18650 battery test 2011
A 2012 test can be found here
In this test I have measured many different 18650 batteries and collected the data in bar graphs and curves. The above picture shows most of the cells I have tested.
Capacity: Measured capacity at 0.2 ampere discharge rate (This is the average from the two tested cells). This is not measured the same way as the manufacture specified capacity, i.e. it is not supposed to be exactly the same value.
Top: SB: Small button top, LB: Large button top, Flat: Flat top (See here for more information).
Bottom: A protected battery has a PCB at the bottom, on some batteries this has been strengthen with a metal plate.
Protected: Does the battery have a protection circuit? IMR batteries do not.
Max. Dis.: Maximum allowed discharge rate. This is only listed for batteries where it is specified, for all other batteries assume 2C.
Source: Where I got the battery.
Date: The month I got the battery.
This chart show the average capacity of the tested cells.
This chart show the average energy of the tested cells.
In this chart I have taken the difference between 0.2 and 2 ampere energy bar and calculated the change in percent of total energy ((Energy@0.2A - Energy@2A) /Energy@0.2A). This high lights the difference on handling loads.
18650 batteries are not all the same size, they are supposed to be 18 mm in diameter and 65 mm long, but due to the added protection circuit they are up to 5 mm longer. These charts show the size of the largest of my test batteries (The difference is usual not more than 0.1 mm to 0.2 mm for a cell type).
Combined discharge curves
These curves can be very hard to read, due to the many cells in one chart. When in doubt about which cell a specific curve is, use the charts under each cell to confirm the cell type.
0.2 ampere discharge
0.5 ampere discharge
1 ampere discharge
2 ampere discharge
5 ampere discharge
Not all batteries can sustain 5 ampere discharge and few batteries are rated for it. Because some curves are missing the color of the curves are different from above.
Curves and pictures for each cell
The individual curves are here
For all battery types I have tested two different cells, they are called A and B in the graphs. All cells have been charged on a hobby charger with half the marked capacity as charge current and the charge is stopped when the current is 1/10 of the charge current. I.e. if the battery is marked 3000mAh it is charged with 1500mA and the charge is stopped when the current is down to 150mA. (Note: For Samsung at 4.35 volt I used another charger).
This charge method will not reach the maximum capacity of the batteries, there might be space for a few mAh more. Batteries that are marked with too high capacity will be penalized with this charging method.
When I only use one curve for a battery, it is the curve from battery A.
All the discharging is done on a CBA and I frequently verify that the reading from the CBA matches readings taking with a voltmeter directly over the cell.
Both capacity and energy is done in one discharge, capacity is a summation of the current, energy is a summation of current*voltage.
Cytac batteries were supplied by Cytac for a review.