XTAR has released a new model of a protected 21700 battery, the XTAR 21700HP 5000mAh 25A. I received two samples for testing, here are the results.
You can find the German version of this review on my website: SammysHP Blog › XTAR 21700HP 5000mA 25A
First the official specifications of the new model:
Nominal capacity: 5000 mAh
Nominal voltage: 3.6 V
Discharge end voltage: 2.5 V
Discharge current: max. 25 A
Charging voltage: 4.2±0.03 V
Charging current: 2.5 A
Storage voltage: 3.6 – 3.9 V
Over current protection: 25.5 – 35 A
Operating temperature: -20 – 50 °C
Storage temperature: -20 – 50 °C
Internal resistance: < 23 mΩ
Cycles: > 500
Length: 74.8±0.5 mm
Diameter: 21.5±0.3 mm
Weight: 73 g
The batteries have arrived at 3.60 V. I measured their length at 74.9 mm, diameter at 21.4 mm and weight at 70.0 g. This makes them the shortest protected 21700 batteries in my collection. However, they are still almost 5 mm longer than unprotected batteries and therefore do not fit in all devices.
It has a protruding positive terminal (button-top). Could be about 1 mm shorter without it.
Apparently the protection circuit is located at the negative terminal, where you can see a gold plated PCB.
For my tests the battery was charged with 2 A to 4.20 V before each run. After 15 minutes the battery was then discharged with an electronic load, while the voltage was measured separately (four-wire measurement). Unfortunately my load is limited to 10 A, so I was unable to test at higher discharge currents. At the end of the 10 A measurement the battery had a temperature of around 50 °C.
I stopped the tests at 2.8 V, as most flashlights no longer work properly or switch off below this voltage anyway. Down to 2.5 V it would probably be possible to extract a little more energy from the battery.
My charger (Gyrfalcon S8000) measured an internal resistance of 15 to 18 mΩ, which also matches the voltage drop when the load is applied.
Overall the XTAR 21700HP makes a good impression. For a protected battery, it delivers good results in terms of discharge current and internal resistance. This also makes it suitable for high performance flashlights.
