{{Short description|Automotive hybrid engine technology}}

'''BAS''' ('''belted alternator starter''') is a category of automotive [[parallel hybrid]] technology that uses an [[electric motor]] to contribute power to the [[internal combustion engine]]'s [[crankshaft]] via a [[serpentine belt]]. By mounting this motor generator unit in the conventional location traditionally used for the standard automotive [[alternator (automotive)|alternator]], it permits a low-cost method of adding [[mild hybrid]] capabilities such as start-stop, power assist, and mild levels of [[regenerative braking]]. BAS systems differ from other mild hybrid systems as they are not run off the vehicle's crankshaft.

==Toyota== [[File:Toyota Crown Super Deluxe Mild Hybrid.jpg|thumb|[[Toyota Crown Sedan]] Super Deluxe Mild Hybrid]] In June 2001, [[Toyota]] introduced a BAS hybrid system under the Toyota Hybrid System-Mild (THS-M) brand name.<ref name="Toyota">{{cite press release |author=<!--Not stated--> |title=Toyota's "Mild Hybrid" System Boosts Fuel Efficiency 15% |url=https://global.toyota/en/detail/205157 |location=Japan |publisher=Toyota |date=2001-06-12 |access-date=2022-10-19}}</ref> It operates similarly to other mild hybrids with a [[start-stop system]], in that it shuts down the engine as the vehicle comes to a stop and instantly restarts it when the brake pedal is released.

THS-M is capable of modest power assist during launch acceleration and similarly modest levels of "blended" regenerative braking during deceleration. A 36-volt [[lead–acid battery]] (housed in the vehicle's trunk and operating in a [[42-volt electrical system]]) is used to operate a permanent magnet motor/generator unit mounted to the engine in a similar fashion to a conventional alternator. Then, through a high-tension drive belt, the motor/generator unit is capable of starting or assisting the engine. A conventional 12-volt battery and starter motor are retained and used whenever the engine is cold as during initial start-up.

Although unable to operate in pure all-electric [[Electric vehicle|EV]] mode, THS-M improves city and highway [[fuel efficiency]] over non-hybrid versions. According to Toyota, the system provides a 15% increase in fuel economy.{{r|Toyota}} The system is designed to be simple and easily adaptable across a wide range of vehicles, with no significant modifications required to the vehicle chassis to accommodate the system. This allows THS-M vehicles to be produced on the same assembly line as non-hybrid versions, producing substantial cost savings and allowing production to be adjusted more easily.

The first production model equipped with THS-M was the [[Toyota Crown#Eleventh generation (S170; 1999)|eleventh generation Toyota Crown]] Royal Saloon Mild Hybrid, introduced in August 2001, combining the system with a 3.0&nbsp;L [[Toyota JZ engine#2JZ-FSE|2JZ-FSE]] [[straight-six engine]].<ref name="Toyota timeline">{{cite web | url = https://www.toyota-global.com/company/history_of_toyota/75years/data/automotive_business/products_technology/technology_development/hv-fc/index.html | title = Technical Development-HV and FC | publisher = Toyota | year = 2012 | access-date = 2022-10-21}}</ref> It was followed in October 2002 by the [[Toyota Crown Sedan]] Super Deluxe Mild Hybrid, which combines the system with a 2.0&nbsp;L [[Toyota G engine#1G-FE|1G-FE]] engine.{{r|Toyota timeline}}

==General Motors== ===Generation I BAS=== [[General Motors]] introduced a BAS hybrid system in the 2007 [[Saturn Vue]] Green Line. The BAS is in the 2008&ndash;2009 [[Chevrolet Malibu]] Hybrid.<ref>[http://media.gm.com/servlet/GatewayServlet?target=http://image.emerald.gm.com/gmnews/viewpressreldetail.do?domain=34&docid=40267] {{webarchive|url=https://web.archive.org/web/20071218122835/http://media.gm.com/servlet/GatewayServlet?target=http%3A%2F%2Fimage.emerald.gm.com%2Fgmnews%2Fviewpressreldetail.do%3Fdomain%3D34&docid=40267|date=December 18, 2007}}</ref> It operates on the same principle as Toyota's THS-M using a 36-volt electrical system (at 42&ndash;45 volts).

