What You Should Know About Most Talentcell 12V Power Banks (and similar devices from other manufacturers)
Talentcell sells a line of small and light weight portable power banks which have become very popular among amateur astronomers over the years. Their easy portability means that they can be carried out to a dark sky location or taken to public outreach events to provide limited power without the added burden of a larger capacity battery. It also means that the power bank can be attached to the telescope mount or optical tube to minimize cabling. Advertised on Amazon as 12V batteries Talentcell's power banks are available at prices ranging from $26 for their 3Ah model to $88 for their 12Ah model which can really help to keep the cost of portable power low. One should expect that even the smallest capacity power bank should be enough to power a modest sized mount like a Celestron SE Alt-Az or AVX EQ mount, or a Sky-Watcher Star Adventurer along with a few accessories for several hours. I have used their 8.3Ah model to power a Celestron 6SE along with an analog video camera and 10" LCD when doing EAA at public outreach events.
I suspect that hundreds, if not thousands of amateur astronomers have been using these power banks for years completely unaware that they actually are not 12V batteries at all and do not even supply 12V once a load has been applied. I count myself as one so unaware for many years until I started seeing complaints on CloudyNights about problems using these Talentcells to power ASIAIR computers or ZWO AM3 and AM5 mounts all of which had a problem with the actual voltages supplied by the power banks. This prompted me to take a detailed look at the design of the Talentcell power banks. I eventually purchased 3 more Talentcells to run through extensive testing along with my original 8.3Ah model to demonstrate for myself that these are not really 12V batteries and do not provide an output voltage of 12V except when no load is applied.
It is important in this discussion to distinguish between the many Talentcell power banks which are advertised as "Lithium ion" or "Li-ion" batteries versus the 2 Talentcell models which are advertised as "LiFePO4 Battery Packs". Of the former I count at least 9 different models being advertised on Amazon as of this writing versus 2 models of the later identified as "LiFePO4 Battery Packs". So what are the differences between these 2 different types? First, the 9 models advertised a "Lithium ion" use LiNiMnCoO2 as the internal power cells. LiNiMnCoO2 (NMC) is a very common Lithium Ion cell used in many applications, primarily where weight is a key concern such as in ebikes, electric power tools, some models of electric cars including many models of the Tesla, and in most of the portable power stations like the Jackery sold to date. NMC is considered one of the safest Lithium cells with a thermal runaway temperature second only to LiFePO4. Power supplies with NMC cells are usually rated for ~500 full discharge cycles after which 75 - 80% of the original capacity remains. In contrast power supplies with LiFePO4 are rated at 4,000 or more full discharge cycles which is why these are found in the batteries used in RVs and boats. LiFePO4 cells are now beginning to show up in portable power stations from Jackery and others.
The other main difference between NMC and LiFePO4 cells, and one of the keys to understanding the problem with many of the Talentcell power banks, is their nominal cell voltages. NMC has a nominal cell voltage of 3.6 to 3.7V. That means when fully charged it has a useable energy capacity starting at 3.6 or 3.7V. On the other hand, LiFePO4 has a nominal cell voltage of 3.2V which actually makes it an ideal lithium cell type for creating a 12V battery as 4 of the LiFePO4 cells in series will provide 12.8V. On the other had, 4 NMC cells in series will provide 14.4 to 14.8V which is too high for a typical 12V system. This is why a Jackery portable power stations using NMC cells have an internal voltage regulator to keep the output voltage in the 12V to 13.2V range throughout 100% of its depth of discharge (DOD) at which point the internal BMS shuts down the output. In contrast, a 12V battery using LiFePO4 cells does not need a voltage regulator so its voltage remains above 12.0V throughout 95% of its DOD. The voltage versus capacity curves shown above for LiFePO4, LiNiMnCoO2 and a lead acid battery demonstrate this quite clearly.
So why do I say that the Talentcell power banks using NMC cells are not 12V batteries? To understand this we need to take a look at the design of these power banks. Here we have Talentcell's own advertised design information which shows that they are using 3, not 4, NMC cells in series and then adding multiples of these in parallel to increase the capacity as needed. Here is an image of their 6Ah design which has 6 total cells configured as 2 parallel banks of 3 cells in series. The 3 cells in series can only produce 3 x 3.7V = 11.1V , not 12.8V. Interestingly, if you look closely at Talentcell's own specifications you will see that they indicate 11.1V 6000mAh for the capacity in the technical details for this battery, not 12V 6000mAh. (6000mAh is 6Ah). Yet, looking into the technical details you will see the output rated at a voltage range of 12.6V-9V. So where do they get 12.6V from? Well, let's take a look at the discharge curve for a LiNiMnCoO2 cell from Panasonic. These curves are for different discharge currents but each shows that while the cell can be charged to as much a 4.2V, the voltage drops below 4.0V, even to 3.7V depending upon the discharge current, as soon as a load is applied. With no load applied, 3 cells at 4.2V will show a voltage of 12.6V which is what the Talentcell spec is referencing. But with even a small load the voltage drops immediately below 12V because there is essentially no capacity in the cell above 3.7V.
