Default Not charging while using lots of power?

I recently got this phone and also got the new 4.8A Anker charger with built in cable + USB port.

I noticed that my phone won't charge in the car while it's being used as GPS. It won't discharge (at most very slowly) but it stops charging after a few minutes.

I found my sister's nexus 4 does the same thing!?

So I called anker and told them about it and they thought maybe I had a faulty unit, so I got the replacement and it's doing the same thing.

I wondered if it was a LG issue (since the OG and N4 are siblings) and checked if I could duplicate the effect on my home charger (which, BTW, can allow up to 1.8A to be pulled) and I was able to.

I would prefer my phone to actually gain battery life while using it as GPS. Lol. Is there a way to stop the phone from just living off the charger and not actually charging?

Thanks.

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