This post actually came about because I was chatting with Robert about a few electronics and computing related things when he mentioned that he owned a power bank himself. Knowing from past experience that some power banks are really not up to the mark in regards to capacity, I was slightly skeptical.
The power bank in question was the Comsol 11000mAh Dual Output Power Bank in white. Available from Officeworks for AU$69 at time of writing, it’s a fair price for a power bank of that capacity if it proves to be genuine. I wasn’t aware of Comsol as a brand, as many are just import-and-rebadge operations, so I was interested in seeing whether the power bank was truly 11000mAh as it said it was.
Luckily for me, Robert was mutually interested in this, and lent me the power bank for testing. I kept it for two and a half days of testing, and it definitely took most of the time to get it done and the numbers took another hour or so to prepare.
The Unit
As this unit was already in use and loaned to me, I have no idea what the packaging looks like, but the unit itself is best described as a rounded rectangular brick, which is about 2×3 18650 cells in size roughly. It seems to likely accommodate 2×2 18650 cells, with the remaining space for the power conversion PCB and USB sockets.
If it did indeed contain four 18650 cells, each would have to have a capacity of 2750mAh. This is a “premium” capacity (anything above about 2400mAh per cell starts commanding higher prices) but well within the reach of 18650’s (now capable of 3400mAh per cell). The pack is solidly built with a moderate amount of weight to it. All are good signs.
The long edge on one side contains four blue LED power indicators, two outlets (one 1A, the other 2.1A), a microUSB B socket for charging and the power button. The power bank powers up automatically upon connection of load, and the LEDs remain off during use 
(which saves some energy, unlike some others that I’ve tried). A quick press on the power button allows you to check the capacity, whereas a long press allows you to activate/deactivate the single LED torch …
Not that it’s really much of an impressive torch. Maybe if you’re desperate for one … on the plus side, it’s unlikely to run out for a long time!
The underside is marked with the model number PB-02-11000-WHT and claims a capacity of 11000mAh. It also claims the input to be 5v, 2A.
Connecting it to my Asus/Google Nexus 7 2A charger required a total time of 7.5 to 8 hours to fully charge from flat. This is not a definitive indicator of capacity, as it depends on the charge current, but at 2A for 8 hours gives up to 16,000mAh consumed from the wall (assuming a linear-type charger IC which drops the additional voltage, as opposed to a switching type). It’s likely to be less, as the charge rate tapers off towards the end of the charge.
Testing
It’s been a while since I’ve tested power banks, but I’ve used the same setup as the test before, although the sample time may have changed slightly. In this case, we get 83 samples per minute, for a just above 1hz sample rate (more than accurate enough for our needs). The same USB plug lead to 5 ohm / 2.5 ohm switchable load is used.
Due to time constraint, three runs at the 2.5 ohm (~2A) load and one run at the 5 ohm (~1A) load were performed. The real current was about 1.62A and 0.9A respectively, likely due to the voltage drop in the USB plug and ~20cm of lead. As a result, it’s likely that the results will underestimate the true capacity slightly, but reflect what a device is likely to experience in reality.
The results are as follows:
Comsol 11000mAh Dual Output Power Bank Summary 2A Run 1 8794.897118 mAh 79.95361016 % efficiency 2A Run 2 8873.072372 mAh 80.66429429 % efficiency 2A Run 3 8811.414383 mAh 80.10376712 % efficiency 1A Run 1 9848.097881 mAh 89.52816256 % efficiency
The values for the 2A run imply that somewhere around 8800mAh of capacity at a nominal 3.7v was extracted and is remarkably consistent (range of 78mAh). The test rig itself is really only good to provide indicative values within about ~7.5% mainly due to resistive cable losses. If the power bank was truly 11000mAh, this would put the efficiency around 80%.
The value for the single 1A run produces a result of about 9848mAh of capacity – more than the 2A run likely due to less resistive losses in the USB cable. The efficiency shoots up to 89% which is very good. (Slight change to value, as under the 1A test, there are 81 samples/60 seconds, rather than 83 samples/60 seconds.)
When you account for the voltage drop in the cable (assuming the output is exactly 5v), there is about a 2% loss under the 1A run, and a further 4.6% loss for the 2A run. This brings the conversion efficiency up to 87-91%. This is an excellent result, no doubt aided by genuine batteries and LEDs which remain off during use.
The voltage profile reveals something interesting about the way the power bank operates. It seems likely that this power bank is produced using a microcontroller of some sort, which samples the output voltage and adjusts the duty cycle stepwise to maintain the output voltage within a certain range. As the battery begins and finishes its discharge, the voltage of the battery changes quickly, which means the duty cycle required needs to step quickly as well (hence the bunched up saw-tooth patterns). In the middle of the discharge, the lithium ion cells maintain a fairly stable voltage, so the duty cycle changes are less.
