Sony CP-A2L USB Portable Power Supply

Looks like Sony's getting into the business of (portable, rechargeable, Li-ion battery packs). Reasons I got one:

• iPhone battery life seems to be shortening. Using it for a whole day out leaves uncomfortably little battery
• Might have to charge other iPhones
• Along with an iPad
• Useful on holiday

Reasons I got this specific one:

• 2 USB ports
• Cheap (it was on offer)

Tech specs:
Capacity: 3.6V, 4000 mAh = 14.4 Wh (yes, I know voltage isn't constant so this is an overestimate)
Charging time: 5 hours
Weight: 44.5g (meaasured, AC adapter, stated 45g). 146.7g (measured, battery pack, stated 145g)

Hardware

 When you first open the box, this is what you see. The top box contains the manuals and power cable.

First - what's the top white box? That's the AC adapter. It's 100-240V to 4.1V. I'm not sure how this design is better, except it doesn't use proprietary cables.

Charging

• 5 hours is a bit long to charge
• AC adapter got worryingly hot at first, then cooled off. I think it charges faster when there's less power remaining, so the adapter gets hotter.
• Adapter also makes a sound during charging
• Cannot use USB ports while charging! It would have been nice for this to double as an AC-USB adapter as well. I guess they don't want to encourage people to leave this charging (the instructions say to turn off the power when full)

• The connection on the battery pack is on a circuit board. It's hidden behind the green door. I'm worried something may touch the contacts and short the battery.
• Hey, what about using USB connectors to charge? That way, the adapter can double as a USB power supply.

Use

• Can charge iPad and iPhone at the same time! Yes, it has the intelligence to charge the iPad.
• Turns off automatically if you unplug the device. Supposed to turn off if the device is full as well (untested) 
• Reminder: iPhone 4 battery capacity = 5.25 WH, iPad 2 = 25 WH, so this should be able to charge 2 iPhone 4, but can't fully charge an iPad 2

Indicator light
This is my hierarchy of indicator lights, from best to worst:

1. Shows amount charged when charging and time left to charge. Indicates (not shuts off) when full. (MacBook)
2. Shows amount charged when charging. Indicates when full. (iOS devices, Kensington battery pack)
3. Shows amount charged when charging. Shuts off indicator when full.
4. Shows when charging (not amount). Indicates when full. (Kindle, Oral-B toothbrush, Nikon D50 charger)
5. Shows when charging. Shuts off when full.
6. ???

The CP-A2L is at 5, which is the bare minimum of charging indicators.

Compared to Energizer XP4001

The Energizer XP4001 is the most suitable to compare this product with, since both are 4000 mAh and can charge 2 devices at once. In fact, I was considering this before I got the CP-A2L.

• Although both are 4000 mAh, the XP4001 is at 5 V while the CP-A2L is at 3.6 V. This means the XP4001 has 20 Wh, or 139% the capacity of the CP-A2L. You could also say the CP-A2L has 72% the capacity of the XP4001. I wonder if Sony reduced the voltage to increase the mAh, since that's what people compare?
• XP4001 recharge time is 4 hours
• XP4001 is 150 g
• XP4001 output up to 1.5 A
• XP4001 includes tips for a few devices and coiled cables, which should be easier to use on-the-go. The tips are useful since several devices don't come with USB charging cables.
• XP4001 is $80 at the cheapest, CP-A2L half the price at $40.
• XP4001 uses the standard adapter where the bulk is at the plug and there's a thin cable to the device. This might not last as long if the cable frays.
• Both claimed rechargeable for 500 cycles
• XP4001 has 3 year warranty, CP-A2L says it has a warranty but doesn't specify how long
• XP4001 may have more safety mechanisms. At least they both have temperature protection.
• XP4001 may come charged (CP-A2L does not)

Update 7 Jan 12

I was thinking about how I use this, and I think the thing I'll look for in my next battery pack is charging speed. If you're on the go, you may only have a few minutes to charge your batteries. It would be nice to get as much power as you can.

Update 28 Jun 13
After using this for a while, I noticed it doesn't charge devices as fast as other battery packs. I suspect it can only output 0.5 A on each USB port, which is considered low. It also has the double problems of using a proprietary power supply and charging slowly (only 1 A charge current and 4.1 V). I mean, if you're going to charge slowly, at least use a USB supply so I don't have to bring an extra adapter. If you need a special adapter to do what every battery pack does, what's the point? As a result I do not recommend this battery pack.