Belt Alternator System (BAS) hybrid - general discussion thread

[California98Civic]

At the suggestion of Green Hornet on another thread yesterday, I am starting this thread as a place on EM to collect some specs on GM's BAS mild-hybrid. I am putting it in the "hybrids" subforum, but maybe it will belong in the ecomodding central subforum. Depends on how/if EM members participate.

The system's advantage to GM has been that it is relatively cheap to implement, since the electric motor can replace the alternator and starter and fits on the engine, belted to the crank pulley. For a moderately ambitious modder with fabrication skills, the advantage of such a system is the same. It is *relatively* easy to implement as a mod on a standard ICE.

I searched EM and found mentions of the BAS but no thread devoted to it. I'll come back to this OP to edit it for corrections.

There have apparently been two generations of this system, with the first being launched in 2007 and the second in 2012.

According to a Hendon Media Group article, a the system has five major components:

1) An electric motor / generator. AC current from the motor / generator is converted to DC current to charge the batteries, and vice versa.
2) A coolant-cooled power electronics that controls the motor / generator and provides 12 volts to the vehicle’s conventional battery.
3) A nickel metal hydride battery pack capable of 10 kW of power.
4) A separate engine-control module with Hybrid Supervisory Software to manage both the gas engine and hybrid system.
5) A different engine accessory drive with a dual tensioner assembly and aramid cord belt. This belt transfers torque to the gas engine from the electric motor for starting and acceleration, and torque from the engine to the motor to generate electricity.

And there is a more detailed and longer description from "Under Hood Service." Here is a key section describing the functions:

"The BAS alternator’s output is controlled by two modules: the main generator control module, and an auxiliary control module. In normal driving mode, the generator control module converts the alternator’s three-phase, 36-volt alternating current (AC) output to 36 volts direct current (DC) to keep the hybrid battery charged. In start/stop mode, the generator module also converts 36 volts DC from the hybrid battery back into 36 volts AC when the BAS unit requires power to restart the engine, or to provide some extra kick when accelerating."

And then these images and charts from around the internet:

[oil pan 4]

Another GM good idea that looked good on paper.
This was from back in the day when GM just thought people wanted a hybrid badge on their vehicle to be cool and didn't actually care about fuel mileage.
If I remember right the real world driving showed the same or less highway milage as the non hybrid and most of the city mileage improvement was attributed to the auto start/stop tech.

[California98Civic]

Originally Posted by oil pan 4

Another GM good idea that looked good on paper.
This was from back in the day when GM just thought people wanted a hybrid badge on their vehicle to be cool and didn't actually care about fuel mileage.
If I remember right the real world driving showed the same or less highway milage as the non hybrid and most of the city mileage improvement was attributed to the auto start/stop tech.

But part of that failure would be because nearly all driver would fail to understand how to use the system, and perhaps the system was not optimalized for their either. For example, if I had something like this in my Civic, I would use it heavily in electric only for initial launches from stops, for crawling around parkinglots, for stop/go traffic. And I would use the enhanced regen braking. I rig it for plug in. If I could to those things my FE would improve substantially.

[oil pan 4]

That motor generator GM used looks like it's maybe 1 to 2 horsepower. Pretty much useless for moving a 3000+ vehicle.

[California98Civic]

Originally Posted by oil pan 4

That motor generator GM used looks like it's maybe 1 to 2 horsepower. Pretty much useless for moving a 3000+ vehicle.

Some of the specs I saw claimed it could draw 10kw... so that would be more like 12hp, wouldn't it? EDIT: deleted a misread of the chart.

[oil pan 4]

10kw only very briefly like when restating the main engine.
10kw sustained would undoubtedly smoke it.
Then look at the motors natural environment, a hot 180°F engine compartment making it even more difficult to cool it's self and making usable horsepower even more difficult.

[GreenHornet]

This is a suitable motor that I will be using for a series hybrid project that would work well for a home built BAS system.These are Brushless and over 90% efficient. Use one of these models in conjunction with a sinewave controller and you would be in business. These are powerful, lightweight, inexpensive and can be customized to suit your needs. These are very robust and rugged motors that are also proven and no I am not affiliated with them in any way just know from many others that they are for real.

Brushless Motor Options:

#1. RV-160 Short | REVOLT
#2. RV-160 Pro | REVOLT

Sinewave controller options

#1. KLS7250D,24V-72V,400A,Sinusoidal Brushless Motor Controller - Kelly Controls, LLC
#2. KLS7275D,24V-72V,500A,Sinusoidal Brushless Motor Controller - Kelly Controls, LLC

Now battery options which will depend on how much electric you want if it is for just stop and go traffic and launches then you need for little in KWh less than 1kwhr to put in perspective. The first Honda Insight had less than 1kw in its pack of NiMH batteries. I would go with Lithium Iron Phosphate which are not the lightest most compact lithium batteries but are the safest and easiest to work with in my opinion. If you go with true 20ah 12V batteries then GBS are a good option for price and support. A 48V system would give you 960 watt hrs pretty close to the First Gen Honda Insight but these are Lithium so superior in my opinion. Or you could go 60V which I would recommend and then you are at 1.2 kilowatt hrs. With a larger car this would help a lot. Remember that the heavier the vehicle the larger system you need. More volts is more efficient. The Honda Insight first Gen used a 144V system. There are a ton of battery options available the first and most important thing to decide is priority like launching, stop and go etc then appropriate voltage to make it happen. Then you can go from there.

