I have a 8.4v 3000mah that came with both my rustler and stampede 4x4. I am using a Hitec x4 charger to charge both of them at the same time. I use a charge rate of 4amps, a capacity cutoff of 3000mah, and the default delta peak sensitivity setting (which is 7mv). I used in the past, a traxxas ez-peak charger, which worked great but took forever to get both my batteries charged. When I first charged these batteries with the Hitec x4, the first battery stopped and the charger said it was full (it got up to about 2700mah). The second battery stopped because it reached the 3000mah capacity cutoff. I didn't think the second one was fully charged because it wasn't even warm when it was done, so I gave it a few minuets and plugged it into my ez-peak charger and it ran for another 15 or so mins (before it got warm and shut off). After doing this I decided to see if the first one got completely charged, so I did the same thing, I plugged it into the ez-peak charger and it ran for 10 mins before shutting off. How can I make the Hitec charger completely charge both my batteries? Do I need to increase the delta peak sensitivity? Should I raise the capacity cutoff to 3300mah? Anything input would really be appreciated. Thanks.