MFCC Battery Charger Test Report
Jason Owens
February 27, 2013
#042
ABSTRACT
This report discusses the results of a set of comparison tests between the Multi-Function
Charge Controller (MFCC) pulsed battery charger and the E-Z-GO 36 V, 16 A DC charger.
The input electrical power draw of each battery charger was compared, along with the
charging time, and effect on a bank of 36V Trojan T105 golf cart batteries to determine
which charger had the best overall performance.
i
CONTENTS
Abstract .............................................................................................................................................................................. i
List of Figures ............................................................................................................................................................... iii
List of Tables ................................................................................................................................................................. iv
1.
2.
3.
4.
Introduction ...........................................................................................................................................................1
1.1
Background ...............................................................................................................................................1
1.2
Purpose .......................................................................................................................................................1
1.3
Scope ............................................................................................................................................................1
1.4
Test Setup...................................................................................................................................................2
Methods, Assumptions, and Procedures ..................................................................................................6
2.1
General Testing Procedure ................................................................................................................6
2.2
Measurement Methods ........................................................................................................................7
Results and Discussion .....................................................................................................................................9
3.1
AC Input Voltage, Current, and Power Waveforms ................................................................9
3.2
Data Summary ...................................................................................................................................... 12
3.3
Discussion ............................................................................................................................................... 13
Conclusion............................................................................................................................................................ 14
References ..................................................................................................................................................................... 15
Glossary .......................................................................................................................................................................... 16
ii
LIST OF FIGURES
Figure 1 – Battery Charger Test Stand ...............................................................................................................2
Figure 2 – Battery Test Stand Diagram ..............................................................................................................3
Figure 3 – Battery Bank and Load Resistors....................................................................................................4
Figure 4 – Programmable Relay Module ...........................................................................................................4
Figure 5 – DC Charger Status LED Detector Circuit......................................................................................5
Figure 6 – 50 Amp Current Sensor Module ......................................................................................................7
Figure 7 – Current Sensor Enclosure ..................................................................................................................7
Figure 8 – Test Status Page ......................................................................................................................................8
Figure 9 – Data Plot Page ..........................................................................................................................................8
Figure 10 – MFCC Pulse Charger Input Current and Voltage ...............................................................9
Figure 11 – MFCC Pulse Charger Input Power Waveform ................................................................. 10
Figure 12 – MFCC Pulse Charger Average Input Power over Time ............................................... 10
Figure 13 – E-Z-GO DC Charger Input Current and Voltage .................................................................. 11
Figure 14 – E-Z-GO DC Charger Input Power Waveform........................................................................ 11
Figure 15 – E-Z-GO DC Charger Average Input Power over Time ...................................................... 12
iii
LIST OF TABLES
Table 1 – MFCC Pulse Charger Statistics ..................................................................................................... 12
Table 2 – E-Z-GO DC Charger Statistics ........................................................................................................... 13
Table 3 – Battery Charger Efficiency Comparison ..................................................................................... 13
iv
1.
INTRODUCTION
1.1
Background
The technique of pulse charging batteries is a relatively new concept. Most standard
charging systems, such as the E-Z-GO utilize DC power to charge batteries. However, pulse
charging techniques are claimed to enhance the performance and longevity of a battery
because of the pulse’s ability to desulfate the battery simultaneously while it is being
charged. Other observed effects of pulse charging have included increased energy storage
capacity for a given battery size, and increased cycle life. The MFCC Charger is one of
these pulsed systems and is claimed to exhibit similar characteristics. [1]
1.2
Purpose
The purpose of this investigation is to determine and compare the efficiency of the MFCC
Battery Charger to the E-Z-GO Powerwise QE 16A DC charger; the end goal being to verify
the claim that the MFCC Charger uses 90% less power than the DC charger.
1.3
Scope
This claim was evaluated by preparing a test stand capable of monitoring the real-time
power input and output of each charging system during the charging process. The AC input
voltage and current was monitored using an oscilloscope, equipped with voltage and
current probes, to log the AC input waveforms throughout the charging process.