According to the EPA, the 2009 Saturn Vue BAS hybrid garners an improvement of 32% city (19>25mpg) and 24% highway (26>32mpg) making the combined economy improvement 27% (22>28mpg) over the base 4-cylinder FWD version.<ref>{{cite web|url=http://www.fueleconomy.gov/feg/sbs.htm |title=Side-by-Side Comparison |publisher=Fueleconomy.gov |accessdate=2010-12-04| archiveurl= https://web.archive.org/web/20101206234502/http://www.fueleconomy.gov/feg/sbs.htm| archivedate= 6 December 2010 | url-status= live}}</ref> The system is reasonably simple and inexpensive, making BAS equipped vehicles some of the least expensive hybrids available.<ref>[http://media.gm.com/servlet/GatewayServlet?target=http://image.emerald.gm.com/gmnews/viewmonthlyreleasedetail.do?domain=35&docid=34380] {{webarchive|url=https://web.archive.org/web/20070622184406/http://media.gm.com/servlet/GatewayServlet?target=http%3A%2F%2Fimage.emerald.gm.com%2Fgmnews%2Fviewmonthlyreleasedetail.do%3Fdomain%3D35&docid=34380|date=June 22, 2007}}</ref><ref>{{cite web|url=http://www.hybridcars.com/compacts-sedans/saturn-aura-green-line-overview.html |title=Saturn Aura Green Line - Review |publisher=Hybrid Cars |date= |accessdate=2012-01-27}}</ref><ref>{{cite web|author= Sam Abuelsamid |url=http://green.autoblog.com/2007/03/19/saturn-aura-green-line-approved-for-tax-credit/ |title=Saturn Aura Green Line approved for tax credit |publisher=Green.autoblog.com |date= |accessdate=2012-01-27}}</ref>

Vehicles with the BAS system use a conventional [[GM 4T45 transmission|4T45-E]] [[automatic transmission]] which has been modified to include a more efficient final-drive ratio and includes an electrically driven pump to provide pressure in auto-stop mode. The [[air conditioning]] compressor continues to be operated through a belt-driven pulley, but for fuel economy improvement it can be disabled in auto-stop mode if the "ECO" A/C mode has been selected by the operator.

[[Cobasys]], which supplies the BAS system's battery pack, had to conduct a recall in 2008 due to apparent internal [[Battery leakage|leakage]] of the battery modules.<ref>{{cite web|last=Korzeniewski |first=Jeremy |url=http://www.autoblog.com/2008/06/03/doh-battery-leakage-hurts-gm-hybrid-production/ |title=Doh! Battery leakage hurts GM hybrid production — Autoblog |publisher=Autoblog.com |date=2008-06-03 |accessdate=2010-12-04}}</ref>

Citing supplier issues and slow sales, GM relegated the 2010 model year BAS hybrids to "fleet only" status.<ref>{{cite news| url=https://www.wsj.com/articles/SB124468842019805121 | work=The Wall Street Journal | title=GM Pulls Plug on Hybrid Model | date=June 11, 2009 | first1=John D. | last1=Stoll | first2=Sharon | last2=Terlep}}</ref>

