# Battery test methodology

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This page contains all the details about how lipo batteries are tested. It is meant for those of you, who want to know exactly what is going on and how values are recorded and analyzed. You don’t need to read this, if you are only interested in how a certain battery performed.

Testing is split in multiple different steps. This methodology overview will follow the same structure as you are used from the battery review.

## Break-in period / Charging

Battery Charger: Junsi 406 DUO with USB connection and live-logging into LogView (Refresh rate 0.5 Hz).

• Charging profile: Balanced Charge, CC/CV. CV phase ends when max. cell drift is 5 mV.

ISR-tester for break-in: Junsi 406 DUO. IR tested after full charge and battery has been heated to reference temperature of around 40 °C.

Discharge: Electronic Load Zentro-Elektrik ELA 1500 in constant current mode.

• Discharge cut-off: 3,3 V for lowest cell OR 58° C on any temperature probe.
• Controlled by Amtel Mega µ-Processor.
• Live-Logging to LogView (Refresh rate 2 Hz)

## Load Testing

Constant Load

Electronic Load: Zentro-Elektrik ELA 1500 in external program mode.

• Current follows pattern (see below)
• Discharge cut-off: 3,3 V for lowest cell OR 58° C on any temperature probe.
• Controlled by Amtel Mega µ-Processor.
• Live-Logging to LogView (Refresh rate 2 Hz)
• Used capacity: Calculated based on current.

Follows pattern of current pulses that are applied for time intervals >= 10 seconds. Base load is 10 C.

Pattern: 10 sec. : 0C — 40 s : 10 C — 10 s : 50 C — 40 s : 10 C — 15 s : 35 C — 40 s : 10 C — 20 s : 20 C — 40 s : 10 C — 15 s : 30 C — 10 C to end

IR measurement

Internal resistance is calculated from the constant discharge results. IR is calculated for each cell using formula  $$IR_{Cell}=\frac{U_{Pulse_{cell}}-U_{Base_{cell}}}{I_{Pulse}-I_{Base}}$$. As battery temperature is highly correlated to IR and temperature increases with progressing discharge, IR is calculated for all four current pulses and averaged at the end.

Dynamic Load

Electronic Load: Zentro-Elektrik ELA 1500 in external program mode.

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• Current follows simulation pattern extracted from real-world telemetry logs.
• Discharge cut-off: 3,3 V for lowest cell OR 58° C on any temperature probe.
• Controlled by Amtel Mega µ-Processor.
• Live-Logging to LogView (Refresh rate 2 Hz)
• Used capacity: Calculated based on current.

Dynamic load testing is done based on two load patterns derived from real world FPV flights. Pattern 1 is a high speed FPV flight around the open field with an average current of around 22 A. Pattern 2 is a freestyle flight around trees in the park with a lot of high current spikes. Average current on this pattern is around 12 A due to more floating periods after full throttle bursts. Patterns are repeated until one of the cut-off criteria is reached.

Utilized Mini Quad Setups

A big thanks goes out to my buddy, Deepimpact.io in Panama for all the data collecting regarding pattern #2! Check out his videos!

 Pattern 1:Fossils Stuff Gravity 280T-Motor MN2206 2000 kVDAL 6040 propsKISS 24a Race Edition ESCKISS FC 32 BitJeti RSAT2 on fully digial Jeti-EX-bus protocollFT951 25 mW VTXRunCam Sky+ 600 TVLNo HD camBattery: Tattu 4S 1800 mAh 75 CAUW: approx 700 grams Pattern 2:ImpulseRC Alien 5″Cobra 2204 2300kvGemfan 5040×3 propsKISS 24a Race Edition ESCKISS FC 32 BitFrSky X4R-SB transmitterFXT799T 200mw VTXHS1177 FPV cameraXiaomi Yi HD cameraBattery: Tattu 4S 1300 mAh 75 CAUW: approx 600 grams

Temperature Measurement

Temperature is measured via 3 digital temperature probes (DS1820). Logging is done aside of all other values like voltages and current. Accuracy of sensors is +/-0.5 °C. Sensors are attached with rubber bands to three different positions on the battery: top, side and near the connection terminal (main power cable).

## Test stand design

For the discharge part a self-developed logging solution is utilized. The core is represented by an Arduino compatible ATMEL MEGA2560 µ-processor. Cell voltage is measured via a high precision 16 bit ADC (TI ADS1115). Voltage is sampled down by four voltage dividers making use of high precision metal film resistors. The electronic load is programmed via a 0 – 10 V control signal representing 0 – 120 Amps of load current. As the ATMEL chip only can output PWM signals up to 5 V a PWM-DA-adapter is used to convert the PWM signal into a 0 – 10 V analog control voltage. Current measurement is done by the electronic load itself. Output and logging is realized using LogView. Once the measurement is completed, export to all common spread sheet formats is possible.

Nils Waldmann

...studierter Wirtschaftsingenieur und Wirtschaftsinformatiker, leidenschaftlicher Modellbauer, Hobby-Fotograf, Akku-Liebhaber und freier Redakteur bei dem Computer-Onlinemagazin Allround-PC.com.