashing red light at me.
At first, I thought the charger was bad but when I tested it with another battery it worked perfectly fine.
But as soon as I tested the battery using a multimeter I got to understand the real reason and it was clear as to why my Battery Tender refused to charge it.
I also have a video about this topic which I uploaded on YouTube and you can also watch it below.
I was able to fix this issue by jumpstarting the battery which was already below 3V. Then I tried charging it again and this time it worked fine.
How To Fix Battery Tender Red Light Flashing or Yellow
Here is how to fix the issue and get your battery to charge again.
Battery Tenders are smart chargers used to keep the voltage of a battery to an optimal level so that it doesn’t deplete itself too much, especially the lead acid battery that can lose its charge if not being used.
The reason that I was being shown a flashing red light was due to the battery being below 3V.
This battery was not in use for more than 8 months and lost all of its charge, and using a multimeter it revealed a voltage of just 1.08V on my 12V battery.
The Battery Tender can only charge the battery if it is above 3V otherwise it will flash you with the flashing red or sometimes yellow light.
I decided to jump start my 12V battery using a car battery which is also rated at a capacity of 12V.
I carefully connected the two batteries using jumper wires and connected the terminals of the two batteries together, remembering positive to positive and negative to negative.
You can see the markings of the terminals on the top of the cover of the battery so make sure to not mix them up.
Related: What I Did When My Battery Tender Flashing Red and Green
After leaving the two batteries connected for at least 15 seconds, I checked the voltage of my dead battery again only to find out it was now holding 6.8V which was more than enough for the Battery Tender to charge it again.
I plugged in my Tender and connected its prongs to the battery to finally see a solid red light which meant it was charging again.
The problem was finally fixed and the let the Battery Tender do its job. If jump charging doesn’t help putting some juice in your dead battery, replacing the battery with a new one can help you fix the issue.