This regulation looks bad on paper, but is very decent given the amplitude of the voltage changes are about ~0.05v (50mV). It’s the first power bank where the voltage regulation steps are as coarse and can be seen so clearly. It implies that the duty cycle of the converter is not continually adjustable and implies a digital control.
There’s also no need to worry about over discharge as the output is isolated once the power bank switches off automatically when it runs out of charge.
Conclusion
Rather unexpectedly, the Comsol power bank appears to be very much a genuine power bank. Its capacity under test was as expected when you consider power conversion and resistive cable losses, and the price of AU$69 may seem expensive compared to the eBay unbranded units, however, it offers a capacity twice as much as the “30000mAh” fake power bank. In all, it’s actually quite reasonable if you look at it that way.
Its performance is very much acceptable, and its capacity is sufficient to charge up most 7″ tablets twice, and phones about three to four times. I would recommend it mainly on the fact that its capacity is genuine from what I can tell, although taking it apart was not an option.
I took one of these on a 13 day bus/camping tour (2014) and it was a godsend – kept the phone charged up when there was no access to secure power outlets. A very good backup for travellers.
how much price this it PB-02-11000-WHT
You will have to see if any retailers near you have it for sale. In Australia, this product is available through Officeworks for AU$79.
– Gough
For my power bank of eloop, it takes nearly 10 hours to chagre fully from neutral. Is the time taken by it is similar in comparision to other power banks? Also is it ok to charge it with the charger of mobiles or other chargers???
Yes. Large capacity power banks commonly take 6 to 14 hours to charge depending on capacity. Charge speed is limited by several factors, including the configuration of the charge controller inside the power bank, the losses in the cable connecting it to the charger, and the charger’s ability to supply current.
– Gough
I bought a Comsol PB-02-11000-WHT power bank in Melbourne at Officeworks about 1 yr ago and used it about 10-15 times during this time. I now I find that it will not accept a recharge; the blue light flickers 24 times then goes out but no charging occurs, and the torch has zero light emission. I do dot believe I’ve done anything to contribute to failure of the unit and do not know if a warranty would extend past 12 months.
Does anyone know if it may be repairable or if batteries may be economically replaceable?
It appears that maybe the cells have gone short circuited or ended up in protection due to over-discharge. As power banks in general are relatively inexpensive items, I don’t think repair is going to be cost effective unless you do it yourself.
It’s likely that the power bank either has 4 or 5×18650 type cells. Quality cells are about $5 a piece, so that’s already $25 there. The cases are usually not designed to be opened without a fight, so cosmetic damage is the least you can expect. Cells cannot be soldered directly to, so you will need some tabs and access to a battery spot-welder. Not even I have one of those, but maybe you know someone. After the pack is assembled, then you need to solder the end tabs to the wires connecting to the board inside, and pray that the fault is not within the board itself (e.g. failed microcontroller/charge controller/etc), otherwise it might not work, or might damage another set of batteries.
Based on the hassle – I don’t think it’s worth it.
– Gough
Recently I’ve been looking at purchasing a Comsol 11000mAh Power Bank. I’ve researched a few brands, and found the information very interesting, but irrespective, I would rather know that the item purchased was in fact genuine, and the Company selling the product was able to supply accurate information.
I’ve recently emailed this company (Comsol) with the following question:
“Can you kindly advise at what rate a fully charged Comsol 11000mAh Power Bank Batteries would lose it’s power, if not used ?”
This is the reply I received:
“Sorry we don’t have any data on how long the power bank will last while not in use.
Think of it the same way you would your phone. How long would it last if you charged it
then just left it not in use. Similar sort of thing.”
Interesting reply, which I’m happy to supply to you, personally.
We were hoping to purchase a Power Bank that would have a long lasting charge still left in the Batteries (if not used), similar lasting charge to our li-ion lithium for our Ryobi.
We only have 2 Mobile Phones, and a WiFi Keyboard, at this stage, but wanted to ensure that we purchased an item that has long lasting charge, if not used. I would appreciate your reply.
I would have to concur that their reply is probably the only reply a company who didn’t actually engineer the internals of the product can provide. Even if a company did engineer the internals, there are too many variables to consider.
How quickly a battery or power bank would deplete itself if left alone is a multi-factorial issue. You have to contend with:
– Quiescent draw of the circuitry (e.g. microcontroller) which may always be running in a low power mode ready to respond to button presses by an interrupt trigger.
– Leakage in any switching devices (e.g. MOSFETs) which are supposed to be off when powered down but have an infinitesimal leakage current.
