Its wierd but I had the same problem too. I purchased some Intergy 4200 7 cell batteries for my E-Maxx and put them on the Twin Pulse charger. According the the charger they were ready to use but when I used them they gave me about 5-10 minutes of run time. Charged them again and same result. It was suggested that I discharge my batteries. After using the discharger, I recharged them (took about 1 1/2) and they gave me about 30-40 minutes of run time. Every now and then it happens. So my suggestion is to try the same thing. Hope that helps.