Check the batteries with a amp meter not plugged in to the charger. After plugging in the charger see if the read 5 or 10 amps higher depending on the charger. If all batteries read 5 or 10 amps higher the charger is fine. Batteries sometimes new ones will be bad. I didn't figure this out Nic did when I was having issues with my cranking battery. I can get Exide batteries for 68 bucks through Nics work if you need one. 31 series if I remember correctly.