The batteries used in the test were Trojan T105 6 V golf cart batteries, arranged in two
36 V banks, one for each charger. The batteries then underwent a discharge cycle after each
charge cycle, so that the energy stored in the battery bank can be tested. During this
process, the voltage across each battery bank was monitored to ensure that the batteries
were discharged consistently to the same level in both trials.
1
1.4
Test Setup
Figure 1 – Battery Charger Test Stand
The battery charger test stand consisted of a Velleman PCSGU250 12 MHz PC Oscilloscope,
which was used to monitor and record the input and output voltage and current
waveforms. CH1 of the oscilloscope was used to monitor the AC input voltage to each
charger while CH2 was connected to a magnetic Hall Effect sensor to monitor the line
current. A Kill-A-Watt Wattmeter was used as a secondary measurement source to
monitor and verify the battery chargers’ input power consumption.
2
Figure 2 – Battery Test Stand Diagram
A set of parallel 1 Ohm, 2500 W, load resistors were connected to the test stand through a
100A contactor, which was used to discharge the test battery bank to ensure that both
banks were at the same charge before beginning data collection. The load bank was used
again after the charging cycle to record and determine the amount of stored energy in each
battery bank.
3
Figure 3 – Battery Bank and Load Resistors
The load bank was designed to draw a nominal current of 75 A at 37.5 V, to simulate a golf
cart driving on flat terrain. The 75 A current value was determined from measurements
given by the client for the above driving conditions.
Figure 4 – Programmable Relay Module
To control each of the hardware components, a computer programmable 4-channel relay module
was used, with one channel to connect the battery chargers to the wall outlet, one channel to
4
activate the 100 Amp contactor for the load bank, and one channel to control the cooling fan for
the load bank.
A PC software program was written to handle communications between the oscilloscope
and the relay board to take measurements. Input and output waveform data was collected
every 500 milliseconds to calculate the instantaneous power and overall energy input for
each charger. These calculated values, along with the raw waveform data, were datestamped and logged for later review and analysis.
To monitor the status of the MFCC Charger, a serial cable was connected to the charger’s
RS232 port to feed status information to the PC software. When the status information
indicated that the charge cycle was completed, the software automatically switched the
system into the discharge cycle. However, the E-Z-GO charger was not equipped with this
feature. The only indication of charge status was a single LED, which blinked during the
charging process, and stayed on continuously when charging was completed. In order to
interface this to the PC program, a small breadboard circuit was constructed, equipped
with a photo-resistor to convert the blinking LED into a digital signal which could be
monitored by the system control software via the serial port. In this way, the software
program could also automatically switch to the discharge cycle once the DC charger
completed its charge cycle.
Figure 5 – DC Charger Status LED Detector Circuit
5
The data which was collected for each battery charger is as follows:
1.
AC Input Voltage
2.
AC Input Current
3.
Charger Status Information
The data which was derived from the raw measurements is as follows:
1.
AC Input Power
2.
Average Input Power over Charge cycle.
3.
Total Kilowatt-hours of input energy over charge cycle.
4.
Data comparison of the Pulse and DC charger performance
2.
METHODS, ASSUMPTIONS, AND PROCEDURES
2.1
General Testing Procedure
To complete the testing for each charger, the following procedure was implemented:
1.
Connect the twelve test batteries into two banks of six, 36 V sets to use for each
charger.
2.
Connect the first bank to the test stand to pre-charge the batteries using the MFCC
Battery charger without collecting data.
3.
Pre-Discharge the bank using the 0.5 Ohm, 5000 W load bank for a period of 15
minutes while monitoring the bank voltage to ensure the batteries are in a known
state of charge.
4.
Connect the MFCC Battery Charger to the test bank and begin the charging
process. Parameters to be monitored are the input AC voltage and current, and
5.
charger status information from the MFCC battery charger’s serial port.
Once the charging cycle is complete, discharge the battery bank using the 0.5 Ohm,
5000 W load bank for 15 minutes while monitoring the battery voltage.
6.
Recharge the battery bank again, according to the procedure outlined in step 4,
completing a total of four charge-discharge cycles.