To confirm all of this I purchased 2 of the power banks utilizing the 3S design with NMC cells, a 6Ah and a 12.8Ah version added to the 8.3Ah version I already had. I also purchased a 6.5Ah Talentcell power bank using 4 LiFePO4 cells in series for comparison. I ran each of these through a full discharge cycle test after first fully charging them per the manufacturer's instructions.
The measured capacities for each power bank are shown in the accompanying table. I used a load current at least half the rated current for each power bank in the capacity test to avoid stressing the battery. In the case of the 6Ah power bank I also used the maximum rated current of 3A to see if the measured capacity differed. Only the power bank with the 4S design using LiFePO4 cells met the rated capacity while the other 2 new power banks fell short by 5 and 15% respectively. I did not expect my 6 year old 8.3Ah power bank to match the rated capacity since I did not care for it well over its lifetime. More important than the rated capacities is the voltage versus capacity curves which are shown in the graph below. There are two curves for the 6Ah power bank since I measured this at both 1A and 3A loads. The curves show that while the no load voltage is 12.6V per the spec, the voltage drops below 12.0V as soon as a load is applied. For all 3 power banks the voltage drops below 11V with 70% of their rated capacity left which is quite amazing for a battery sold as a 12V battery. While lots of 12V equipment, including our typical astronomy gear, has a wide voltage tolerance, they are not designed to operate optimally when the voltage drops this low. This is clearly why the ZWO ASIAIR and AM3 and AM5 do not like these power banks. Even more amazing is the fact that these batteries drop below 10V with 30% of their capacity remaining. Even if your equipment works down to 10V, you are not getting the capacity you are paying for with these power banks. Looking at the 3A load curve for the 6Ah battery we can see if we push to the maximum current of the power bank the voltage drops even more precipitously and we can expect our equipment to quit or, at least, complain much sooner.
So, why is this happening? Well I can only guess as to the reason that Talentcell uses a 3S design with these 9 different 12V power banks. First, with less cells they save space and weight which helps to keep the power banks small and portable which is their main selling feature. Also, by not using a 4S design they save on the cost of additional cells and the cost of the voltage regulator that would be required to drop the voltage into a typical 12V power supply range. It is the simple fact that they use 3 cells in series and not 4 with a voltage regulator that these are not really 12V power banks.
On the other hand, the 4S designs with LiFePO4 perform perfectly as expected for a 12V battery and are the only ones that I recommend. As the voltage versus capacity curve below shows, the voltage stays above 12V for about 90% of its rated capacity with a load of 2A which is ~36W of power. If you push the power bank to its maximum current capacity of 5A the voltage drops more quickly but stays above 12V for ~66% of capacity and doesn't drop below 11V for 95% of the total capacity. Talentcell currently has one 4S model which uses LiFePO4 cells and has a capacity of 6.5Ah, which is model that I bought and tested and which be can found here. And if you need more capacity than that, here is a 12Ah LiFePO4 battery from Talentcell which is not a power bank but is still small enough to fit in the palm of a hand. ( Links are affiliate links).
Talentcell is not the only one using a 3S design in their "12V" batteries. A short survey on Amazon found several other manufacturer's of power banks doing the same thing. And, amazingly to me, I found that even some of the portable power stations available such as the EBL 300Wh model specifies a DC output voltage of 9 - 12.6V just like the Talentcells with a 3S design while the EBL models 500 and 100 (which I tested and reported on here) specify a DC output voltage of 11.8 to 14V which is consistent with a 4S design with NMC cells and a voltage regulator. So my suggestion is to look carefully at the specifications before you buy.
If you want to see more on this topic, I made of video showing exactly how I tested the 4 Talentcell power banks which I bought and which you can find on my Youtube channel.
These are the only TalentCell power banks that I would recommend, along with a 12Ah LiFePO4 battery if you need more power. Links are affiliate links which can earn a commission without any cost to you and help support this web site.
Talentcell 12V LiFePO4 Battery 12.8V 6.5Ah 83.2Wh - amzn.to/3NYIPxD
Talentcell 12V LiFePO4 Battery 153.6Wh 12.8V 12Ah: amzn.to/3SfDMM0