ARCADIA iMILCH ACD66 External Battery Pack Review

We bought this device (from Amazon) following a visit to the Goodwood Festival of Speed. We started with a fully charged iPhone 4 which was being used to provide a pretty much constant stream of updates to Facebook and Twitter (with location), over a very poor 3G network. This resulted in the battery lasting little more than four hours. This led us to look at ways of extending iPhone 4 battery life, when there are no mains power sockets to hand. When we bought our ACD66 device there was a special offer on if you left a review on the Amazon website.

On a sunny day, you could just use a decent sized solar cell to charge the battery and this also resulted in a new project to build a solar USB charger. This assumes that you are outside and that the sun is out though.

To cover those situations where this is not the case, we decided to purchase this device. We bought it because it could also be recharged using our solar charger or via many other methods. It has two USB output ports for charging your devices and one of the ports can supply the 2.1A required to recharge an iPad 2. The battery capacity is rated as 6,600mAh. Basically, it can charge up pretty much anything that can be charged via a USB port.

In The Box

The box
The ACD66 is supplied in a hard, plastic case and with a protective sheet stuck to the top, shiny surface. The bottom is a softer, non-slip finish which is a nice touch.

In the box
The box includes the ACD66, a brief instruction leaflet, a coiled cable, and a couple of adaptors. The supplied cable combines with the two adaptors to give you either a USB type-A to micro USB, or USB type-A to mini USB cable.

USB Ports

USB port types
It is worth recapping on the types of USB ports at this point, to make sure things connect together as planned. The outputs are standard USB type-A ports but have special resistors connected to them, to signal how much power they can deliver. This power can only be delivered though, if the connected device understands what the resistors mean. The iPhone and iPad recognise very specific configurations. The ACD66 is charged via a mini-A USB port and these are still common on portable disc drives and some phones.

The ACD66 has two USB outlets rated at 1A and 2.1A. Although it is not mentioned in the instructions, the packaging mentions its 3.1A output, implying that both outlets may also be used in parallel.

In Use

We weighed the device at exactly 200g and it is 87mm × 112mm × 15mm deep. This makes it quite portable and it would not be a problem carrying it around with you in a bag or rucksack to events or using out in the field.

The device was shipped with two of the four blue LEDs lit. We plugged it into a laptop (on mains power) USB port at 12:50 and the third LED started flashing. At 14:15 (25 minutes later) the third LED stayed lit and the fourth started flashing. At 17:09 (4 hours and 19 minutes in total) all the lights where solidly lit, which means the device is fully charged. Throughout the charging process, the device stayed cool to the touch. I don't know what current the laptop USB port was supplying but, I'm guessing it was 500mA.

If you press the power button briefly the LEDs indicate the state of charge for ~5 seconds and then the device turns itself off again. It also automatically turns itself off after 60 seconds, unless it detects a device is connected. A single flashing LED indicates <20% charge, a single solid LED indicates 20-40% charge, 2 solid LEDs indicate 40-60% charge, 3 solid LEDs indicate 60-80% charge and 4 solid LEDs indicate 80-100% charge.

iPad 2

We are still using and testing this device with iPhones, iPads, etc. This section will be updated very soon.

iPhone 4

The ACD66 supports fast charging of the iPhone 4. Our initial test showed the following results. At 11:41 we started charging with the iPhone at 74% and using the 1A output port. At 11:45 it was 78%, 12:02 90%, 12:15 97% and when we checked again at 12:21 it was 100% charged. We will do a timed test from completely flat soon.

How Long On Battery Power?

We are currently running an experiment to see just how long we can run our iPhone 4 on battery power alone:

Monday 11th July - Started with a fully charged iPhone and by 21:34 it was down to 3%.

We then charged it again using the ACD66 1A USB port. The charging cycle looked something like this: 21:34 = 3%, 21:37 = 7%, 21:46 = 17%, 22:17 = 52%, 23:09 = 91%, 23:19 = 94% and 23:24 = 95%. It took about 2 hours to reach full charge from almost completely flat. All four lights were still lit on the ACD66, indicating >80% charge still remaining and implying you can charge the iPhone 4 at least 4 times from a fully charged ACD66.

Tuesday 12th July - At 07:34 our iPhone 4 was still at 96% charge and this dropped as it was used: 08:49 = 90%, 09:33 = 79% (heavy use on the train), 12:33 67%, 16:03 = 31%, 19:21 = 15% and 20:24 = 12%.

We then charged it again using the ACD66 2.1A USB port. The charging cycle looked something like this: 21:30 = 5%, 21:39 = 15%, 22:15 = 55%, 23:06 = 91 and 23:16 = 93%. From this we are implying that the iPhone doesn't charge any faster using the 2.1A USB port. As the charged ticked over to 93% the ACD66 lights changed from four to three, indicating 80% charge remaining.

Wednesday 13th July - Was a day off, so iPhone usage was lower than normal. Started in the morning at 08:45 = 87%, 12:32 = 65%, 16:31 = 58%, 17:05 = 52% and 23:23 = 40%. It is very rare that we make it through the day without having to charge it. Never would we normally get on a train to go to work in London with the charge this low either, but the ACD66 has freed us from 'range anxiety'.

Thursday 14th July - At 06:16 = 35%, 08:01 = 16% and 08:58 = 8%. We had to demo some apps so started charging at this point: 09:37 = 51% and 10:27 = 94%. There are still 3 lights lit on the ACD66. At 15:23 = 85%, 19:40 = 64%, 23:17 = 47%.

Friday 15th July - At 06:35 = 46%, 08:26 = 37%, 09:16 = 32% (on train to London), 14:04 = 16%, 17:02 = 6% and 17:19 = 3%. At this point I started to charge the device and noticed that at 18:08 the iPhone was up to 53% but, the ACD66 was completely flat.

This means that the indicator lights are far from linear and the capacity is lower than indicated. On the plyus side it did recharge our iPhone nearly 3 times.


This is a good looking bit of kit and very much complimentary to a black iPhone 4. The ports on the device make it very flexible and we have charged it from a PC, laptop and our solar USB charger. It has a high capacity and can hold a charge for a long time. It is also a nice size and weight.


April 2012

This device is still going strong and has proved itself to be amazingly useful on long-haul flights and holidays. We recently spent two weeks in Mexico and it kept iPhones, iPods and a Kindle going whilst we were on the beach and away on day-trips.

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