Details of the Audi Q5 Hybrid Quattro Li-ion battery pack
01 February 2011
by Jack Rosebro
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| Components of the Q5 hybrid system. Click to enlarge. |
In a presentation at the 2011 Advanced Automotive Battery Conference (AABC) in Pasadena, California last week, Daniel Andree, a battery development engineer at Audi AG, outlined the implementation of a Sanyo lithium-ion battery pack in the upcoming 2012 Audi Q5 compact crossover hybrid. (Earlier post.)
The Q5 has an all-electric range of about 3 km (a little less than two miles) with a maximum all-electric speed of 100km/h (62 mph). The vehicle’s electric drive is mated to a 2.0L, turbocharged, direct injected four-cylinder gasoline engine. Combined weight of all hybrid components is less than 130 kg (286 pounds).
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| SoC window for the Q5 Hybrid battery pack. Click to enlarge. |
Battery pack performance. The 266V, 1.3 kWh battery pack weighs about 35 kg, yielding a power density ratio of 1143 W/kg and an energy density ratio of 37 Wh/kg. The cells themselves account for slightly more than half of the pack’s total weight (ratio of cell weight/system weight of 0.52).
The battery pack, which supplies 40 kW of a 180 kW total powertrain output, utilizes a broad maximum state-of-charge (SOC) window ranging between 20% to 80% pack charge, with full pack performance available between 30% and 70% SOC. (This is a much wider SoC window than some other automakers, such as GM, are currently utilizing for hybrid applications. GM, for example, is looking at a pack SOC window for a full hybrid of less than 20 percentage points. Earlier post.) Engine cranking is possible at temperatures as low as -30ºC (-22ºF) as long as battery pack SOC is 30% or greater.
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| Overview of the pack cooling design. Click to enlarge. |
Cooling the battery pack. The Q5’s battery pack is air-cooled, with cooling air volume and temperature controlled as needed. The pack is split into two symmetrical parts, each with its own inlet and outlet interfaces.
Particular attention was given to preventing turbulence within the air passages, which could lead to uneven pressures and cooling. Audi also found that a battery pack air conditioning system could significantly shorten the time to reach a specific cooling target. For example, an active battery pack could be cooled from 50 ºC (122 ºF) down to 40 ºC (104 ºF) by an air conditioning system in approximately sixteen seconds, as compared to approximately six seconds via forced-air cooling alone.
The battery management System (BMS) can switch between passive and active modes. If the battery pack temperature rises above 34.5 ºC (94.1 ºF), fan cooling is activated. If pack temperature rises above 37 ºC (98.6 ºF), the vehicle’s air conditioning system is activated, cooling interior air via the front evaporator. At 42 ºC (107.6 ºF), a dedicated rear evaporator provides additional cooling capacity.
| “The electrification of a conventional vehicle concept has a very big impact on nearly all parts of the vehicle. For example, to merge the conventional Q5 with the q5 hybrid, you will find differences in nearly all parts of the vehicle.” |
| —Daniel Andree |
Performance monitoring. The Q5’s battery management system stores historical stress data-cell resistance and capacity, pack temperature and current distribution, and violations of parameter limits—which can be displayed as histograms for evaluation. Audi’s testing indicates that in a worst-case scenario, battery pack capacity will be reduced to about 60%, with cell resistance increasing by 30%, by the end of the battery pack’s usable life. Audi expects to see no impact on battery performance during the battery pack’s first ten years of service, and intends to offer at least seven years of battery warranty, depending on vehicle miles driven.
Safety protection. The Q5’s battery pack protection is divided into three levels:
Protection Level 1: The vehicle’s battery management system detects cell imbalance (reduced cell capacity, increased cell resistance) and uses an algorithm to modify battery management strategy without affecting perceived vehicle performance.
Protection Level 2: The vehicle’s control system can isolate the battery pack from the rest of the hybrid system, shutting off current flow, if the pack exceeds given voltage, current, and/or temperature thresholds, or if a collision is detected. Battery function may be restored following a crash, depending on the intensity of the crash.
Protection Level 3: Mechanical and functional countermeasures are in place to prevent a chain reaction of thermal runaway in the event of a severe defect within one cell. Pack tests have been conducted in which one cell was purposely subjected to thermal runaway, to see if the effect would propagate across the pack. In all tests, the thermal event was confined to the original cell.
Q5 battery pack testing was conducted in accordance with UN lithium battery testing requirements, as well as those developed by Sandia Laboratories Test 2005-3123, which is used by Sandia itself in support of USABC FreedomCar testing contracts. Audi also added a "foreign particle" test to the abuse testing protocol for the pack. A nickel particle was built into to a cell to create a fault in which a cell’s separator would rupture under stress. No fire or explosion occurred during testing, according to Andree.
The 2012 Audi Q5 Hybrid Quattro is scheduled to be released in Europe this spring, and in North America later this year.
The more EV drive advances, the more understanding and economic scale.
Posted by: kelly | 01 February 2011 at 07:57 AM
3 kilometers in all electric mode...how many watts is that? 600 watts? I wonder how different the volume, weight and cost would have been to do ~600 watts of supercaps? What all-electric mode does is lets them run the ICE at optimal RPM and charge the battery, then turn off for a minute, then recharge again. This "saw tooth" usage cycle has the potential to reduce fuel consumption a couple ways...optimal rpm efficiency and off half the time...could lead to near doubling of fuel efficiency. Without a supercap to give you the luxury of unlimited recharge cycles and long life, that saw tooth charge-depletion schema would have drawbacks for longevity of the system.