– Battery self-discharge, which can vary depending on the batch/manufacturer of the cells and how many cycles they’ve done and if there are any “freak” impurities which may have gotten in.
– Temperature that it is stored at – leakage current is often dependent on temperature, as well as any self-discharge.
– Humidity (potentially) or dirt on contacts – some units have their outputs almost always energized ready for load-detection and switch on – any dirt and humidity may cause a very tiny current drain to form.
– Leakage and dissipation in any output capacitors – this applies where outputs are always energized, as ideal capacitors don’t end up having any dissipation, real-life capacitors are rarely so ideal.
– Loss in quiescent current of any dedicated cell protective devices – only this applies to most battery packs – power banks have the active circuitry meaning there are many more items to consider.
If you asked me to recommend you one that wouldn’t drain too quickly if left alone – I couldn’t really say nor guarantee it without actually breaking connections and doing micro-power measurements and even then, something “else” could happen in the interim and make it moot. It also depends on how much power you’d like to have remaining at the end of a given period, but on the whole, good Li-Ion cells shouldn’t have any real appreciable self-discharge, but more likely will have irreversible capacity loss if stored full charge all the time due to voltage stress on the separator.
That being said, in my experience. I’ve stored even cheap power banks and none of them have self-drained by any more than 20% per year. The larger the capacity, the less likely there will be any significant loss of charge as the quiescent current should be pretty similar but the power reserve is bigger. Any quicker depletion and you’re probably facing a circuitry or battery fault.
– Gough
Many thanks for your reply. We appreciate the time you have taken in outlining all the conditions that can affect Battery life. The information you have provided is amazing. I know that this will be of massive value to visitors of your Web Site, and it doesn’t’ stop there as those readers will pass this information of to others. I’ve also researched many of the terms you’ve used, to assist in my understanding.
After reading the information that you’ve compiled in reply to my question, I’ve now looked at Li-ion cells, not realising that there are different types being Lithium-ion or Lithium-polymer cells.
With all your expertise, may I ask, which type would you suggest to be the more favourable in a Power Bank to be used for 2 Mobile Phones, and a WiFi Keyboard, at this stage ?
I’ve typed up the information that was on one Web Site, and it states:
Lithium-ion:
– Energy Density: (amount of energy stored in a power bank) Higher energy density
– Aging: Loses its actual charging capacity over time
– Chances of explosion: Likely to explode when overcharged
– Charging duration: Longer charge
– Weight: Little heavier
– Conversion rate: (the capacity to convert battery into actual power) 85%-95%
Lithium-Polymer
– Energy Density: (amount of energy stored in a power bank) Low energy density
– Aging: Does not lose it’s charging capacity as much as Lithium-ion
– Chances of explosion: Safe from Explosion
– Charging duration: Comparatively shorter charge
– Weight: Lightweight
– Conversion rate: (the capacity to convert battery into actual power) 75%-90%
Again your reply would be appreciated.
Kind regards
It really depends on what your priorities are. Lithium Polymer and Lithium Ion are remarkably similar – when it comes to practical usage, LiPo is considered “safer” with failure modes that should mostly avoid any “explosions” under mild mistreatment, and they can be lighter, and put into smaller shapes because they don’t need metal casing. Li-Ion cells are mostly cylindrical, metal shelled, so they tend to be less closely packed together and heavier, but they can be slightly more dense for energy. They are a little easier to get in the “branded” quality variety – e.g. from Panasonic, Samsung SDI, etc.
For an average consumer, they really probably don’t need to care about the intricacies, but the summary you’ve provided is pretty much correct. I’d suggest focusing on the more important things – e.g. warranty, physical size/weight constraints, charge rate of the power bank/charge rate of the devices (some are more compatible than others, large power banks can take excruciatingly long time to charge depending on rate/technology e.g. Qualcomm Quick Charge 2.0/3.0), capacity needs. I’m guessing that if you want a larger power bank (e.g. 16,000mAh+), then most of your options will be Li-Ion, whereas below about 10,000mAh, you will find some Li-Poly options although mostly Li-Ion probably because 18650 cells are relatively abundant and inexpensive.
– Gough
I had a10000mAh, model number DPA10RG and today it exploded in my face , I noticed a small red spot in the bottom corner and then it just spontainiously combusted in my hand.
It is mentioned in this article that the power supply voltage output mode uses a regular duty cycle, and there is no ripple and noise testing item in this article. It is because the ripple and noise value measured by the instrument will be very large. such ripple and noise testing is meaningless?
Thanks.
I still have this unit, it functions ok but takes a long time to charge (now at 18 hours it’s only up to 2/4 charging status lights).
It’s been a solid reliable power bank in it’s time.
I was looking on their site, they don’t sell power banks anymore it seems.