electric fiero lithium
Post on 02-Mar-2022
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The Story Thus Far• Started Conversion of a Pontiac Fiero mid 2007
– Advanced DC 9”, Curtis 144V controller– Maiden voyage 12/2008
• Used Lead Acid Batteries (12*Trojan 30XHS)– Lithium was still expensive; anxious to get started– Range was 18 miles, handling was “heavy”– Batteries were the “weak link”, but there were many areas for
improvement
• Presented to the NBEAA Oct 2009– www.nbeaa.org/presentations/MalloysFieroOct09.ppt
• Daily driver throughout 2009– And then, after 13 months and 2000 miles …
Battery Failure !• Range started dropping
– Range went down to 15 miles or so• Tracked it down to a failing cell under load
– All cells showed the same voltage at rest– But under load, one cell sagged more than others
• And the “self discharge rate” was much higher
• Lithium prices were dropping and decided to upgrade– … and so began Phase II
Outline
• Batteries• Battery Management and Instrumentation• Other Upgrades
– Charger– Control Board– Vacuum Pump– Heater
• Lessons Learned• Scorecard
• Future Projects
Battery Choice
ThunderSky (now Sinopoly) 160Ah
• Thunder Sky 160Ah– Readily available– Installed in “blocks of four”– Size comparison:
• Lithium(x4) = 4 x 10.2 x 11• Lead Acid(x1) = 6.75 x 14 x 10.1
• Decided on a 44 Cell Pack– Have 11 “blocks of four” cells– 4x Lithiums have a slightly higher
nominal voltage than 1x SLA– Wanted to be conservative on max
voltage– In retrospect, 48 cells would have
been fine and would have given more range
Lead Acid Battery Boxes
• Original design was “bolted steel”– Cheap, within my abilities, but far from ideal
Lithium Battery Boxes
• The upgraded design: TIG Welded Aluminium– Bought a welder, learnt from youtube and trial and error– Weight savings total: ~120 lbs
Battery Safety• Layout Notes
– Layout: lowest voltage cell at rear left, highest voltage cell at front right.
– Two contactors, one fuse, one circuit breaker in high current path
– For Lithium, removed the Anderson connectors and added the circuit breaker
• “Battery Box” Construction– Lithium cells came in “packs of four”. Retained original holding plates and straps when possible
– Cell straps and BMS connections covered with plexiglass(gives protection from a “dropped wrench”)
– Lugs feed through plexiglass, connected via jumpers
Lithium vs Lead AcidLead Acid Lithium
Pack 12 * Trojan 30XHS 44 * ThunderSky 160Ah
Cell Dimensions (w*l*h)Cell VolumePack Volume
6.75 x 14 x 10.1954.5 cu in11454 cu in
2.55 x 4 x 11112.2 cu in (224.4)4937 cu in
1/2(X.43)
Cell WeightPack Weight
66 lbs792 lbs
12.3 lbs542 lbs (‐250lbs)
2/3(X.68)
Expected lifetime (# charges) 500 3000 X6
Capacity – ratedCapacity – usable (est)Capacity – pack (est)
72Ah (75A for 57 min)44Ah (est)6.4KwH(11.8V *12*45Ah)
160Ah (480A for 20 min)106Ah (est)15KwH(3.2 * 44 * 106 Ah)
X2.3
Maintenance Monthly Watering n/a
Cost $2,200 $10,000 X4.5
Range went from 18 to 40+ miles
Battery Management Functions• While driving …
1. Measure pack state of charge2. Measure individual cell undervoltage3. Indicators (/ preventative actions) if pack or cell is
undercharged• Idiot light, buzzer, limp‐home mode
• While charging …4. Stop Charger when the Pack is fully charged5. Stop Charger if a single cell gets overcharged
• and6. Cell Balancing (keeping cells in balance)7. Diagnostics (early detection of a failing cell)
Lead Acid Battery Instrumentation
PakTrakr
State of Charge
DC/DC Converter Status
Pack Charge Status
Ammeter
Motor OverTemp
Lithium BMS RequirementsBMS Feature Lead Acid Lithium
Pack SOC YES – Curtis REQUIRED
Cell UV YES – PakTrakr REQUIRED
Idiot LightBuzzerLimp Home
NoNoNo
REQUIREDNice to haveMaybe
Charge TerminationCell Overvoltage
AlgorithmNo. (results in Hydrogen Gas)
REQUIREDREQUIRED
Cell Balancing n/a A strategy is required. Automatic balancing is a nice to have (?)
Diagnostic Basic logging supported but not used
A strategy is required.Manual voltmeter is the fallback.
BMS Requirements for Lead Acid vs Lithium are slightly different.
