Question about portable charger

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http://forums.androidcentral.com – Well, as everyone knows, nexus 4 havent very good battery life. So, I was thinking to carry a portable charger with me.But I don't know whether it suits nexus 4 or not. Look at this product --->Sony CP-ELS Its features says that it takes 6 hours of charging and 500 charging cycle <--- Well, what does this means? Is it means that after full charging, it charges other phones 500 times? Will it safe and supports nexus 4 or not? Tell me any other portable charger or things if u know.. thnx in advance One more thing, I am from India, so, tell me the product which is available (HowTos)