Feasibility Testing Report – Battery Capacity Test

Feasibility Testing Report – Battery Capacity Test
Feasibility Testing Report – Battery Capacity Test
Team: P15001: Active Ankle Foot Orthotic
Engineers: Megan Ehrhart – Electrical Engineer
Jared Green- Mechanical Engineer
Test Date: 03/12/2015
Related System: Recharge or Replace Battery (ADB)
The test is being completed to determine how long the battery can last on a typical days
use before having to be recharged. It also helps determine how much maximum current
will be drawn to prevent any short circuits from occurring. Both these outcomes are
based on a typical days use whether a test subject is using this device in active or idle
mode.
Supplies:
1.)
2.)
3.)
4.)
5.)
AFO control device
1 ohm high power resistor
Data logger
Oscilloscope software
9v battery
Setup:
1)
2)
Connect the output of the power source to the 1 ohm resistor
Connect each end of the resistor to the Data logger so that voltage drop across the
resistor can be recorded
2)
Connect the data logger to a laptop where the outcome and run the oscilloscope
software
Procedure(s):
Test:
1. Turn on the AFO and run the device in active mode and compress the heelstrike
compression sensor to represent a typical gait cycle.
2. Save the data obtained
3. Repeat the procedure in idol mode, no compression is necessary
4. Save the data obtained
Data Analysis:
1. Using ohms law across the 1 ohm resistor can determine current drawn
P15001: Active Ankle Foot Orthotic - Updated on March 18, 2015
2. Using the power rating on the 9v battery as well as an expected amount of time
someone could use in either mode, total usage of this device is recorded.
Results:
Figure 1: The following plot displays the raw data which represents amount of current that is drawn when the
dive is being used in active mode. Each spike represents heel strike
Figure 2: The following plot displays the raw data of current drawn when the device is in idle mode. No steps
taken
P15001: Active Ankle Foot Orthotic - Updated on March 18, 2015
Time calculations
Battery active (hrs)
Battery idle (hrs)
4.46
8.9
Geni sec/step
Expected sec/step
1.35
2.7
Total expected steps
1500
Expected active time (sec)
Expected active time (hr)
4050
1.125
Expected total use (hr)
Percent use in idle
Expected idle time (hr)
Total use (hrs)
8
25%
6.655
7.780
Figure 3: The following table displays steps for determining the total usage on a particular day
ER9: Max current (mA)
Ideal Value:
100
Marginal Value:
200
Obtained value
95
ER10 Time between charges (hours)
Ideal Value:
8
Marginal Value:
6
Obtained value:
7.78
Figure 4: The following table compares results obtained from the test to the engineering requirements
Conclusion:
From testing the battery, maximum current does not go above ideal value and the time
between charges is above marginal value. As a result, this device can last for a full days
use before a charge is necessary.
P15001: Active Ankle Foot Orthotic - Updated on March 18, 2015
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