Once you have selected the right battery you can check out if I have any recycled Nexus 7 1st Generation batteries on eBay
Below is a link to the current recycled Nexus 7 Spare Parts I have available on eBay.
Once you have the replacement battery the video below shows you a simple and slow step by step guide as to how I safely shutdown my Google Nexus 7 Wifi + 3G model.
It then shows how I safely crack open the back of the case, disconnect then remove the internal 3G Lithium Battery ensure I have the right battery then how I install a new battery, close the back and restart the nexus 7 3g.
Remember, I always back up my devices before doing anything, please ensure you do the same. I take no responsibility or liability for this fix, It is for educational purposes for competent with sufficient skill and experience to complete this task. If you find this useful please hare it and give it the thumbs up.
fixed1t