Some time ago, I have reviewed an AA battery from XTAR, which is based on Li-ion technology with an integrated voltage converter. There is now a successor that comes with an integrated USB-C charging port, called “XTAR AA 1.5V 4100mWh USB-C”.
You can find the German version of this review on my website: SammysHP Blog › XTAR AA 1.5V 4100mWh USB-C
The batteries were provided by the manufacturer for this review. Thank you very much!
Different types of AA batteries
There are various battery types in the AA/Mignon size, which differ from each other in several details.
The classic: the alkaline battery (alkaline manganese, also known as “alkaleak”). A new battery has a voltage of around 1.5 V, but it drops continuously when discharged. It tends to leak, often damaging devices. It is also not suitable for high current output. On the other hand, it is particularly inexpensive and is therefore comes often bundled with new devices.
NiMH batteries, especially of the LSD type (Low Self Discharge), have advantages in almost all respects. As they can be recharged hundreds of times, they are more environmentally friendly and significantly cheaper than batteries in the long term. They do not leak and can deliver comparatively high currents. Their voltage drops quickly to around 1.2 V, but is then maintained for a long time. They are normally the preferred type.
In some cases, lithium primary batteries are advantageous. They are very lightweight, have a high capacity, can be stored for a long time and still work at very low temperatures. Their voltage is slightly higher at around 1.7 V, but most devices can cope with this. The disadvantage is their high price. They are well suited for devices with low power consumption or at low temperatures, such as wireless outdoor thermometers.
Similar in name, but completely different: Lithium-ion (Li-ion) rechargeable batteries, which are available in the same size as AA batteries (then called “14500”). When fully charged, they have a voltage of 4.2 V and can therefore not be used as a replacement for the other types listed here!
A special case is the battery type shown in this article, the Li-ion battery with 1.5 V regulator. This is a Li-ion battery that is equipped with a tiny, integrated voltage converter. This generates a constant 1.5 V from the 2.7 – 4.2 V of the Li-ion battery. This type always makes sense when devices have problems with the low voltage of NiMH batteries or partially discharged alkaline batteries. The disadvantage is the higher price.
XTAR AA 1.5V 4100mWh USB-C
The batteries are available as a set of four and come with a container for storage and a charging cable.
Detailed specifications can be found on the manufacturer’s website. The batteries have the size of a normal AA battery (50.3 mm long and 14.3 mm in diameter) and weigh just 20 g, almost a third less than a NiMH battery.
Nominal energy: 4100 mWh
Nominal capacity: 2450 mAh
Nominal voltage: 1.5 V
Discharge current: 2 A
Charging voltage: 5 V
Charging current: 0.45 A
Operation temperature: -20 – 50 °C
Storage temperature: -20 – 50 °C
Cycles: > 1200
Length: 50.3 mm
Diameter: 14.3 mm
Weight: 20.5 g
Their energy is specified as 4100 mWh, which in this case refers to the energy of the internal Li-ion battery. The voltage converter introduces losses, which means that a little less is available at the end. 2450 mAh, on the other hand, indicates the actually available capacity. In comparison, LSD NiMH batteries only have around 2000 mAh, and at a lower voltage.
Discharging
The batteries were discharged with an electronic load with a current from 250 to 2000 mA. The process was recorded using a four-wire measurement.
At a discharge current of 250 mA they achieved 2529 mAh, which is even 79 mAh above the manufacturer’s specification. Even at 1000 mA, they still come very close to their nominal capacity.
Here you can see one of the special features of these XTAR batteries: they do not provide a constant voltage of 1.5 V all the time and then suddenly switch off, but drop down to 1.1 V for the last 20%. This is intended to trigger the battery warning in devices so that the batteries can be replaced at a suitable time. On the other hand, this type of battery is used in devices that hardly work or do not work at all with low voltage.
According to the specification, the batteries are suitable for a continuous discharge current of up to 2 A. In the test the voltage dropped when reaching 3.3 A. However, at this load the batteries become quite warm already,
A problem with this kind of batteries is the electrical noise from the integrated switching regulator. There’s not much space for filtering and the regulator is run at high frequency. This causes issues with some devices like radio receivers or radio-controlled clocks.
Charging
Until now, a special charger such as the XTAR VX4 or the simpler XTAR MX4 was required for batteries of this type. However, the charge controller is usually integrated into the batteries, making the “charger” little more than a battery holder that supplies 5 V to the battery terminals.
This method still works with the new XTAR batteries. However, now there is also an integrated USB-C port, which can be used to charge the batteries directly without special hardware.
If you only want to charge a single battery, you can use a regular USB-C cable, same as you would use to charge a smartphone, for example. To charge several batteries at the same time, a special cable with a USB-A plug on one side and four USB-C connectors on the other is included in the set.
The charging current is around 470 mA for each battery. The USB power supply should therefore be able to supply at least 2 A for four batteries. During the charging process, a green LED flashes in the positive terminal of the battery, after completion it lights up constantly. In this state, only 360 µA are drawn through the charging cable.
The technical implementation is extremely simple: the USB port is connected directly to the terminals of the battery and thus powers the integrated charge controller in the same way as the aforementioned “charger”. This fact can also be used in a creative way: If you cut off a USB cable and connect it to the battery, the regulated voltage of 1.5 V is available at the wires - saving you a battery holder.
Conclusion
Even if NiMH batteries are almost always the right choice – in some situations you need an alternative. The new XTAR AA 1.5 V rechargeable batteries are a successful upgrade of their predecessor and now have an integrated USB-C port for charging. Thanks to the integrated voltage regulator, they deliver a constant 1.5 V for the majority of the runtime and a drop to 1.1 V at the end serves as a battery warning.
Another positive aspect is the manufacturer’s honest capacity claim. With a discharge current of 250 mA, the battery even exceeds its specification. The available capacity of 3600 mWh is significantly higher than that of NiMH batteries with around 2400 mWh.
The only disadvantage is the higher price and the noise in the output voltage, which can lead to problems with some devices.