#1. Elite Power Solutions

[GreenHornet]

http:// http://gmauthority.com/blog/...k-engine-1.jpg

M 2.4 Liter I4 Ecotec Hybrid LUK Engine

The LUK is a hybrid engine system produced by General Motors for compact, midsize, and full-size vehicles. Displacing 2.4 liters in an I4 configuration, the LUK is part of the Ecotec engine family. It is essentially the LEA Ecotec but modified for GM’s Belt-Alternator Starter (BAS) mild-hybrid drivetrain. It is available on the Buick Regal eAssist and LaCrosse eAssist as well as on the Chevrolet Malibu and Impala.

Overview
Specifications
Vehicle Applications
Pictures

The Ecotec 2.4L LUK uses a state-of-the-art lithium-ion battery system and electric motor-generator to enable regenerative braking capability to improve fuel economy by an estimated 25 percent. The engine is based on the proven Ecotec 2.4L engine, but with features to support the eAssist system.

Engine highlights:

eAssist System: the eAssist system uses power stored in an advanced, 115V lithium-ion battery and channels it to a 15-kW motor generator to provide an electrical boost in various driving scenarios, optimizing engine and transmission operation and increasing fuel economy through:
Regenerative braking, which provides up to 15 kW of electricity to charge the battery
Providing up to 11 kW (15 hp) of electric power assistance during acceleration
Automatic engine shut-off when the vehicle is stopped
Aggressive fuel cut-off during deceleration down to zero vehicle speed, enabled by the torque smoothing provided by the motor-generator unit
Intelligent charge/discharge of the high-voltage battery.
Engine Block: the Ecotec 2.4L’s sand-cast cylinder provides excellent structural support, as well as enabling greater control of noise, vibration and harshness. The main bearing bulkheads, which support the crank bearing, as well as the cylinder bore walls, have been significantly strengthened to support increased engine loads.
Aluminum Pistons with Jet-Spray Cooling: the Ecotec 2.4L’s pistons use lightweight aluminum pistons, for less reciprocating mass inside the engine that enhances efficiency, decreases vibration and bolsters the feeling of performance as rpm increases. Each piston has its own directed jet that sprays oil toward its skirt, coating its underside and the cylinder wall with an additional layer of lubricant. The extra lubrication cools the pistons, reducing friction and operational noise, while also bolstering the engine’s durability.
Cylinder Head: the Ecotec 2.4L has a SPM 319 aluminum cylinder head that is cast with advanced semi-permanent mold technology. This provides excellent strength, reduced machining and optimal port flow. The cylinder head is designed specifically for direct injection into each combustion chamber and includes premium valve seat, valve guide and valve materials. The cylinder head also has integral cast oil passages that feed a set of internal oil control valves that activate cam phasers, enabling variable valve timing.
DOHC with Continuously Variable Valve Timing: overhead cams are the most direct, efficient means of operating the valves, while four valves per cylinder increase airflow in and out of the engine. This arrangement is integrated on the Ecotec 2.4L’s lightweight aluminum cylinder head. Both the intake and exhaust cams have hydraulically operated vane-type phasers that are managed by a solenoid and directed by the engine control module (ECM).
Direct Injection: direct injection moves the point where fuel feeds into an engine closer to the point where it ignites, enabling greater combustion efficiency. Direct injection also reduces emissions, particularly cold-start emissions, by about 25 percent. With direct injection, the higher compression ratio is possible because of a cooling effect as the injected fuel vaporizes in the combustion chamber. This reduces the charge temperature and lessens the likelihood of spark knock. The direct injection fuel injectors have been developed to withstand the greater heat and pressure inside the combustion chamber and also feature multiple outlets for best injection control.
Cam-Driven High-Pressure Fuel Pump: a high-pressure, cam-driven pump provides the fuel pressure required of the direct injection system in the Ecotec 2.4L. The engine-mounted fuel pump is augmented by a conventional electrically operated supply pump in the fuel tank.


Here is a link to read more = http://gmauthority.com/blog/gm/gm-engines/luk/

[GreenHornet]

Notice how GM has now gone to Lithium at 115V. Also notice that the E-motor is 11kw.

These are the main differences from the 1st gen BAS to the 2nd gen BAS.

The 2nd gen now uses Lithium vs the NiMH and you know have a more powerful E-motor up from 5kw to 15kw. Utilizing a larger more powerful 15kw motor gives it a practical E-boost that can be used in a more sustained manner. While 5kw was a good start it was no where close to what was truly needed for a 3,000lb vehicle. Another strong distinction is the increased voltage 115V is way more efficient than the 36V they used in the 1st gen system.

[California98Civic]

The system has its own cooling, right? The first generation had it's own water pump, separate from the engine, so that the system would be cooled even in start/stop mode. So you think any such system would require that? Seems like a DIY without some cooling system would get mighty hot, as Oilpan4 says above. A separate cooling system really increases the complexity and cost a bit, no?