Soshine 14500 Lifepo4 Battery Kit 700 mAh

Today’s review is about batteries, but not the familiar Li-Ion ones—this time, LiFePO4.
For the most part, they’re very similar, but in reality they have far more differences than you might think at first glance, and I’ll try to cover them.


First, a little about what they are.
Lithium-ion batteries are extremely popular these days. They’re used in our smartphones, tablets, e-cigarettes, cordless drills, and even cars.
Of course, they have advantages—low self-discharge, high capacity, and good current delivery—but they also have their drawbacks.
Some of these drawbacks are addressed by batteries that use LiFePO4 as the cathode material. They’re called lithium iron phosphate batteries, though they’re more often simply called lithium iron or lithium ferrous batteries.

For a rough comparison, I put together a table based on data from Wikipedia. Of course, it doesn’t tell the whole story, since there are many different types of lithium-ion batteries. For example, some have a voltage of 3.7 V, while others are rated at 3.85 V. Some batteries are designed to provide high capacity in a small package, while others have lower capacity but can handle higher current.


Even so, you can see that lithium iron batteries have several key features:
A different nominal voltage
Long shelf life
A wider operating temperature range at the low end.

However, they store somewhat less energy than lithium-ion batteries.

There’s more information on Wikipedia, but to avoid overwhelming the reader, I’ll quote only the comparison section here.

1. LiFePO4 offers a longer service life than other lithium-ion chemistries;
2. Unlike other lithium-ion batteries, LiFePO4 batteries, like nickel-based batteries, have a very stable discharge voltage. This can greatly simplify or even eliminate the need for voltage regulation in circuits.
3. With a constant output voltage of 3.2 V, four batteries can be connected in series to provide a nominal output voltage of 12.8 V, close to the nominal voltage of a six-cell lead-acid battery. Combined with the good safety characteristics of LFP batteries, this makes them a promising replacement for lead-acid battery packs.
4. Using phosphates avoids the cost of cobalt and the associated environmental problems.
5. LiFePO4 has a higher peak current (and, given its stable voltage, peak power) than LiCoO2.
6. The energy density (energy / volume) of a new LFP battery is about 14% lower than that of new lithium-ion batteries.
7. LiFePO4 batteries have a lower discharge rate than lead-acid or lithium-ion batteries. Since the discharge rate is expressed as a percentage of battery capacity, a higher discharge rate can be achieved with higher-capacity batteries (more amp-hours).
8. Because their energy density declines more slowly, after some time in service LiFePO4 cells have a higher energy density than LiCoO2 and other lithium-ion cells.
9. LiFePO4 cells lose capacity more slowly than lithium-ion cells (LiCoO2 [lithium cobalt oxide], LiMn2O4 [lithium manganese spinel])
10. One important advantage over other types of lithium-ion batteries is their thermal and chemical stability, which significantly improves battery safety.
11. Cold-weather performance. For example, the A123 Systems ANR26650M1-B battery is rated for an operating temperature range of -30°C ... 55°C and a storage range of -40°C ... 60°C.


But let’s move on to the subject of the review. In this case, we’re looking at batteries from the Chinese company Soshine—though calling it a “company” is a bit of a stretch. To me, a company means something like Samsung, Sanyo, Sony, LG, and so on.
I ordered the batteries from GearBest and AliExpress, but it turned out they were identical, and even the prices were about the same. In both cases, the sets were additionally wrapped in a matte bag.


The packaging is a fairly bright blister pack.


The packaging lists the following specifications:
Nominal voltage - 3.2 V
Nominal capacity - 700 mAh
Charging current - 300 mA (standard), 600 mA (fast). Charge termination at 3.6 V
Maximum discharge current - 1.2 A, cutoff at 2.0 V.

Some of these specifications don’t quite match those listed on the store page, but I’ll get to that a little later.


The package includes more than just a set of batteries: it also comes with a plastic storage case and a pair of “dummy” cells—that is, empty cases with no internals, but the same size.


The four batteries were loose, while the “dummies” were in the case. They look neat on the outside, at least until you take a closer look.


On closer inspection, you can see that the printing is a little blurry, and the overall finish is worse than on branded batteries.
But something else caught my attention more. In the first photo, the large print says 700 mAh, while the small print in the second photo says min. 550 mAh, which is noticeably less than 700.
The positive terminal is like those on ordinary no-name batteries: a small nub.

The "dummy" cells look almost identical; the only difference is the word Connector on the label. The thing is, the voltage of one rechargeable battery is almost the same as that of two regular batteries, and the rechargeable cells themselves are AA size. So you can replace regular batteries with one rechargeable cell and one dummy, but only in devices that use an even number of batteries. With an odd number, the voltage will either be too low (1 rechargeable cell and 2 dummies) or too high (2 rechargeable cells and 1 dummy).


