A while back I [purchased](http://brooksreview.net/2011/08/monoprice/) the [Monoprice](http://www.monoprice.com/products/product.asp?c_id=108&cp_id=10831&cs_id=1083110&p_id=8295&seq=1&format=2) PowerRocks for two reasons: I didn’t own a battery back up for USB powered devices and it was dirt cheap. It works well and packs quite a punch, but because of that it is big and heavy.
I rarely carry it around and so it is usually stashed in my car, only making into my bag when I travel in a plane. With the battery woes on the iPhone 4S I decided that I really needed a small battery backup to carry in my bag, possibly in a jacket pocket.
I finally grabbed one of the reasonably priced, small, [Mophie Juice Pack Reserve](http://d.pr/wPuh).
What surprised me most about the Mophie is just how lightweight it is — it’s lighter feeling than most AA batteries — making it a great in-bag travel companion.
[
](https://f3a98a5aca88d28ed629-2f664c0697d743fb9a738111ab4002bd.ssl.cf1.rackcdn.com/mophie-closed.jpg)
That’s great and I love it for that, but does it work? Kind of.
I ran a few tests using the Mophie every time my battery started to run low (below 40% charge remaining). The only indicator on the Mophie is a single LED (green charged, red close to dead, no light is a dead battery).
In my testing I found that you could expect to increase your battery life by 20 plus the current percentage shown on your remaining battery when you juice the phone off of a fully charge Mophie. So if you had 10% charge left, the Mophie would bump that up to 30%. That’s not earth shattering, but the thing is tiny and weighs nothing — for emergencies that’s not a bad bump.
In one incredibly scientific test I moved my iPhone 4S battery from 14% to 38% in 50 minutes and roughly 30 seconds. The Mophie was completely dead after this and I only sent one text while the iPhone 4S was “charging”. That’s enough that carrying the Mophie is fine for me, but probably less than most would hope for.
I would again remind you that the Mophie really is light weight.
### Is it Worth It?
[
](https://f3a98a5aca88d28ed629-2f664c0697d743fb9a738111ab4002bd.ssl.cf1.rackcdn.com/mophie-usb.jpg)
That’s a question I have been struggling with because there are several factors I need to consider:
1. For this device to be “worth it” I need to always have it on me when I need it. That’s not going to happen in the summer when I am out and about because I don’t have the pocket space to carry this thing. However, in the winter, I bet I would have to be careful not to wash the Mophie because it would be easy to forget it in a jacket pocket. Since I live in Washington State where it is more winter than summer — I’ll say it is worth it for me.
2. How convenient is it? Turns out the built in charging cable for both the Mophie and your iPhone is pretty great. Making it super easy to charge your iPhone with and to recharge the device itself. However, it doesn’t fit securely enough for me to the bottom of the phone and when you set the phone down on the table it props up the end it is plugged into just a few millimeters — that’s not good if you want to hit the home button with the Mophie plugged in.
3. The charge itself is a ok amount and has proven to be enough for the times that I have needed it — but it’s hardly a conference level battery backup solution.
[
](https://f3a98a5aca88d28ed629-2f664c0697d743fb9a738111ab4002bd.ssl.cf1.rackcdn.com/mophie-dock.jpg)
Overall I would say that if near the end of the day you sometimes find yourself needing a boost — or when you know you will be out and about quite a bit, then this device is a pretty useful thing. However if you just need something to carry in your bag and size/weight is no issue — you are better off with something else. Also if you know you are going to for sure need it, one of those silly battery cases is probably a far better bet.
Note: This site makes use of affiliate links, which may earn the site money when you buy using those links.