If the battery life in the Nexus 5 isn’t quite what you were after then this battery case from i-Blason may be just the thing you’re after.
The case adds a 2,500mAh external battery built into a slim slider designed case, which gives full access to all the ports and also includes a kickstand. The external battery will output 5V/500mA and is equivalent to at least a full charge for the 2,300 mAH battery included inside the Nexus 5. The battery case comes with 4 indicator LEDs which will show the drops in power in 25% increments.
The case is listed on Amazon at US$54.95 but will come up at AUD$64.44 at checkout, with Shipping & handling, estimated at around 10-16 business days for delivery, adding an extra AUD$24.61 to the price, for a total of AUD$89.05. The case also includes a One Year Limited Warranty with i-Blason, head on over to Amazon to check it out.