The dimensions are indeed almost exactly the stated 14x50 mm. They are slightly longer, but that is probably because of the piece of electrical tape stuck to the negative terminal.
The packaging said they weighed 27 grams. I don't know where the error was, but mine weighed 17 grams; the "dummy" weighs less than five.


Since these batteries require a suitable charger, which I don't have, I had to put together this setup, with a regular charger serving simply as a holder.
The battery was connected to a universal electronic load, which also charged it. Fortunately, it can be set to any required voltage.


Let's move on to the tests.
The test was run at a discharge rate of 0.2C, or 140 mA. The battery was charged at 300 mA, as recommended by the manufacturer.
During the test, capacity was measured at discharge cutoffs of 2.8, 2.5, and 2.0 V.

The result was this rather unusual graph, especially after testing regular lithium-ion batteries. Lithium iron batteries have a flatter discharge curve and provide a fairly stable voltage for most of the time. In that respect, they are somewhat like nickel-based batteries. Lithium-ion batteries, on the other hand, usually show a more noticeable voltage drop.
There are two other unusual things worth noting:
1. As soon as the charging current is switched off, the voltage at the battery terminals drops sharply to about 3.28–3.3 V, unlike with lithium-ion batteries.
2. Below 3.0–3.1 V, the voltage drops fairly quickly, and below 2.5 V the graph becomes almost vertical.

The test results were as follows:
1. Capacity at a discharge cutoff of 2.8 V: 520 mAh
2. Capacity in the 2.8–2.5 V range: 10 mAh
3. Capacity in the 2.5–2.0 V range: 4 mAh.

The results show that:
1. The capacity does not match the stated rating and is at most 534 mAh.
2. There is no point discharging below 2.8 V, since the difference was only 14 mAh.


There is one small caveat: the charge termination current was 100 mA, not 30 mA, because my load can't be set to a lower value.
On the other hand, even if that had made a difference, it would have been very small, since the charging curve also differs considerably from that of regular lithium-ion batteries:
1. There is also a "plateau" here, where the battery voltage changes very slowly.
2. Once the voltage reaches the set 3.6 V, the current drops very sharply, so lowering the cutoff threshold would have added very little.
3. Because the current drops very quickly at the end of charging, the battery takes noticeably less time to charge than a lithium-ion battery, where the CV charging phase can be relatively long.
In the end, charging a 534 mAh battery at 300 mA takes about 1 hour 55 minutes. In my opinion, that's pretty good, since the battery charges at full current in CC mode for most of the time, which shortens the charging time.
The charge took 550 mAh, so we have:
"Taken out": 534 mAh or 1.693 Wh
"Put in": 550 mAh or 1.880 Wh.
The battery's energy "efficiency" was about 90%.


After that, I tested the second battery for comparison.
The result was slightly better: total capacity was 546 mAh or 1.737 Wh, and charging took 562 mAh or 1.917 Wh. The "efficiency" was still 90%.


Then I got carried away and decided to see whether "conditioning" would make any difference. Predictably, it didn't improve anything.
The first battery was used for the next test, and the second cycle yielded 540 mAh instead of 534, a difference of about 1%.
Then I immediately repeated the same test with the same settings. Almost everything matched; the only difference was during charging, just 2 mAh. While I was at it, I checked whether my charger gives consistent test results, since Opus, LiitoKala and iMAX chargers sometimes produce different results on two or three consecutive tests.


Next, some tests at higher discharge and charging currents.
Charging at 600 mA and discharging at 600 mA.
486+29+17=532 mAh or 1.607 Wh, “efficiency” — 85%


We'll leave the charging current as it was, but increase the discharge current to 1.2 A. This is listed as the battery's maximum continuous discharge current.
The graph and discharge curve changed noticeably. Before, the battery delivered very little in the 2.0–2.8 V range, but now the readings in that section are higher.
The result:
Discharge — 426+59+26=511 mAh or 1.472 Wh, “efficiency” — 81.5%


At the end of the test discharging at 1.2 A, I took a thermal image. The battery was practically cold. I could have tested it at a higher current, but the voltage sags quite noticeably, which defeats the point of using it that way.


The final test was done after all the others to check whether anything had changed after several runs with different settings.
As it turned out, there was essentially no difference. The first three tests gave me 534 and 540 mAh, and this time it was 543 mAh. The difference is probably within the instrument's margin of error.


In conclusion, the batteries didn't even reach the minimum stated capacity of 550 mAh, let alone the advertised 700.
Of course, they can still be used, and I think they'll work quite well—for example, as replacements for the two AA batteries used in some devices.
But keep in mind that these batteries require a suitable charger.

Along the way, the tests also gave me a little extra experience and insight into the characteristics of lithium iron phosphate batteries. This type of battery is quite good in itself; it's a shame the implementation here fell a little short.

That's all from me. As usual, I'll be glad to answer questions and read your comments. Maybe someone can suggest more interesting batteries in this size at a reasonable price.