===Generation II BAS (eAssist)=== At the [[LA Auto Show]], on November 15, 2010, General Motors announced that it would be releasing an all-new version of the BAS system available in the 2012 [[Buick LaCrosse]].<ref>{{cite web |url=http://www.autoweek.com/article/20101115/LOSANGELES/101119954 |title=L.A. auto show: Buick gives the LaCrosse an electric assist |last1=Migliore |first1=Greg |last2=Vaughn |first2=Mark |work=Autoweek |date=2011-10-15 |publisher=[[AutoWeek]] |accessdate=2011-08-25}}</ref> While still a Belted Alternator Starter system, the system is named eAssist and includes a larger more powerful Hitachi-supplied{{Citation needed|date=October 2013}} 115-volt lithium-ion battery and a {{convert|11.2|kW|abbr=on}} motor-generator that delivers {{convert|79|lbft|Nm|0|abbr=on}} of torque. The additional power provided by the more powerful battery and motor provides the ability to contribute more power, and more often able to electrically start and assist the 2.4L engine. The eAssist system also includes a specially modified [[GM 6T40 transmission|GM 6T40]] 6-speed automatic FWD transaxle.<ref>{{cite press release |url=http://media.gm.com/content/media/us/en/news/news_detail.brand_gm.html/content/Pages/news/us/en/2010/Nov/10los_angeles/1115_gm_lacrosse |title=2012 LaCrosse Comes Standard With New eAssist Fuel-Saving Technology, For 37 Mpg Highway Fuel Economy In A Full-Size Sedan |publisher=[[General Motors]] |date=2010-11-15 |accessdate=2010-12-04}}</ref><ref>{{cite web |url=http://green.autoblog.com/2010/11/16/2012-buick-lacrosse-eassist-achieves-up-to-37-m/ |title=2012 Buick LaCrosse eAssist achieves up to 37 mpg highway |date=2010-11-16 |publisher=[[Autoblog Green]] |accessdate=2011-08-25}}</ref>

===Generation III (BAS3)=== A third generation was introduced in the 2016 [[Chevrolet Silverado#Third generation Silverado / Fourth generation Sierra (2014–2018)|Chevrolet Silverado/GMC Sierra]] and can improve fuel efficiency by about 13%. This adds about {{convert|100|lb|kg|0|abbr=on}} to the total weight of the truck but provides an additional {{convert|13|hp|kW|abbr=on|0}} and {{convert|44|lbft|Nm|0|abbr=on}}. The eAssist system includes a modified [[GM 8L90 transmission|GM 8L90]] [[automatic transmission]]. It uses the same battery cells from the [[Chevrolet Malibu Hybrid]] and the software is a modified version of the [[Chevrolet Volt]]'s.<ref>{{cite web|last1=Smirnov|first1=Andre|title=2017 GMC Sierra 1500 eAssist Hybrid: Is There Future in Hybrid Pickup Trucks? [Video] - The Fast Lane Truck|url=http://www.tfltruck.com/2016/11/2017-gmc-sierra-1500-eassist-hybrid-is-there-future-in-hybrid-pickup-trucks-video/|website=www.tfltruck.com|date=19 November 2016 |accessdate=5 April 2017}}</ref><ref>{{cite web|title=Chevrolet Introduces 2016 Silverado with eAssist|url=http://media.gm.com/media/us/en/chevrolet/news.detail.html/content/Pages/news/us/en/2016/feb/0225-silverado-eAssist.html|website=media.gm.com|accessdate=5 April 2017}}</ref>

==Other names== *Belt-driven starter generator (BSG) *Belt-driven integrated starter generator or belt mounted integrated starter generator (BISG or B-ISG) *Belt-driven starter alternator or belted starter alternator (BSA) *Dynastart

