Reducing power consumption and increasing battery life of sensor nodes are important challenges for sensor networks. In this paper, we propose a simple routing protocol that constructs routes depending on a remaining battery capacity. Then, we explore a new type of sensor network with forwarder nodes and a data aggregation scheme. The forwarder node is a special node that has a large size of battery and supports the route construction to the sink node from sensor nodes. Finally, we evaluate the advantage of the data aggregation scheme for this sensor network. In numerical results, we show that our protocol can extend the lifetime of the sensor networks and improve the event delivery ratio at the sink node.