I have been charging phones and iPads for years, often with off brand devices, but usually with Apple supplied chargers. I have also tried many portable battery devices that will re-charge my phone at ball games, and such. Some are small, some are large. All seem to work well.
Yesterday I read about these two devices in a Popular Mechanics technology review (and recommendation). Anker is a well know, and highly praised, company that makes charging devices and portable back-up batteries. What I did not know until this article that Anker was founded by Google alumni. That says a great deal right there. So, I looked up these devices on Amazon (links below). Both are worth a look. The 4 port device was highly praised by Popular Mechanics (high power, many safety features, faster charging than most chargers as well). But my real discovery was the $9 car-charger. I loved the description of it. And have ordered one to test it. It is fast, redesigned to be smaller, can be left plugged in when there is no device attached, it is smart enough to turn itself off if no device is plugged in. The pilot light changes color when you insert a device. That lets you know it is charging. It will not over-charge your device. And other features as well. I have two car chargers already, but they lack some or all of these features. Take a look. My phones are too costly to risk as less that perfect car charger. Comment if you like.