Once will be sufficient. The 3.4 amps is simply the current you are charging at. Set your charger to the type battery (Ni-MH), cell count (2) and charge rate or current (3.4 amps). The current will begin at 3.4 and drop off as the battery starts nearing capacity. Connect your balancer plug to the charger also and each cell will stay balanced with the other. Hope this helps...RD