What to do if your car battery charger won’t charge
Here’s why your battery charger won’t charge a dead battery
Some digital battery chargers won’t even start to charge a dead car battery
Because the battery voltage is below minimum specifications
Modern digital battery chargers run a series of tests on the dead battery before they’ll begin a recharging cycle. In most cases, a digital charger won’t charge a dead battery if the battery voltage is at or below 1-volt. This safety feature is designed to protect the charger and battery from damage due to overheating.
In addition to the low voltage test, the charger will also check to see if the battery is accepting the charge. For example, if battery voltage doesn’t rise appropriately during the charging process (indicating a possible internal short), or if the maximum charging time has been exceeded and the battery is still not up to charge, the charger will stop charging and display an error signal.
Three ways to charge a battery when the battery charger won’t charge a battery
Method 1: Override the charger’s safety features
Some chargers allow you to override the error message by pressing the charger button continuously for 5 or more seconds. Refer to the owner’s manual if you see an error message.
Method 2: Trick the charger by connecting the dead battery in parallel to a good battery
In this method, you’ll use jumper cables and connect the dead battery to a good battery in another vehicle. You’ll do this just long enough to get the charger to assume that the battery voltage is high enough to allow charging.
The most effective way to perform this procedure is to disconnect the battery cables on the dead battery before connecting the jumper cables. Then connect the charger clamps, followed by the jumper cable clamps. As soon as all the clamps are attached, start the charger. As soon as it starts charging, remove the jumper cables.
By disconnecting the battery cables from the dead battery, you eliminate the power drain from the vehicle’s computer systems.
Method 3: Start charging with an old non-digital battery charger
Old outdated chargers don’t check for battery voltage before charging; they start right off regardless of battery condition. Use an old battery charger to bring battery voltage high enough so the smart charger can take over and properly recondition the battery.
Use an old non-digital charger to charge the battery enough to the newer digital charger to take over
Rick’s recommendations for the best battery chargers
I’m not a huge fan of the popular NOCO battery 
chargers, but I do like the Clore line of chargers.
The Clore Automotive PL2320 20-Amp, and Clore Automotive PL2310 10-Amp units are some of the best in the business. They charge standard flooded lead acid, AGM and gel cell batteries. Choose from 6-volt or 12-volt and choose the charging rate 2, 6, or 10- amps for the PL2320-10 model, or 2, 10, 20-amps for the PL2320-20 model.
Both models automatically recondition the battery if it needs it.
©, 2023 Rick Muscoplat