6
7.
Connect test bank 2 to the test stand and pre-charge the batteries using the E-Z-GO
DC battery charger without collecting data.
8.
Pre-Discharge the bank using the 0.5 Ohm, 5000 W load bank for a period of 15
minutes while monitoring the bank voltage to ensure the batteries are in a known
state of charge.
9.
Connect the E-Z-GO DC charger to the test bank and begin the charging process.
Parameters to be monitored are the input AC voltage and current, and charger
status information from the status LED, using the photo detector circuit.
10.
Once the charging cycle is complete, discharge the battery bank using the 0.5 Ohm,
5000 W load bank for 15 minutes while monitoring the battery voltage.
11.
Recharge the battery bank again, according to the procedure outlined in step 9,
completing a total of four charge-discharge cycles.
12.
Once the test is completed, process all input and output waveforms to determine the
average power and total watt-hours of input energy consumed by each battery
charger.
2.2
Measurement Methods
The AC input current measurements were taken using a CS-50A Hall Effect current sensor
module sold by Panucatt Devices. The current sensor module features the ACS758 Hall
Effect current sensor manufactured by Allegro Microsystems. It is an AC/DC current sensor
with a measurement range of ± 50 Amperes and a maximum bandwidth of 120 kHz.
Figure 6 – 50 Amp Current Sensor Module
Figure 7 – Current Sensor Enclosure
7
This current sensor module was then fitted into a custom enclosure equipped with plugs to
connect between the battery charger and AC outlet. The sensor, which requires a 5V DC
supply, was connected to a Grundig programmable DC bench top power supply. The 120V
AC voltage was measured using a 100x oscilloscope probe, connected to the AC and neutral
voltage output connections on the current sensor box. A 10 nF capacitor was connected
between the neutral line and the oscilloscope probe ground to prevent any potential
ground loop currents from entering the oscilloscope.
The custom-made computer software was designed to not only control the test setup
hardware, but also collect and process the raw input data in real time during the charge
cycle.
Figure 8 – Test Status Page
Figure 9 – Data Plot Page
The software, after reading the raw AC current and voltage screenshots from the Velleman
oscilloscope, would calculate the instantaneous AC power waveform, and determine the
average power over the time interval of the data capture. The average power is then used
to determine the number of joules of input energy during the time interval, which is then
summed over the entire charge cycle to determine the total kilowatt-hours of energy input.
This information would then be plotted on the interface and stored in data files on the
8
computer’s hard drive for later analysis if necessary. Details of the collected data are shown
in the next section.
3.
RESULTS AND DISCUSSION
3.1
AC Input Voltage, Current, and Power Waveforms
200
4
150
3
100
2
50
1
0
0
0
0.1
0.2
0.3
0.4
0.5
-50
-1
-100
-2
-150
-3
-200
Time (Seconds)
-4
Voltage
Figure 10 – MFCC Pulse Charger Input Current and Voltage
9
Current
Input Current (A)
Input Voltage (V)
Below are characteristic plots of the AC waveforms for the MFCC Pulsed Battery Charger:
500
400
Input Power (W)
300
200
100
0
-100
0
0.1
0.2
0.3
0.4
0.5
-200
-300
-400
-500
Time (Seconds)
Figure 11 – MFCC Pulse Charger Input Power Waveform
The following plot shows the average input power over the entire charge cycle of the
battery bank:
160
Input Power (W)
140
120
100
80
60
40
20
0
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
Time (Hours)
Figure 12 – MFCC Pulse Charger Average Input Power over Time
10
9:00
Input Voltage (V)
The next set of plots depict the typical AC waveforms for the E-Z-GO DC battery charger
200
8
150
6
100
4
50
2
0
0
0
0.1
0.2
0.3
0.4
0.5
-50
-2
-100
-4
-150
-6
-200
Time (Seconds)
-8
Voltage
Current
Figure 13 – E-Z-GO DC Charger Input Current and Voltage
1000
Input Power (W)
800
600
400
200
0
0
-200
0.1
0.2
0.3
0.4
Time (Seconds)
Figure 14 – E-Z-GO DC Charger Input Power Waveform
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0.5
The following plot shows the average input power over the entire charge cycle of the
battery bank:
900
800
Input Power (W)
700
600
500
400
300
200
100
0
0:00
0:30
1:00
1:30
2:00
2:30
3:00
Time (Hours)
Figure 15 – E-Z-GO DC Charger Average Input Power over Time
3.2
Data Summary
Tables 1 and 2 show the summary statistics for the above plots.