E‐Xpert Pro
• Single most important gauge– Pack “gas gauge”, voltmeter and ammeter
• Measures: charge‐ and discharge current, consumed amp hours
• Used with 5:1 prescaler– Keeps high voltage out of cabin
• Programmable
Mini BMS• Analog BMS with all the basic features ‐• While driving
– If any cell drops below 2.6v (the Low Voltage Cutoff),– the BMS sounds a buzzer and turns on a dash light
• While charging– If any cell goes over 3.8v (the High Voltage Cutoff),– the BMS stops the charger
• Also supports “Top” balancing– If the cell goes over 3.7v (the “Shunt Voltage Threshold”), the shunt
resistor is enabled (current is ~750ma) The benefits of Top Balancing are controversial
• And supports “Limp home” mode– The BMS Master can control the accelerator potbox But this was not used
Mini BMS ‐ Installed
• Grouped the remotes rather than place them directly above a cell
• Easier to see the state of the pack
• “Spaghetti wiring”• Mixed feelings about the results
Charger• Wanted a 110V “opportunity” charger
– Had a 220V onboard charger– 220v plugs weren’t standardized; always charged “at home”
• Removed the Zivan NG3, added an ElCon PFC 1500– Supports both 110 / 220– Has BMS integration with “charge enable” contacts
• Rethinking the Strategy– J1772 is now standardized; an EVSE upgrade in progress– Will also add a larger charger onboard
Control Board• Contactor Control
– Primary Contactor, Secondary Contactor, and KSI relay– Lockouts:
• Inertia Switch – deactivates contactors on collision• “High Pedal” – accelerator must be “off” to enable contactors• Charger – cannot enable contactors when charging
– Recommended operation:• Primary ON when charging or enabled (turns on DC/DC)• Secondary ON when enabled• KSI ON when accelerator depressed
• Charger Control– Integrate the BMS with the Charger
• Instrumentation– Drive Dash Indicators, etc
Contactor Control – Off the shelf
Evworks – ZEVA EV management system www.evworks.com.au
Pacific EV – EVCM (EV Control Module)www.pacificev.com/pev_evcm_electric_vehicle_control_module.html
Control Board – In ProgressBattery / Ignition / Ground Inertia Switch
Primary Contactor
Secondary Contactor, KSI
PotboxMicroswitch
BMS Master
Vacuum Pump• Gast – original conversion
– Relatively noisy– Not integrated
• Tried the VBS– Works quickly; relatively quiet– High current draw (~20A)– Not integrated
• Settled on MES‐DEA– Well integrated– Quiet and low current draw
Heater• Had wired up a single element of a ceramic heater
– Did not work well• Considered alternatives
– Electric fluid heater– Propane, natural gas heaters, truck cabin heaters
• Finally– Wired up both elements of existing ceramic heater– Works well and quickly; fine for defrosting windows– Single “on off” switch so no automatic temperature control
• Conclusion– Ceramic is OK but need to consider temperature control– Should have a lockout so element is not “on” unless fan is on– Current draw (~8A) is acceptable
Lessons Learned• Cell Failure and Cell Diagnosis
– 2/44 Lithium cells replaced in pack so far• Contactor Control Failure
– Contactor would drop out when driving. Probably due to contact pitting in one of the relays
• DC/DC Converter and 12v Accessory Battery– Original conversion downsized the 12v battery. The TBS vacuum pump strained the 12v system and caused battery failure.
– Best way to measure is with a 12v analog meter• Coupler Failure
– Original clutchless conversion was misaligned and destroyed itself after 3500mi. Was redone.
Lead Acid Component Scorecard Component Now Major Dislikes
Batteries Trojan 30XHS – SLA Capacity, weight, weight distribution, safety
Battery Boxes Bolted Weight, durability
Drive System ADC 9” / Curtis 1231C Whistle when starting; No regenerationNo Integrated contactor control
Adapter Design Clutchless
Pack Charger Zivan NG3 ‐ Onboard 220V No 110V, not sealed, no BMS integration
DC/DC Converter Zivan NG1 Not sealed
Heater Ceramic Not functional
Vacuum Pump Gast/vacuum switch/reservior Noisy, not integrated
Contactors Albright Noisy, not sealed
Instrumentation PakTrakr, LEDs, ammeter High voltage in cabin, no data logging
Safety 2 contactors + fuse No Emergency Disconnect
Lithium Component ScorecardComponent Now Improvement areas
Batteries 44*160Ah ThunderSky A few more cells (8) would give more range and performance
Battery Boxes TIG welded aluminum Aluminum is fine, still thinking about overall mechanical design.
Drive System ADC 9” / Curtis 1231C Whistle when starting; No regenerationNo Integrated contactor control
Adapter Design Clutchless
Pack Charger Elcon 1Kw Has BMS integration; need a bigger model
DC/DC Converter Zivan NG1 Not sealed
Heater Ceramic Works now, but only one setting
Vacuum Pump MES‐DEA Better than Gast pump, but still too noisy
Contactors Albright Noisy, not sealed
Instrumentation eXpertPro, MiniBMS, LEDs Logging BMS in development
Safety 2 contactors, fuse, circuit breaker
In Progress• Currently
– Control Board Upgrade– J1772– Logging BMS– DC/DC Converter Upgrade
• Planning for Next Conversion– 1984 Pininfarina Spider
J1772 ‐ EVSE• Purchased EVLink / Schneider Electric from stock at Home Depot in Rohnert Park
• Installation requires 30‐50A 220VAC• 18’ cable was too short.
– Added a 12’ extension using a Bulgin Buccaneer 900 plug/socket (IP68, 32A, 600V)
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