I bought 40 pieces on the Aliexpress cheap batteries are very similar to the Samsung INR18650-25R. It is assumed that the pair will test at high and low currents and I will do the assembly for rechargeable mowersBut I had to test everything.
Seller, pretending to be the manufacturer, resulting in quite a few options:
"Model: INR18650-25RM
Type: Li-ion battery 18650
Rated capacity: 2500 mAh (2400-2500 mAh)
Nominal voltage at 3.7
Weight: 45g ± 1g
Internal resistance: ≤20mΩ
The limited charge voltage: 4.2 in
Operating voltage: 2,75-4,2 in
Size: 65.5 mm x 18,5 mm
Working time: up to 500 times
Place of Origin: Hong Kong "
20A maximum current is specified only in the name of the lot.
Sticker "Liitokala" pasted over the place where most likely written "Samsung", but with very high probability, these batteries are a copy of the original Samsung INR18650-25R.
But since there is no precise technical specifications, have yet to check out samsungovsky datasheet:
Original batteries can be charged current to 4A and discharge current up to 20A, the discharge voltage is admissible to 2.5V.
I'll start with the good. :)
33 out of 40 purchased battery did not cause any issues. Their discharge capacity at current 2.5A (1C) until the voltage is 2.5 V 2500-2650 mAh (9-9.52 Wh).
When the discharge capacity decreased to 3V at 80-90 mAh.
10A, at a discharge current batteries are capable of delivering only 9% less energy.
Full charge for this current takes less than 16 minutes. After ten minutes of continuous discharge battery is warmed to 52 °, after 12 minutes to 57 °, after 14 minutes to 60 °, the maximum temperature was 64 °.
18A during the discharge current of the battery temperature in a minute was 39 °, two minutes 49 °, three minute 62 °, 77 minutes at 4 and after 4.5 minutes from the beginning of continuous discharge battery warmed up 89°. After that, the experiment was stopped, but the shell of the battery managed to slide from such heating.
For one experiment, the battery was charged at a current 4A. When charging, it is almost not heated (less than 30 °) and successfully charged. All other batteries charge current of 1.3 A.
Incidentally, when the discharge current of 2.5A batteries almost no heat (temperature below 30 ° C).
And now for the bad.
The first step after receiving the battery, I measured the voltage of each of them. At the first instance of tension was much lower than normal - 0.649V.
Caught two more battery low voltage - 1.532V and 0.883V. All other batteries have a voltage 3.529-3.626V.
Using three laboratory power supply with a low voltage battery have been successfully charged (conventional battery charger with low voltage charge refuses) and showed quite normal capacity - 2520, 2620, 2580 mAh. But how they will behave in the future to say difficult.
two batteries still have a significantly lower capacity than the rest - in 2160 and 2170 mAh. Three-time charge and discharge has not changed anything.
two batteries still have a slightly lower capacity than the rest - 2390 and 2450 mAh.
A few words about the purchase.
Batteries come in a box from the charger.
Every five batteries are packed in two soft bags.
If God forbid the post office box that strongly knocked, could and to flash.
I bought batteries on sale in lots of 10 pieces of $ 1.496 per share (with coupons turned less than 90 rubles apiece). Now the seller removed the lot (maybe they remove the lot as soon as the negative reviews there are accumulated). Lots of these batteries with the seller several, in the cheapest 20 batteries sell for $ 35.52, ten for $ 19.12.
I'll tell you how I conducted experiments.
To charge the battery to use the universal charger iMax B6 in balancing mode. Charging current - 1.3A (0.5C).
To measure capacitance I used Oleg analyzer ArtamonovaCapable of providing up to 2.7A load current. To create high currents had poizvraschatsya. I have four tester EBD-USB +, each of which gives a load of up to 4A. I soldered them thick wire and connected with wires terminating chetyryroh EBD-USB + and analyzer. In this case, test leads from the four-wire Holder went to the analyzer and allowed to accurately measure the voltage in the testing process.
All this mess is controlled by two computer. On one testers were asked discharge currents EBD-USB + (4x2A 4x4A and 10A for current to 18A), the second worked analyzer control program (2A discharge current).
To the screenshot analyzer were shown the correct results, rather than five times less than in the discharge current data file has been replaced from 2000 mA to 10000 mA.
All this "battery testers" could create a current of 18A discharge 20A but do not work. I think the difference is small and everything is clear.
In spite of all this "farm", a fairly accurate measurement, and did not need to buy a powerful load.
Batteries Liitokala INR1865025R really withstand high currents. They can discharge current 10A from the beginning to the end, thus they are heated to an acceptable 64 ° C. Current 20A, these batteries also withstand, but not more than 3 minutes at a time, after which they need to cool down. the battery has a capacity of 2500-2650 mAh (9-9.52 Wh), moreover at high currents capacitance decreases less than 10% (8.63 Wh). Batteries can withstand high current charging (4A), but it is better, from harm's way, they charge current up to 2.5A.
Be prepared for the fact that a small part of the battery of the parties will be worse than others, and their better not to use in the general assembly and prior to use all batteries have to be tested for capacity. Batteries, find themselves discarded, can be used in lamps, power tools, pauerbankah.
In my case, of the 40 batteries in the assembly will 30 of the best, and the remaining 10 can be used for other purposes.
© 2019 Alex Nadozhin
The main theme of my blog - Equipment for human life. I write reviews, share experiences, talk about all sorts of interesting things. My second project - lamptest.ru. I test LED lamps and help figure out which ones are good and which are not.