==Vehicles== *2001&ndash;2003 [[Toyota Crown#Eleventh generation (S170; 1999)|Toyota Crown]] Royal Saloon Mild Hybrid *2002&ndash;2008 [[Toyota Crown Sedan]] Super Deluxe Mild Hybrid *2007&ndash;2009 [[Saturn Aura]] Green Line *2007&ndash;2009 [[Saturn Vue]] Green Line *2008&ndash;2010 [[Chevrolet Malibu]] Hybrid *2012&ndash;2014, 2018-2019 [[Buick LaCrosse]] with eAssist *2012&ndash;2014 [[Buick Regal]] with eAssist *2013-14 [[Chevrolet Malibu]] with eAssist *2014 [[Chevrolet Impala]] with eAssist *2016 [[Chevrolet Silverado#Third generation .282009-2013.E2.80.93present.29|Chevrolet Silverado/GMC Sierra]] with eAssist, only in California *2017 [[Audi A8#Fourth generation (D5; 2018–present)|Audi A8]]<ref>{{cite web|title=Versatile and efficient: mild-hybrid technology|url=https://www.audi-mediacenter.com/en/techday-on-combustion-engine-technology-8738/versatile-and-efficient-mild-hybrid-technology-8761|website=Audi MediaCenter|accessdate=13 March 2018}}</ref> *2017 [[Audi A7#Type 4G9 (2018–present))|Audi A7]]<ref>{{cite web|title=Second-generation Audi A7 Sportback features standard 48V MHEV system with gasoline or diesel engines|url=http://www.greencarcongress.com/2018/02/20180214-a7.html|website=Green Car Congress|accessdate=13 March 2018}}</ref> *2019-2020 [[Jeep Wrangler (JL)|Jeep Wrangler]] with eTorque *2019 [[Ram 1500 (DT)|Ram 1500]] with eTorque *2022 [[Jeep Wagoneer (WS)|Jeep Wagoneer]] with eTorque *2022 [[Jeep Grand Cherokee]] with eTorque *2021 [[Fiat 500 (2007)|FIAT 500]] Hybrid and [[Fiat Panda|FIAT Panda]] Hybrid,<ref>{{Cite web |title=features |url=https://www.fiat.it/modello/fiat-panda/features |access-date=2024-07-23 |website=www.fiat.it |language=it-IT}}</ref><ref>{{Cite web |last=Ruiz |first=Álvaro |date=2023-10-27 |title=Probamos el Fiat Panda Hybrid: el coche con etiqueta ECO más barato no puede ser más básico, pero cumple con lo que promete |url=https://www.motorpasion.com/fiat/fiat-panda-hybrid-2024-prueba-contacto |access-date=2024-07-23 |website=Motorpasión |language=es}}</ref> with BSG (Belt-integrated Starter Generator) *2023-2024 [[Audi Q5|Audi Q5 45 TFSI]] (12V MHEV)

==See also== * [[Start-stop system|Integrated starter generator]] * [[Parallel Hybrid Truck]] * [[Two-Mode Hybrid]]

==References== {{reflist}}

===Bibliography=== * {{cite web|url=http://www.motortrend.com/features/auto_news/2007/112_news071012_2008_saturn_vue_greenline|title=Saturn Vue Greenline|work=[[Motor Trend]]|accessdate=October 12, 2007| archiveurl= https://web.archive.org/web/20071014030431/http://www.motortrend.com/features/auto_news/2007/112_news071012_2008_saturn_vue_greenline| archivedate= 14 October 2007 | url-status= live}} * {{cite web|url=http://autoweek.com/apps/pbcs.dll/article?AID=/20060108/FREE/60108002/1024/LATESTNEWS|title=Going Green|work=[[AutoWeek]]|accessdate=January 9, 2005}} * {{cite web|url=http://www.gm.com/company/gmability/adv_tech/100_news/hybridvue2_10906.html |title=Saturn Vue Green Line Hybrid Delivers Great Fuel Economy Through New, Lower-Cost Hybrid System |work=[[General Motors Corporation|General Motors]] press release |accessdate=January 9, 2006 |archiveurl=https://web.archive.org/web/20060203030651/http://www.gm.com/company/gmability/adv_tech/100_news/hybridvue2_10906.html |archivedate=February 3, 2006 |url-status=dead }} * {{cite web|url=http://www.gm.com/company/gmability/adv_tech/100_news/hybridvue_10906.html |title=Saturn Vue Green Line Uses New, Less Complex Hybrid System |work=[[General Motors Corporation|General Motors]] press release |accessdate=January 9, 2006 |archiveurl=https://web.archive.org/web/20060315174408/http://www.gm.com/company/gmability/adv_tech/100_news/hybridvue_10906.html |archivedate=March 15, 2006 |url-status=dead }}

[[Category:Engine technology]] [[Category:Hybrid powertrain]] [[Category:Saturn Corporation]] [[Category:General Motors hybrid technologies]]