Sometimes it pays to hang around various tertiary institutions. Case in point, when earlier this week, a group was moving out of their old lab into a new one. Events like these are often the impetus for a proper clean-up to be done and with every clean-up comes rubbish just ripe for the salvage. Like a vulture spotting some carrion, I was swooping down on the boxes of unwanted items and picking it apart for the gold inside.
I found two eX-power branded laptop power banks. While the brand is questionable and this style of power bank is rare to see nowadays, in the old days, if you had a laptop without a replaceable battery or the replacements were too expensive, you would use this instead as it was a portable battery that would “act” like the supplied power adapter.
I never owned such a contraption so I thought it would be nice to give them a try. I wonder if they still worked properly after all these years, as they were completely discharged when I got my hands on them. I also found two laptop-style chargers suitable for the units, but not the particular output cables. Oh well, you can’t always win.
The unit is black, glossy and plastic, and about the size of a 3.5″ hard drive. The top side has a push-button LED bar-graph charge indicator, as some older laptop batteries have.
The unit has an easily recognized 5V USB output, with a claimed current rating of 1A. This was the most easiest to test, so we’ll see about this.
The unit does have a claimed 10.8V/3A output which is marked as 9V-12V. I suspect this indicates it’s a switched/fused output from the lithium ion pack directly. As a 3S2P setup, its nominal voltage is 11.1V, but can range from a high of 12.6V down to about 8.4V.
The other output intended for a laptop is claimed to be 19V/3.5A. This suggests the most “beefy” converter inside is providing a regulated output, yet the jack itself is labelled 16-19V. I suspect this means the converter inside may not be quite sufficient to push the full voltage as the pack runs down – it is about 2:1 output voltage vs pack voltage, and thus the current load on the cells can be quite high at full output.
The total capacity is claimed to be 75Wh maximum.
The unit has ribs on the side but is not vented. It gets quite hot while charging, with the lowest unit on the bar-graph lighting red while charging and green when charged. The unit weighs 620g.
The unit isn’t so obvious in how it can be opened. I managed to guess at where the corner screws were …
… but it still would not budge. As it turns out, there are two hidden screws along the edges.
Removing those screws, the unit was still rather uncooperative, requiring some significant force to pry apart. It is clipped together and double-sided tape on the battery also acts to hold the plastic shell together.
We can see that there is a set of nine 18650 cells, arranged as a 3S2P pack. The pack has proper balancing connections (thankfully), protecting it against cell imbalance and making the complexity of the pack comparable to replacement laptop batteries. The cells are YLE ICR18650A220, from YikLik rated at 2200mAh. In light of this, the total pack capacity is only 73.26Wh – close enough I suppose.
I wanted to know more about the switching converter PCB. It’s quite beefy and the aluminium plate serves as a heatsink. However, it wouldn’t budge, and this was down to two screws that can be accessed through holes in the heatsink. But if you’re going to undo them, you’re going to be releasing metal shrapnel into a circuit with a live beefy Li-Ion power supply connected. I don’t have the guts to do that … one short could well be catastrophic. As a result, that mystery will remain unsolved.
Testing the USB Output
As I didn’t have the appropriate connections to load-test the other outputs, I only tested the USB ports. The trusty B&K Precision Model 8600 was entrusted to perform the test. Despite the claimed 1A output, the unit always shut down immediately on 1A load, with an awful squealing noise suggesting it was critically overloaded. As a result, I had to test at 500mA which was a more sensible value.
The first day testing the first unit was quite an event as a heatwave passed through and the increased ambient seemed to cause the power bank output to drop slightly. Once night had fallen, the voltage recovered. Both units I salvaged performed almost identically, with just over 60Wh delivered at 500mA. This was more than I expected, as this is just over 80% of the label claimed value, or 82% of the actual battery capacity. When accounting for converter efficiency and battery ageing over at least five years, it’s a good result.
Being a little more daring, I pushed the current up to 800mA for a test. Unfortunately, the unit couldn’t sustain even 850mA, but the unhappy state of the converter is clear from the relatively low output voltage. No damage was caused, and the delivered charge was a little higher than the 500mA case, which was surprising.
In light of this, the USB output is actually quite limited in its usefulness. As a result, I didn’t bother assessing the ripple performance. Instead, I think I might use the other outputs with an outboard converter if I’m actually intent on using the unit.
I’m not too surprised that the unit didn’t seem to meet its claimed current output on USB. It’s endemic of a bigger issue – namely that of Chinese electronics which overstate their capabilities to try and appear better than the competition. Given the age and lack of reputation brand-wise, it’s not unexpected. I didn’t bother to test the ripple because it’s so painfully low that it’s not good for that much nowadays. However, when it came to output capacity, it’s nice to see that it could still manage a bit more than 80% of the rating even after half a decade or more.
Instead, it might be better just to use the laptop output or “quasi” 12v output (which might not be converted at all) into my own step-down converter to get a more beefy 5V output to charge a few devices at once.