I bought a Jackery that can charge an iphone 6+ 4 times and it really does. It wasnt expensive either. Here's a link to the one I bought. https://www.amazon.com/gp/product/B00AANQLRI/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
I honestly have had 0 trouble with it. Works like a charm. It has 2 charging ports. 1 charges faster than the other for some reason but I got this one with 2 ports because me and my friend both kill our batteries when we go on pokemon go adventures.
Edit for some extra info: Only downsides are it's a bit heavy and it takes awhile to charge (Usually over night) from empty to full. To solve the weight problem, just get a backpack, a long charge cable and keep it in there while you use your phone. You wont notice it.
buy this. gives 4+ ish charges to a phone, forget waiting around for your phone to charge. best $30 ive ever spent. it's a very well-built model, its my 4th external battery , the first 3 were cheaper but junk. 2 charging ports too, and a little built-in flashlight, it's nice.
I use this one. I like that it is bright orange so it is easier to find on the bus or inside my bag.
I have a silver version of this: http://www.amazon.com/Jackery-Portable-Battery-Charger-External/dp/B00AANQLRI and love it. The color is an exact match to Apple's iMac/Mac mini lineup so it blends in well sitting on a desk. It's a little heavy but in return you get a very solid charging brick. I keep it in my backpack with a lightning cable. I have used it with my Watch and iPad at the same time, Watch charged just as fast as it would in a wall socket. And it has a bright flashlight attachment, which is nice.
But if you want to only charge your Watch, just get a smaller one that slips into your pocket. Those would still charge the watch 10-15 times. The one I linked would charge it over 50 times.
Just another recommendation... Jackery
I have no experience with the Anker, but I have a Jackery. Just another option. It's only 10400mah though.
The Jackery brand lipo battery packs allow usage in the 'ups' mode you describe - where you concurrently charge and can independently have full current (independent of the input) to the outputs. In particular, this one does : https://www.amazon.com/gp/product/B00AANQLRI/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
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I was planning on using this. https://www.amazon.com/Jackery-Premium-Portable-External-Panasonic/dp/B00AANQLRI
This is for a custom tablet.
You should also get a portable battery charger. I bought one of these awhile ago and it's really great
I just got back from a two week trip to the UK & Ireland, with lots of camera crap to keep charged. I travel with two of these CubeTaps matched with the appropriate US to UK adaptor.
All of my Apple stuff (phone, MBP etc.) adaptors can handle 220, and my panasonic, canon and wasabi chargers can too. I also take two Jackery Battery supplies which I charge every night and use during the day to keep topped up... they are lifesavers for traveling.
I used these two. I loved the Tylt case. I think they make cases for all the major phone brands now. Having the giant backup battery was nice too, especially the day that my charging cable broke and i didnt charge my phone at night.
Actually the screen with the G4 is a special LCD that turns off certain regions when not used saving an additional 20% so they say. I think though it is going to have the same battery life as the G3 though. A full charge and constant use the phone lasts a day.
These are the differences between the two cores. So perhaps there is some power savings over the 810. But the G3 has the 805 in most instances, which is a quad core. So any savings from the screen would go for the additional cores i.e. I really think we have a wash power wise and if there are any savings, I do not think they would be noticeable over the G3. The average talk time for the G4 is rated at 20 hours. For the G2 it's 16 hours. For the G3 it's 16 hours too. But if your on the internet aka reddit alot, those numbers can be optimistic anyway. Also, lollipop 5.0 does manages the battery better giving some increase in life. But I notice that I get consistently a day of use with it usually.
The answer for me is more chargers and battery packs everywhere. So it's not a big deal for me presently.
If I had your phone, and the battery life was slipping, I'd make sure that I was using an OEM charger, and I would install a new battery in it, to bring it up to specs. And wait for the next iteration from LG whatever that was - depending on what your particular carrier cell phone plan offered.
I think the next logical upgrade for me is the "LG note." LG is working on their own optimized core to get away from the snapdragons. It supposedly will increase battery life also a bit. Also, if they put a slightly bigger battery in the phone, then it would be competitive with anything out there usage wise. And with the new camera, the "LG note" could be a very good if not excellent phone.
That's just my opinion on it anyway.