Posted by: HealthyBreeze | 01 February 2011 at 09:24 AM
It's not watts, it's watt-hours. You get horsepower from watts and distance from watt-hours. The Q5 is a hybrid, which means the battery is used only for short-term acceleration or power boost, or load leveling, etc. I didn't read anything about "sawtooth" operation, but I'd like to know more about how the system works.
Anyway a typical BEV would get 4-5 miles per kilowatt-hour. This battery is only 1.3 kwhs and gets only 3 kilometers, less than two miles. It also has only 70 wh/kg, which is very low. I'm used to reading about 100-200 kwh batteries. However, if the battery was Altairnano's Titanium battery, they get only 50 wh/kg, but charge in about 5 minutes. But, this battery is only 1.1 kw/kg, so it would take about one hour for a full charge on a 110VAC, 15 Ampere circuit. It's not a plug-in anyway, so charging isn't an issue.
Posted by: Zhukova | 01 February 2011 at 10:35 AM
It would be good to build a mini-PHEV with double the battery capacity (2.6 KwH). Any more and it would get too expensive and heavy.
It would also be nice to see this added to an A3 or A4.
Posted by: mahonj | 01 February 2011 at 10:35 AM
Don't you just love the range.
Posted by: Mannstein | 01 February 2011 at 12:11 PM
3Km all electric range, 1.3KWH pack...., this is just ridiculous.
After having let the world dream of their advanced eTron concepts, how can AUDI lets us all down and come out with just another meaningless 1st Gen Hybrid / Power-Hybrid ?
Nobody wants that any more.
We want Plug In Hybrids with extended range. Question is to get to >300KM all electric range, with fast recharge capabilities, so we can recharge only twice per week for std commutings, making our life easier and batteries last much longer too.
STOP THESE NON-SENSE PLEASE.
Posted by: CARL75014 | 01 February 2011 at 12:49 PM
@Carl,
I understand your sense of being let down. However, until batteries come down a lot in price, weight and volume, hybrids are step in the right direction. If you could have 50% of the vehicle fleet 1st-generation hybrids, or 5% of the vehicle fleet all-electric...which would be better for the environment and the economy?
Posted by: HealthyBreeze | 01 February 2011 at 01:58 PM
"We want Plug In Hybrids with extended range. Question is to get to >300KM all electric range, with fast recharge capabilities, so we can recharge only twice per week for std commutings, making our life easier and batteries last much longer too.
STOP THESE NON-SENSE PLEASE."
And you forgot to mention that you dont want to pay $15k for that battery pack either.. and that is what it costs.
Posted by: Herm | 01 February 2011 at 02:02 PM
Carl, why not charge every day or twice a day? That lets you get by with a much lighter, smaller, cheaper battery. After all, plugging something in and walking off is a lot easier and less time-consuming than dealing with liquid fuel.
Posted by: Engineer-Poet | 01 February 2011 at 06:54 PM
Every journey stats with a single step.
While many of us are waiting for a drop in replacement to gasoline like mileage, lets not forget that many vehicles are used for short commutes.
This will be of benefit in the majority of urban stop start traffic jams.
Posted by: Arnold | 03 February 2011 at 08:59 PM
@ Herm
No 15K$ of battery pack can be OK. We're looking at a Mid-Range Audi SUV here, means >50K$ pricing range, not a cheap model.
Audi can put a lot of batteries into that amount, as long they implement their own eTron concepts instead of following others' 1st Gen hybrids forever approaches :
- Pull the huge central engine and gearbox and transmissions..., not needed any more.
- Move "tracting engine" to all electric, ideally one engine/weel. They are light, cheap, efficient, resiliant.
- Just put a cheaper/reduced ICE engine optimized for Power Generation, not for tracting, to cover for the extended range (Could be a new type of engines : Gaz Turbine, rotative... Things more efficiant at constant speeds).
- With all the $ and weight and space saved you can fit LARGE battery packs, especially in an SUV formfactor !
This is what the Volt did magnificiantly, inspiring the world, with some differences. Why could that be done in Lower price bands and not on expensive cars ? I hate that "BOBO" vision that new Plug In Hybrids would need to come in lower price bands 1st.
This is an historical non-sense. New techs always arrived in High End segments then migrated to mid range and low end as economies of scale take their costs down.
- Audi has shown the way with eTron their lack of execution is questionning their image, and reason of being, for me.
I own a beloved BMW 535DA that I need to replace within a year or 2. BMW will comout with nothing serious in that timeframe, too bad for them. I always looked at Audi as a valid alternative to BMW although never bought any so far. If they bring no mid-range eTron SUV in that timeframe, I'm ready to move from German Brands to US or even Japan Brands.
Posted by: CARL75014 | 05 February 2011 at 01:47 AM
Carl, you're starting to sound like me. I suggested some time ago that the problem with the Chevy Volt is that it had a Chevy nameplate but Cadillac potential (and now also a Cadillac price tag). The luxury segment can take very good advantage of all the other properties of a PHEV: quiet, smoothness, independence of accessories from the engine, and very infrequent trips to the filling station. But the execs thought "fuel saving = econo car", and the rest is history.
Posted by: Engineer-Poet | 08 February 2011 at 03:55 AM