Does my battery seriously have a problem or do I have a virus? This notification keeps popping up on my phone and I don't know if it's real or not, it reads:

"Battery has been infected by 6 serious problem! Install DU Battery and all problems will be wiped out."
It's a virus/maleware.

Sources that describe very similar situations:

http://forums.androidcentral.com/ask-question/658156-apus-du-battery-saver-virus.html

https://productforums.google.com/forum/#!topic/nexus/7XbiK-frhVA

It sounds like it's actually a really old scam (this may be a newer variant of it)  Here's a story from 2011 that sounds like the same issue:

http://www.pcworld.com/article/241967/sleazy_ads_on_android_devices_push_bogus_battery_upgrade_warnings.html