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Saturday, February 06, 2021

BAS : Belted Alternator/Starter Project : Mild Hybrid Nissan Skyline : Part 1

A couple things on my workbench at home one day. OEM R32 fuel tank top. Flex fuel sensor. BAS alternator/motor

My wife worked at GM, and she worked on/around the GM BAS system.  It's pretty basic. It's pretty mild. It was a stop gap type of thing. The part that interested me the most, was that the footprint of the BAS was about the same size as a conventional alternator.   That got me thinking. 

RB26 alternator on the left, BAS on the right
RB26 alternator in the background, BAS in the foreground

The RB26 is a small displacement, short stroke engine. It doesn't make a lot of bottom end. It just doesn't. You don't get a ton of torque down low, out of an engine with a 73.7 mm stroke, and a 121.5 mm C-C rod.   So, could you take a BAS, add it as an assist to an RB, and have it work from say idle to maybe 3000 rpm or so? Standing on it coming out of a corner, make up for some of that "Turbolag?"  Maybe you could even use it a little at cruise? It doesn't take much horsepower for a car to cruise at a steady speed on the freeway.   Maybe it might help improve fuel economy, maybe emissions. Emissions may not be on your mind, but with California regulations, and an engine that never was made for them, it's always on my mind. 

This is more just a brain exercise than anything else. The actual benefits will be pretty minor.   I was a gas turbine electrician in the US Navy in a past life.  Or rather right out of high school, I went into the Navy and learned about electrical control systems for gas turbine engines. I did what is called A and C School, then about four years on a ship. The types of control systems I worked on are ancient now, but also included things like UPS (uninterrupted power supply). 

These early BAS :

in the 2007 Saturn Vue Green Line. The BAS system is also used in the 2008–2009 Chevrolet Malibu Hybrid. 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.[1]

The BAS system is capable of providing modest levels of power assist during launch/acceleration and similarly modest levels of "blended" regenerative braking during deceleration. Although unable to operate in pure all-electric EV mode, the BAS system provides improvements to both city and highway fuel efficiency over similar non-hybrid versions. In more powerful eAssist versions, a BAS system can add power to prevent excessive gear changes under variable load. 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 4cyl FWD version.[2] The system is reasonably simple and inexpensive, making BAS equipped vehicles some of the least expensive hybrids available.[3][4][5]

36 volt electrical system (operating at 42–45 Volts) 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 BAS system is capable of starting or assisting the 2.4L Ecotec engine. A conventional 12V starter motor is retained and used whenever the engine is cold as during initial start-up. 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.

Vehicles with the BAS system use a conventional 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.

One perceived benefit of the BAS technology is that it fits in the same space as a conventional engine. No significant modifications were required to the vehicle chassis to accommodate the BAS system, with the 36V battery pack housed in the trunk or spare tire well. This allows the vehicles to be produced on the same assembly line as the non-hybrid versions, producing substantial cost savings and allowing the company to adjust production more easily.


I don't see using it as start stop, as you need to know the position of the engine to properly do that. An oem or near OEM RB setup, doesn't really know where the engine is. It would need a dedicated crank pickup, and maybe another cam sensor to really do that.  So just a boost in a range is the first ideas for it. Sort of like a nitrous shot. On and off at setpoints.  I have the controller, and I bought a Honda Clarity battery pack. 48 v. 

The green line being the early BAS system. 36v run at 42-45 volts

Someone asked me what car I am going to run this on. The funny part was I didn't have an answer. I wasn't really thinking about the car, just the system, and trying to make it work.  I know the early BAS on the Saturns had issues with belts and tensioners related to start and stop. 

The parts of my mild hybrid Nissan Skyline system. 

2007-2009 Saturn Vue Hybrid, 2008-2010 Malibu Hybrid Alternator Assembly
SATURN VUE Hybrid Generator Inverter Converter Control Computer Assembly
Honda Clarity 48v 1.2kWh Lithium Ion Battery module
The Honda Clarity battery pack was priced right. 48 volts. 1.2kW 14 3/4 inches long
6 inches wide 4 1/2 inches tall  24lbs

So pretty compact, and not that heavy.  Weight is always a concern, as we dont want to add any more weight than we have to. You will take away all the benefits by adding too much weight. 




I have the service manual for the Saturn Vue Hybrid. I don't have the Honda Clarity pack information, but its not that complex. Mostly just monitoring the SOC of the battery. I am probably just going to buy a complete used Saturn Vue Hybrid SUV to learn a little more about the system. They aren't that expensive, and it will be an easy way to look at a functioning system. 

If I did want to do a start/stop with an aftermarket ECU, crank and cam pickup, I would probably try and convert the front of the engine to a serpentine belt. My first thoughts were its possible, like anything. 


The later version which is called BAS plus, or eAssist is larger, probably wouldn't fit in an alternator footprint as well is rated : 115 Volt Lithium Ion battery and a 11.2 kW (15.0 hp) motor-generator that delivers 79 lb⋅ft (107 N⋅m) of torque

For now this is not a high priority project. Just something to keep my brain entertained. If you aren't thinking about new and unconventional things, where are you really? 

Ecomodder Forum - GM BAS


GM BAS connector on the controller. Need to start looking at pin outs

GM BAS connector on the controller. Need to start looking at pin outs



This was kind of cool. This guy converted an alternator to a motor for his electric bicycle. This video shows some of his struggles. 






A few years ago I converted a car alternator into a go kart motor. In this video I build an alternator powered bicycle. I originally tried controlling the motor with a sensorless controller but did not achieve the performance that I was hoping for. After installing hall effect sensors into the motor the results have far exceeded my expectations. The alternator is from a 1998 Ford F-150. Converting a Car Alternator into a Go Kart Motor: https://www.youtube.com/watch?v=IKqy3... Hall Effect Sensor Placement Article: http://mitrocketscience.blogspot.com/... Follow Me: Instagram: https://www.instagram.com/austiwawa/


Honda Clarity Battery

I know what this does. + battery voltage

What do these pins do? Two wire is almost always something basic like a switch or sensor. 

What do all these pins do?

GM BAS connector on the controller. Need to start looking at pin outs

GM BAS connector on the controller. Need to start looking at pin outs

GM BAS connector on the controller. Need to start looking at pin outs



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