I have a Dual Pro 4 bank charger. I just bought 3 brand new group 31 batteries. I used them once, charged them and the were ok. The second time I used them, I tried to recharge them. My charger has 5 lights, showing stages of charge. After a few hours, it was still on one red light, indicating minimal charge. Then, the charger went to 2 blinking red lights on all 3 banks. This, according to my research, indicated the charger overheated and this is a safety cut off. I unplugged it, let it cool, and same result. The cranking battery charged ok. No way all three batteries are bad. Thoughts, and thanks.