Table 1 – MFCC Pulse Charger Statistics
Trial
1
Average Power (W)
111.90
Total Energy (kWh)
0.957
Time (h:mm:ss)
8:33:31
2
3
111.64
111.76
0.974
0.982
8:43:28
8:47:31
4
Average
111.67
111.74
0.978
0.973
8:45:34
8:42:31
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Table 2 – E-Z-GO DC Charger Statistics
Trial
Average Power (W)
Total Energy (kWh)
Time (h:mm:ss)
1
2
485.66
485.98
1.495
1.501
3:04:41
3:05:20
3
4
Average
485.16
491.96
487.19
1.499
1.503
1.499
3:05:22
3:03:19
3:04:41
Lastly, the overall efficiency comparisons between the two chargers are shown in Table 3
below.
Table 3 – Battery Charger Efficiency Comparison
3.3
Instantaneous Power Ratio (Pulse/DC)
22.94%
Energy Efficiency (Pulse/DC)
DC Charger Peak Power (W)
64.89%
804.36
Pulse Charger Peak Power (W)
147.10
Discussion
The Instantaneous power ratio is the ratio of the pulse charger’s average power to the DC
charger’s average power. This statistic states that the pulse charger, on average, uses
22.94% of the power that the DC charger uses during a given charge cycle. The Energy
efficiency is comparing the kWh of energy used by the pulse charger to that of the DC
charger. This statistic states that overall, the pulse charger uses 64.89% of the energy that
the DC charger uses to supply the same amount of energy to the battery bank.
While the Pulse charger’s energy efficiency is only 35.11% more efficient than the DC
charger, its charging characteristics still make it more ideal of a charger compared to the EZ-GO. As can be seen from the data, the DC charger actually charged the batteries in a little
over 3 hours, compared to the 8 hours of the pulse charger. However, during the charge
cycle of the DC charger, the golf cart batteries vented significant amounts of battery acid
into the air, meaning that the battery acid was slowly being boiled away. However, the
Pulse charger did not have this effect on the batteries at all. They didn’t need any significant
ventilation and the batteries themselves remained cool throughout the cycle. This means
that overall battery health and maintenance is significantly improved with the use of the
pulse charger, in addition to the electrical energy savings.
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4.
CONCLUSION
Based on the data collected, the MFCC battery charger appears to be an overall superior
system for charging and maintaining 36V battery banks. Though it requires extra time to
recharge the batteries, the advantages of increased battery lifetime, energy efficiency, and
health/safety through minimizing battery outgassing, easily offset this minor
inconvenience. Additionally, the charger’s ability to output the charging statistics via its
serial port add another dimension of flexibility, which not only made it easier to conduct
this investigation, but serves as a good monitor for overall battery health over time.
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REFERENCES
[1] J. Owens, “MFCC Battery Restoration System Test Report,” Resonance Group.,
Toledo, Ohio. Rep. 41, 2012.
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GLOSSARY
Ampere-Hour (Ah)
A measure of the charge storage capability of a battery,
equal to 3600 Columbs of charge. This quantity
indicates the amount of energy the battery can deliver
at its rated voltage for 1 hour. However, in practice, this
value varies depending on the discharge rate of the
battery due to the effect of Peukert’s Law. [1]
Average Power (W)
Equal to the DC equivalent value of an AC power
waveform averaged over a given time interval.
Instantaneous Power (W)
Equal to the instantaneous voltage multiplied by the
instantaneous current flow in an electrical system.
Kilowatt Hour (kWh)
A unit of work (energy) equal to 1000 Watts of power
dissipated over one hour’s time.
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