How to save large chat history of WhatsApp in Android phone I'm not able to store my WhatsApp chat of single contact in email chat because of large amount of messages so how is it possible?
Your WhatsApp chats are automatically backed up and saved daily to your phone's memory. You can also periodically backup your WhatsApp chats to Google Drive. 
To backup your chats, go toWhatsApp > Menu Button > Settings > Chats> Chat backup > Back Up.
Now, to export a copy of the history of an individual chat or group, use the Email chatfeature instead:

Open the chat for the individual or group.Tap the Menu Button.Tap More.Tap Email chat.Choose whether to Attach Media or not

Note: When sending with media, you can send up to 10,000 latest messages. Without media, you can send 40,000 messages. These constraints are due to maximum email sizes.


Soure: WhatsaApp FAQ