In this paper, the end-to-end bit error performance of a dual-hop (DH) energy harvesting (EH) amplify-and-forward/decode-and-forward (AF/DF) system is investigated. In this system, the source communicates with the destination over an intermediate relay when the direct link between the source and the destination is in deep fade. The channels are assumed to be exposed to Nakagami-m fading and all nodes are equipped with one antenna. The relay uses power splitting (PS) and time switching (TS) relaying protocols to harvest energy and uses it to forward the decoded signal or to transmit the amplified version of the received signal to the destination. The bit error probabilities of the considered DH-AF and DH-DF systems are analytically derived for both EH protocols and their performances are comparatively evaluated. Moreover, a system optimization is performed to maximize the bit error rate (BER) performance. For the TS mode, a list of mixture of modulations is provided for different spectral efficiency values and different time allocation parameters. Our comprehensive results on the BER performance of AF- and DF-aided DH networks with EH in the relay, provide basic guidelines for the design of the future DH-EH systems.