Building a Lithium Cell Capacity Tester

Published  May 30, 2023   
Aswinth Raj


From a simple hand-held trimmer to a super-fast electric car, Lithium batteries have found their way into a lot of applications in recent times. The voltage of a single lithium cell normally varies between 3.2V to 4.2V, and is combined to form a battery pack that can provide higher voltage and capacity. While the process seems to be pretty simple, things get pretty complicated when the number of cells used in a battery pack increases, mainly because each cell used in the battery pack should have the same capacity and similar IR (Internal Resistance).

To filter out defective cells and prevent them from getting into a battery pack, manufacturers do something called “Cell Grading”. Wherein each cell is charged to its maximum voltage and then discharged at a constant current to calculate the actual capacity of the cell. Apart from this some Cell Grading machines will also measure the IR and temperature characteristics of the cell during the charging and discharging process. With this data, cells of similar capacity and IR are combined to gather and cells with lower capacity are rejected.

In this video we are building and demonstrating a basic single-cell Lithium Cell Capacity Tester which will be used to measure the capacity of a single cell.

Code File

PCB Gerber File

Components Required

Value Manufacturer Digikey Part Number Datasheet Link    Quantity
0.1uf Samsung Electro-Mechanics 1276-1935-1-ND   Datasheet 20
220uF Würth Elektronik 732-8997-1-ND   Datasheet 2
10uF Murata Electronics 490-GRM188R6YA106MA73JCT-ND   Datasheet 2
18pF KEMET 399-C0603C180K4HAC7867CT-ND   Datasheet 4
LED BLUE Harvatek Corporation 3147-B1931NB--20C007614U1930CT-ND   Datasheet 2
LED RED Harvatek Corporation 3147-B1911USD-20D000114U1930CT-ND   Datasheet 2
SS34 Comchip Technology 641-2115-1-ND   Datasheet 4
MAX1898EUB42+T Analog Devices Inc./Maxim Integrated MAX1898EUB42+TCT-ND   Datasheet 2
ICSP Adam Tech 2057-PH2-06-UA-ND   Datasheet 2
USB_B_Micro Molex WM1399CT-ND   Datasheet 2
Conn_01x02_Female Adam Tech 2057-EBA-02-D-BU-01-ND   Datasheet 2
AO3401A Alpha & Omega Semiconductor Inc. 785-1001-1-ND   Datasheet 2
IRF540N Vishay Siliconix IRF540PBF-ND   Datasheet 2
10K Stackpole Electronics Inc RNCP0603FTD10K0CT-ND   Datasheet 24
1M Walsin Technology Corporation 1292-WR06X105JTLCT-ND   Datasheet 2
1k Stackpole Electronics Inc RNCP0603FTD1K00CT-ND   Datasheet 2
1R/10W TE Connectivity Passive Product A102112-ND   Datasheet 2
1.4K YAGEO 311-1.40KHRCT-ND   Datasheet 2
SW_SPST C&K CKN10880CT-ND   Datasheet 6
LM4041DIM3-1.2+T Analog Devices Inc./Maxim Integrated LM4041DIM3-1.2+TCT-ND   Datasheet 4
ATmega328P-A Microchip Technology ATMEGA328P-AU-ND   Datasheet 2
AD8542 Analog Devices Inc. AD8542ARZ-REELCT-ND   Datasheet 2
16MHZ YIC 3155-16M18PX/XT324-10/10CT-ND   Datasheet 2