Transcript Year 5 - helping with technology transfer

Field Sustainment Power Conditioning
#TA3-04-5 (Solar Battery Chargers)
Brad Lehman, Northeastern University
Khalil Shujaee, Clark Atlanta University
Wes Tipton, Army Research Laboratory
George Frazier, SAIC (Year 5 - helping with technology transfer)
Presentors: Khalil Shujaee (CAU) and Florent Boico (NU)
Presented at CTA Conference:
June 2, 2005
Motivation/Background
•
Background
– Dept. Army recently mandated that all training exercises must use
rechargeable batteries;
– Estimated to save $70M annually (versus non-rechargeable);
– About 75% of Army rechargeable batteries are BB390 NiMH (4lbs). (BB390 has
2 x 12V legs and can be used as either 24V or 12V battery.)
•
Motivation for Solar Chargers
– Soldiers carry four BB390 batteries
(= 16 lbs) for portable electronic
equipment;
– Forward field observers, scouts,
special ops, are constrained to stay
within 10 miles of TOC (Tactical
Operation Center where there is a
charging facility shelter);
– Portable solar arrays carried by
soldier (~1lb) reduce number of
batteries carried and eliminate the
need to stay near TOC.
Operation area
10 mi.
Soldiers using batteries
TOC
Spare batteries, generator ,
Chargers, shelter, etc.
Solar Charging BB390
11:15am
11:15am
I I2
–
–
–
–
I1
11:00am
V
V2
V1
11:00am
Companies have attempted to work with CERDEC to build NiMH solar chargers:
• Chargers failed: They falsely terminate charging before completion;
• CERDEC refused to use any of these chargers. BUT batteries become damaged or have
reported reduced life-cycle when connecting directly to the solar array.
Known charging algorithms are applicable to constant power source:
• Termination for “dumb” NiMH batteries (BB390) occurs based on battery V, dV/dt, time,
and sometimes temperature T or dT/dt.
Solar arrays produce varying current sources depending on clouds (fools known chargers)
• Fast charge
Slow charge
Fast charge …
How to correctly predict charge termination for DUMB batteries like BB390 (basic research)?
Summary: Research Outcomes
Prototype
Charger
Prototype
BB390
leg1
leg2
voltage
leg 1&2
Battery
thermistors
leg1
leg2
ADC
PIC µC
charging current
Major Accomplishments:
 Explained that performance degradation of
batteries when charging with solar array is due to
high temperature overcharging;
 Designed, built and tested Phase I solar array
NiMH battery charger control algorithms;
w Over 50 experiments: 0% failure rate!!
w Preliminary patent disclosure
 Maximum Power Point Tracker (Phase II) charger forces solar array to produce more power;
 2005 IEEE PESC paper to appear in June.
Must Be Sure Algorithm:
• Immune to changing illumination or temperature
conditions
• Permits a little overcharging to « make sure »
battery is full SOC
Hardware:
 Monitors voltage, current and temperature for
each leg (thermistors inside BB390)
 Differential temperature measurements
between battery legs determine when charge is
complete.
Phase II: Maximum Power Point Tracking (MPPT)
Bypass
switch
Iout
Up-Down
converter
PV array
We have built preliminary Phase II chargers
that include MPPT:
d
DPWM ADC
µ controller
filter
Current
Sensing
resistor
• Adjusting the duty ratio of the Up-Down
converter forces the solar array to operate at its
maximum producing power point;
• MPPT adaptively optimize charging to
different NiMH batteries (12V, 24V, 9.6V, etc.)
• Bypass switch improves power efficiency
when MPPT not needed.
Higher Charging Current is Achieved with MPPT
Battery
Voltage
Current when solar array is directly
connected to the battery
Current when the proposed charger
with MPPT is used.
4.8V
660 mA
720 mA
12V
310 mA
310 mA
24V
0 mA
160 mA
Relevance to Army’s Vision
• Army Future Force Warrior (FFW)
– Power Vision: “72-hour continuous autonomous
team operations, high density, low weight/volume, selfgenerating/re-generating, reliable, safe power
source/system.” (from FFW home web page)
US Army Natick Research Center vision of
what a FFW in 2020 (left) and 2010 (right)
will look like
•
Roadmap/Relevance of Research to FFW
1.
2.
Our proposed solar battery chargers are lightweight, use renewable
energy, are reliable quiet: Directly impact FFW power requirements.
We are attempting to transition technology developed:
–
–
–
3.
Year 6 – 8 outcomes hope to provide great flexibility to the soldier:
i.
ii.
4.
Negotiating with vendors to implement the algorithms on their existing chargers;
Discussing with CERDEC on “convincing” their vendors to use new algorithms;
Two recent meetings with US Army Natick Research Center (they seem to deal with
larger (kW) power systems, but have been open to discuss new projects)
Develop charger that can utilize various input power sources (from solar to wind)
Ability to recharge any battery chemistry type, such as Li-ion, NiMH, NiCd.
Potential commercial, dual-use, technology transfer to portable solar
battery chargers for campers, RV’s, etc.
Proposed Research Activity For Year 6-8
VISION: Design and build a smart Future Force Warrior power
system architecture capable of:
• Sensing and adapting charge algorithms according to battery chemistry
• Running from primary source, rechargeable battery or from combination thereof
• Ability to recharge battery with virtually any primary source (AC, DC, solar wind, etc.)
• Programmable output voltage.
• Handling input voltage range of up to 5:1
Isolated Push-Pull
Microcontroller
Source 3:
Rechargeable
Battery
(hot-swappable)
BatteryEnable
Bus-V/I
Bus-Enable
Bat V/I
SMBClock
SMB Data
Bat-Temp
Bat-V
Charging-Enable
A vision of a Future Force Warrior
power system architecture
CC V/I
AC-good
prim-good
V/I control
AC/DC
Source 1:
AC Mains
90V~240V
DC-DC
Converter 1
Load 1
DC-DC
Converter n
Load n
SW2
SW1
Up-Down
Charger /
Converter
Source 2:
Primary DC
Source
10V~48V
SW3
Intermediate
Power Bus
(10V~28V)
Appendix
• Supporting slides for presentation that will not be
shown in the limited 10 minute presentation
Roadmap YEAR 4-5
YEAR 4
YEAR 5
Generalization to AA
& Other Battery Types
(Beginning of the Project)
Technology Transfer
New
NiMH
Algorithm
STO/RDECOM
Solar Panel
Layout Optimization
Lab Prototype
of BB390 Charger
YEAR 4 Achievements:
•
•
Field Testable
Prototypes
Field
Testing
(CERDEC)
Designed a robust solar NiMH battery charge control algorithm.
Built charge controller that clamps onto BB390 with embedded algorithm.
YEAR 5 Expectations/Objectives:
•
•
•
Transfer charger algorithms to existing CERDEC vendors to implement within their
BB390 chargers: target timeframe to achieve this is by the end of GFY 2005.
Conduct field testing of the prototypes.
Technology Transition:
-
Extend algorithm to other NiMH batteries, e.g., commercial AA cells
STO program: Help optimize layout of solar cells in for applications at US Army Natick
Soldier Center.