Review, Teardown: “Quality Assurance” LP-406B 5200mAh White Power Bank

The next cab off the rank is this relatively generic looking power bank. Packed in a cardboard glossy colour box with window, there’s no trace of any manufacturer on it – merely the words “quality assurance”. I suppose I’ll use that as the name for this power bank.

DSC_6632It has a really generic blurb on it with no mention of capacity, so I don’t think the box necessarily describes the product inside – but it does list “five security protection” which is a bit questionable. I highly doubt there is colomb counting fuel-gauging which is why a current shunt would be needed, and intelligent control circuits doesn’t mean much.

DSC_6633It claims it is made with A+ grade batteries, and claims to be able to be used for charging while outputting as well. It claims a conversion efficiency over 85%, however, it is listed as producing a constant current. Hmm. I don’t think that’s what they mean.

It lists an input of 1A, which allows for quicker charging, although 7-8 hours is specified. The output is 1A, suitable for phones but sub-optimal for tablets. Other models with dual outputs have different configurations, but it doesn’t apply to this model.


The bottom of the box does have a fairly ominous warning, and the obligatory spelling mistake.


The package includes a user manual, which is merely a small leaflet, the power bank itself, and a basic short microUSB charging-only cable. The power bank itself has very generic printing on it with no specific branding.


The power button and four blue indicator LEDs are placed on the front of the unit. A single output is provided on the top, rated at 1A, with a 5mm white LED as an “emergency torch”. The power bank automatically activates when a load is connected. There is the microUSB B charging input on the left side. The underside of the power bank also has its ratings printed on it (not pictured).

Activating the torch requires pressing and holding the button. The mode can be toggled between on and SOS, although the brightness is very limited.


For all these reviews, to avoid damaging the unit before its performance is tested, I perform the teardown after the tests are completed. In this case, I wished I had performed the teardown before the testing was done.

The battery is secured by adhesive, and prying around the edges eventually gets the halves to separate.


The power bank itself uses pink-coloured cells, which would have you hopeful that they are Samsung cells … but lets find out.


The conversion circuitry itself is housed on one main double-sided PCB with the indicator LEDs connected on a secondary PCB soldered to the main PCB. There is a hole cut-out in the middle to allow the power button to be accessed. The top PCB is marked with LP-406BV1.2 dated 2012-07-10. From this, it seems that there are many power banks being resold with this code, but it is possibly related to this listing by Shenzhen Blue Times Technology Co. Ltd.. It has been seen with many different capacity levels ranging from 4400mAh to 5600mAh.


Underneath the indicator LED PCB, it seems a microcontroller (with its markings ground off) does most of the work, as usual.


A switching MOSFET, a Schottky diode and a tantalum capacitor is visible in the other side. There is no large bulk electrolytic capacitor to smooth the output however.


The underside of the PCB seems to show a charger IC and the LED, however also provides evidence of critical damage to this unit. The inductor itself is broken, and thus, it may not be providing the right value of inductance, thus negatively impacting the converter’s performance in regulation, ripple and efficiency.

This may be due to poor quality component choice, errors in assembly and lack of QC or extreme handling damage.


While the cells themselves share the Samsung heatshrink colouration, they are definitely not Samsung cells, despite a similar coding. They have fairly good weight, and claim to be 2600mAh each, making a total of 5200mAh for this power bank.

Performance Test

Unfortunately, as it was discovered during the teardown that this sample is an atypical example of this product, the following results may not apply to your product. The damage to the inductor is likely to have caused the power bank to under-perform, however, does raise questions of QC issues and performance in the case of having a properly functioning inductor.

Testing was performed with the new rig, following the same methodology as the other tests. However, because this example is atypical, the performance recorded is not likely to be completely representative of this type of unit.

Load (mA) Run Capacity (mAh)
500 1 3343.249357
500 2 3457.86689
500 3 3417.50065
500 4 3456.79494
500 5 3440.686773
Mean 3423.219722
Range 114.6175327
StDev 47.59408162
Load (mA) Run Capacity (mAh)
1000 1 3203.918884
1000 2 3369.772723
1000 3 3400.094847
1000 4 3314.408747
1000 5 3222.401297
Mean 3302.1193
Range 196.1759628
StDev 87.07109971

The capacity test produced a relatively poor result of 2423mAh and 3302mAh at 500mA and 1A loads respectively. If the cells were actually 5200mAh, this would mean an efficiency of 65.8% and 63.5% respectively. I think it’s fairly probable that this may be the case as the loss of efficiency due to inductor damage is a reasonable expectation. This power bank also keeps the LEDs on during discharge, which further degrades the efficiency figure by consuming power.


With the damaged inductor, the power bank failed to provide regulation at 1A loads. The voltage fell below the minimum allowable 4.75v almost immediately and continued to plummet to nearly just 4v at the end of the run. Loads at 500mA showed decent regulation but a high voltage of 5.2 to 5.25v. This average voltage is within the 5.25v allowable range and could help offset voltage losses in thin microUSB cables, however, is a bit high for my liking.

This is especially the case when ripple is considered.


At 500mA load, the ripple measured 1074mV, which is miles above the expectation of ~ 150mV. More capacitance on the output might mitigate some of the very sharp spikes. The frequency of oscillation is about 878kHz which is moderately high.


At 1A loading, this increases up to 1535mV which is way too high. Connecting this to USB devices may cause damage over time, stress or erratic operation. The maximum range of USB voltage is 4.75V to 5.25V, a span of just 500mV worst case.

This is somewhat expected when the inductor failure is considered.


After consideration of the teardown’s discovery of a damaged inductor, a fair assessment of the performance of this power bank is not possible. However, it is shown that a damaged component on the PCB can produce fairly poor quality power. Whether this power bank performs well with correctly functioning components is still questionable, especially given similar ripple magnitude from “properly” functioning Chinese power banks in the past. I’ll chalk this one up as inconclusive.

About lui_gough

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