18650 Battery Tester by Rick England, KC6UFT
We featured an interview with Rick on the HRWB episode 176. In that episode, Rick described the
18650 battery tester he was designing. The tester is a dynamic DC load tester. It simply applies three,
timed progressively increasing resistive loads to the battery under test and calculates the cells internal
resistance. The DC method was selected over the faster and simpler AC impedance measurement
because it is more consistent and more closely represents the loads encountered in most DC
applications. Over the last year much progress has been made and the features of the tester have
expanded beyond the initial concept. The tester reports back detailed measurements (Voltage, Current,
Voltage Drop, etc.) via LCD display as well as simple pass/fail indications (9 states) using 5 on-board
LEDs.
Rick is featured in episode 218 where he talks about the design and the future direction of the project.
Here are pictures of the latest version of the battery tester.
18650 battery tester he was designing. The tester is a dynamic DC load tester. It simply applies three,
timed progressively increasing resistive loads to the battery under test and calculates the cells internal
resistance. The DC method was selected over the faster and simpler AC impedance measurement
because it is more consistent and more closely represents the loads encountered in most DC
applications. Over the last year much progress has been made and the features of the tester have
expanded beyond the initial concept. The tester reports back detailed measurements (Voltage, Current,
Voltage Drop, etc.) via LCD display as well as simple pass/fail indications (9 states) using 5 on-board
LEDs.
Rick is featured in episode 218 where he talks about the design and the future direction of the project.
Here are pictures of the latest version of the battery tester.
Testing a SCUBA diving flashlight: Having your dive light fail on a night dive can leave you in the dark.
“Hmm.. I fully charged it up last year and I charged it last night… the charger said it was “Full”? Lithium-
ion batteries naturally degrade over time. Degradation rates are higher when Li-Ion batteries are stored
at full charge. Storing at full charge lead to significant losses in cycles and usable capacity.
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Testing a LiPo flat pack: Search Amazon for “small 3.7v lipo” and you’ll see “1-48 of over 2,000 results”.
LiPo flat packs are in everything these days.. From TinyWhoop RC drones to micro RC helicopters; From
electronic shifting, radar and bike computers on bicycles to even being the sole source of power
(receiver, telemetry, servos, etc) for RC Carbon fiber Discus Launch Gliders which are only manufactured
in the Ukraine! Having a $3.00 cell fail on a $1300 glider means loosing it. When your shifter battery
goes dead on a bike ride, your stuck in that gear for the rest of your ride.
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Testing 18650 Cells using the 4-wire method. An 18650 (or a 21700, 18350, etc.) battery is tested using
three precisely timed load conditions. The adjustable 4-wire fixture (Thank you Marcel) permits more
accurate IR calculations than a two wire method. Either can be used. The cell’s internal resistance is
calculated for each test and displayed on the LCD. At the end of each test the tester indicates the
batteries “fitness” using the colored LEDs. This picture shows 1 of 5 cells being tested from a Ryobi Tool
Battery pack testing “GOOD”- Note a simple green LED indicating the cells fitnes, as well as the test
summary test results (internal resistance and cell voltage).
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An 18650 (or a 21700, 18350, etc.) battery is tested using three precisely timed load conditions. The cell’s internal resistance is calculated for each of three progressively higher load tests. The test results are displayed on the LCD. A colored LED is a simple indicator for the batteries “fitness”. In this case the cell tests POOR/BAD. Time to retire and recycle this cell. |
FEATURES
USE CASES
SUPPORTED BATTERIES
METHOD
OBSERVED
- 9 levels of battery health on 5 LEDs
- Voltage, Voltage-drop, current and internal resistance are displayed on the LCD
- 2-wire or 4-Wire testing for more accurate IR measurements
- Load resistors can be fixed (solder) or use plugs to quickly change load resistances
- Simple standalone testing and measurement or use with a computer for detailed test logs
- Single cell testing of 18650, 21700, 26650 and lightweight LiPo cells used in RC and drone
- applications
USE CASES
- Test newly purchase cells for quality and consistency
- Sort cells by internal resistance for use in series or balanced storage banks
- Debug “dead” battery packs that will not accept a charge. Identify bad cells within the pack
- Identify problems like frayed, broken lead wires
- Characterize the fitness of cells for critical applications(Diving, Flying, Navigating, etc)
SUPPORTED BATTERIES
- Li-ion 18650, 26650, 21700, 18350, etc cells
- LiPo pouch cells
- LiFEPO4 26650 cells
METHOD
- Charge (or discharge) the cell to nominal voltage (3.7V)
- Measure cell’s internal resistance (IR…measure the battery impedance at 3.7V (nominal) using DC load test.)
- If cell tests good or better, perform capacity test by performing a full charge and discharge cycle.
OBSERVED
- Cells get “lazy” (IR declines) if left unused. Then “recover” somewhat when placed in service
- Fully charged cells (Voltage) is not an indicator of battery fitness
- Cell capacity is not an indicator of battery fitness
- 18650 cells (5) in series (20v tool packs) will not accept a charge when one of the cells is discharged. If the pack is opened and re-balanced, it will continue to deteriorate if cells have mismatched IR’s
Flex Radio Announces New Radios: 8400 / 8400M / 8600 / 8600M
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Flex Radio 8000 Series Press Release
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Flex Radio 8400 Series Brochure
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Flex Radio 8600 Series Brochures
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Flex Radio Maestro C Remote Control Head
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Multi-Meters - Dr. Doug Millar K6JEY
In episode 208, Doug tells us all about the wide world of modern multimeters.
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Presentation: Modern Multimeters by Doug K6JEY
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All About HF Wattmeters - Dr. Doug Millar K6JEY
In this episode 137, Doug walks us through all the ins and out of RF watt meters. How they are designed, how they work, what their limitations are and what is special about various models.
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Presentation: All About HF Wattmeters by Doug K6JEY
Article: How SWR Meters Work by Glen W9IQ
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Station Switch Box Project - Vince VE6LK
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In episode 130, Vince talked about his station switch box project. Here is the schematic for that project.
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Receiver Optimization
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Earth - Moon - Earth and 10 GHz Operating - Dr. Doug Millar K6JEY
Episode 111
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Sidewalk 10 GHz EME
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Sidewalk EME
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Doug K6JEY's Lab
Doug K6JEY at the classic station operating position
Test Gear For Ham - Dr. Doug Millar K6JEY
Episode 109
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Test Gear For Hams
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