Review: RAVPower 10400mAh Power Bank

It is one of my biggest complaints that Apple-Envy in the gadget world has made products with replaceable batteries almost a thing of the past. For phones, I've managed to only buy phones that let you replace the battery, but for tablets, the PS Vita and even the Microsoft Surface, that's simply not been possible.

Our Nexus 10 and Nexus 7 tablets have been in use for over a year now, and the battery life is definitely not what they were when they were new. As a result, when there was a sale on the RAVPower 10400mAh external battery, I bought one at $25.50. You have to be realistic about external batteries. There's power conversion inefficiency between the battery's internal voltage to supply the external 5V available to the USB slot. Most chargers are not better than about 80% efficiency, and this is not the fault of the battery manufacturer. Similarly, you also can't expect to squeeze all the power out of an external battery since once the voltage at the output drops below the voltage of the battery of the target device, no charging can happen. So if your device says it's at 10400mAh, realistically you're not going to get more than 7-8000mAh out of it.

The device is about the size of a pack of cards. It's much smaller than a Nexus 7 or Nexus 10, but is much thicker than my Nokia 521 or Galaxy Nexus. I wouldn't call this a pocketable device, but it's definitely not a hassle to bring it on a long plane flight, for instance. It has 2 USB A slots and a micro USB b slot for charging. It comes with a carrying pouch with 2 micro USB to USB A cables. These cables are coiled, so you can't confuse them with data-capable cables (they are power only), and they're useful because you can stretch them without breaking them. Their inclusion is a nice touch on a budget device.

The Nexus 10 has a 9000mAh battery. Sure enough, from a fully drained device, I drained the RAVPower and only got the Nexus 10 to about 75% charged. The Nexus 10 stayed in use during part of the charging period, so this is about what I would expect. What is impressive about the RAVPower is that I tested it with the PS Vita and the charger worked. This was a surprise because the Vita requires a high charging current as well as specific pins shorted out on the charger and as a result does not work with all external batteries.

The USB slots on my sample were mislabeled. The 1A slot was labeled as 2A, and vice-versa. If you do get one you should check both slots to see if that's what happened with your sample. This is no big deal since once you learn that, you learn which device to plug into which slot.

The battery takes a long time to charge (via a micro-USB input) if you've drained it completely. I estimate the charge time at 12 hours, though my experience with these types of battery is that it charges rapidly to about 80% and then trickle charges to get the last 20%. While charging, the battery does not serve power to the USB slots, which is a pity, since I can see scenarios under which it would be useful to charge this device and 2 others at the same time from one USB slot. Adding that feature would have both increased the price as well as make the battery take even longer to charge, so I can understand leaving it out.

Batteries are essentially consumable devices, with most batteries lasting no more than 300 charge cycles or so (less if they're frequently fully discharged and recharged, or stored some place warm). As a result, you should delay buying one for as long as you can. However, if you have an old tablet, buying one of these battery packs is much cheaper than buying a new tablet or the time cost of replacing the (difficult to extract) battery yourself. If that's your scenario, then I can recommend the RAVPower external battery pack. They come on sale rather frequently, so I'd advise setting an alert on camelcamelcamel or Slickdeals.