Ampy Move Teardown and Review

[kalleboo]

http://drop-kicker.com/2016/01/ampy-move-teardown-and-review/

Tl;dr: it's crap!

Sarcasm aside, this really is a perplexing result.  I could understand a project where a promising and novel technology is proposed only to find that it’s too difficult to manufacture, or too expensive, or too fragile, or not as effective as originally thought, but the Ampy story is different.  Unless the product underwent some major design overhaul since their campaign and still delivered with few delays, it really looks like this team took a fairly well-understood and poor solution to a problem and pitched it as something extraordinary.

We’ve seen people pitch readymade solutions as new before, but this isn’t that either.  The Ampy team went through the effort to create an entirely new product based on old ideas that have already been shown not to work while adding nothing novel in the process. Given their predilection for Linear parts, I’m a little curious if they just went through a Linear Tech catalog and circled all of the parts that mentioned “energy harvesting battery charger.”

Ampy went to great lengths to never promise concrete results to their backers, so it comes as no surprise that the device performs only to the most generous standards.  I can only imagine how they explained their “proprietary technology” to their investors though and what those investors are going to say when they discover the man behind the curtain trying to squeeze a coil of wire into a smartwatch.

[tom66]

The charging IC is only rated at about 50mA, which means you could, at best, charge your phone with 50mAh of energy.

How much energy does it take to call? My S4 pulls 0.6A @ 5V idling on the home screen with 100% charged battery. Say it takes 60 seconds to boot the phone up & book a cab and power consumption is the same throughout, although in reality if the CPU and radio are in use, the power consumption will be much higher. That would use 7.4mAh @ 3.7V, but "90 seconds of shaking" would only generate 1.25mAh if you could somehow reach the maximum power point of the device.

So their claim that you could make an Uber booking by shaking for 90 seconds is dubious, at best (I smell a rat)

[janekm]

The charging IC is only rated at about 50mA, which means you could, at best, charge your phone with 50mAh of energy.

How much energy does it take to call? My S4 pulls 0.6A @ 5V idling on the home screen with 100% charged battery. Say it takes 60 seconds to boot the phone up & book a cab and power consumption is the same throughout, although in reality if the CPU and radio are in use, the power consumption will be much higher. That would use 7.4mAh @ 3.7V, but "90 seconds of shaking" would only generate 1.25mAh if you could somehow reach the maximum power point of the device.

So their claim that you could make an Uber booking by shaking for 90 seconds is dubious, at best (I smell a rat)

Well... misleading at least. It's entirely possible that the event occurred as they described:
- The ampy was used until fully discharged, battery is cut off by the LTC1540 comparator (with hysteresis!) (battery voltage during discharge load condition would be lower than no-load voltage)
- While not used, the battery chemistry in the Ampy recovered some state of charge, but didn't raise the battery voltage enough to overcome the hysteresis
- shaking the ampy applied a charge voltage at the battery and the LTC1540 which overcame the hysteresis, reconnecting the battery to the boost converter
- enough capacity was left in the battery at this point to charge the phone for the single phone call (phone also will "shut off" before fully discharged to protect battery)

The article was musing about why all the parts are from LT... Easily explained, an LT sales engineer designed the circuit for them

[mikerj]

The charging IC is only rated at about 50mA, which means you could, at best, charge your phone with 50mAh of energy.

How much energy does it take to call? My S4 pulls 0.6A @ 5V idling on the home screen with 100% charged battery. Say it takes 60 seconds to boot the phone up & book a cab and power consumption is the same throughout, although in reality if the CPU and radio are in use, the power consumption will be much higher. That would use 7.4mAh @ 3.7V, but "90 seconds of shaking" would only generate 1.25mAh if you could somehow reach the maximum power point of the device.

So their claim that you could make an Uber booking by shaking for 90 seconds is dubious, at best (I smell a rat)

Unless I'm missing something, I think you have your math backwards.  0.6A @ 5v is 3 watts, and (ignoring conversion losses) would be equivalent to 0.81A @ 3.7v.  0.81A for 60 seconds would be 13.5mAh.