I bought a Motomaster car battery pack es5000 2 yrs ago. After 1yr the charge light does not light up when I plug it in for charging and it doesn't charge as the charge in the pack remains the same. I have the ESA217 charger that came with it. The pack has a charge and I have used it since but cannot charge it. Could the charger be faulty? It used to work. I am not sure if I should spend the money to buy a new charger.