Scotty AI V3 and the Bi-directional Motor Generator

This interactive publication describes how Bi-Directional Motor Generators work and their comparison to Alternators

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Scotty AI V3 and the Bi-directional Motor Generator Confidential and Proprietary. This information is copyright Safiery Pty Ltd 2025 Scotty Ai is protected by International Patent

What is a Bi-directional Motor Generator and how does it differ from an Alternator? o A BGM is at it’s core a Permanent Magnet Generator which is a synchronous machine with rotor windings replaced by permanent magnets. They need no separate excitation so rotor excitation losses – about 30% of total conventional generator losses – are eliminated. This results in high power density and small size with the highest efficiency at all speeds, offering the maximum annual production of energy with the lowest lifetime cost. A PMG is an AC device like Alternators. o PMG’s require an inverter that converts AC to DC to control them. At the rear of the Safiery BMG is an integrated inverter. The inverter is a power electronics device that manages the supply of current to the stator windings of the motor, controlling the speed and torque of the motor: 1. Frequency: Determines the motor's rotational speed. 2. Controls the electromagnetic field in the stator for torque generation. 3. Dynamic Response: Provides fast torque control for typical generator applications. o Advantages of Inverters:

1. High Precision Control. 2. High Energy Efficiency. 3. Flexibility to operate efficiently over a wide range of speeds and load conditions.

o What’s special about the Safiery BMG is HES Technology (Hybrid Excitation Synchronous). This combines both permanent magnet (PM) excitation and electromagnet excitation at the Stator (not rotor). This hybrid excitation mechanism overcomes the limitations of conventional synchronous generators requiring HIGH magnetic flux at low RPM. The Safiery BMG outputs more than 2000W at idle compared to a few hundred watts with a traditional 48V alternator and remote regulator.

Traditional Alternator with Diode Rectifier or Remote Regulator (Wakespeed)

Comparison of Technologies

Permanent Magnet Generator (PMG)

SAFIERY BMG 48V Only

Power Level

Very high

Low to Moderate

High

Efficiency

High

Moderate Excellent Moderate Moderate

Very High Excellent

Flux Control

Limited

Cost

High High

Moderate to High

Torque Density

Very High Very High

Application Flexibility

Moderate

High

Safiery Pty Ltd ABN: 87 624 588 807 45/8 Distribution Court, Arundel QLD 4214 (07) 210 22 55 3 safiery.com Confidential and Proprietary. Copyright Safiery Pty Ltd 2025 Scotty Ai is protected by International Patent o Scotty AI V3 has 3 CAN ports: 1) Drives the Integrated DC-DC, 2) Reads 48V Lithium battery CAN BMS and 3) Drives the BMG. The BMG and 48V Lithium battery can also be sitting on the on the Victron bus with no negative impact to Victron control. If no CAN BMS on Lithium Battery, Scotty AI V3 can still drive the BMG. Read detailed requirements below. Watch for Test Rig Videos on our Youtube channel beginning in late January 2025. o Scotty AI V3 combines with the Bi-directional Motor Generator (BMG) over CAN bus to give a wide variety of high-power control in either 12V, 24V and 48V.

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Safiery Pty Ltd ABN: 87 624 588 807 45/8 Distribution Court, Arundel QLD 4214 (07) 210 22 55 3 safiery.com Confidential and Proprietary. Copyright Safiery Pty Ltd 2025 Scotty Ai is protected by International Patent o In the unlikely event the battery relay opens quickly before the BMG is completely shut down, the stored energy is called a “load dump”. The digital response speed of SCOTTY AI V3 is in milli- seconds resulting is a tiny amount of contained energy. This very small, contained energy reverts o Safiery use Manual Service Disconnects (from EV Industry) installed on Safiery 48V battery circuit and connect the High Voltage Interlock feature of these MSD’s to SCOTTY AI V3 to prevent the BMG from running should the battery be isolated. This is a key requirement as if solar is connected, the 48V reading may remain high. Without an interlock, arcing and fire risk may occur. Second Alternator Position or Only One Unit replacing Factory Alternator: o SCOTTY AI V3 can be mounted outside of the engine bay with a waterproof NMEA style connection to the BMG data plug. The actual 48V power goes directly from the BMG to the auxiliary 48V battery system. In this setup, the BMG would be in a second alternator position in the vehicle or on the marine engine. On the marine engine, if the engine power is low, the second alternator position is opposite the primary alternator to balance the load on the crankshaft. SCOTTY AI V3 can be connected in several ways as further described in this document. o SCOTTY AI V3 can be mounted outside or inside the engine bay with the BMG replacing the factory alternator and the 12V or 24V DC-DC feed from SCOTTY AI V3 charging the lead acid starter battery. In this scenario, there is just one unit, the BMG, attached to the engine. The additional charging from a second factory 12V or 24V alternator is then not possible. Mild Hybrid and Free Power Control described in this document is still possible. 2. Initialization: o SCOTTY AI V3 determines if the mode of operation is power generation or charging or idle. o SCOTTY AI V3 initializes battery parameters State Of Charge, State Of Health and checks for alarms from the battery BMS. Charging Control at 48V from the BMG: o SCOTTY AI V3 drives the BMG with real-time torque and speed whilst monitoring the output Voltage and Current and making control adjustments. o SCOTTY AI V3 determines the optimum voltage and current charging parameters based on battery voltage, state of charge, charge current limit and temperature. Should the battery temperature be below the safe charging limit, SCOTTY AI V3 will not charge. o SCOTTY AI V3 changes the real-time torque and speed when the battery approaches maximum State of Charge; and/or the BMS Charge Current Limit indicating the battery is approaching maximum charge state. o The BMG is a vector controlled permanent magnet generator with additional windings on the stator for high power output at idle. There are no windings on the rotor, it is completely inlaid with permanent rare earth magnets. There are no diodes as with conventional alternators. As a result, efficiency of the generator is 90% and the inverter/controller connected is 94% giving a combined 85% round trip efficiency. Compare that to a traditional alternator at 60-70% when hot. External regulators like Wakespeed 500, Balmar or Zeus control the field current on traditional alternators. They don’t achieve this level of efficiency and are a field control add-on. There is no comparison. Safety is number one feature Load Dumps are controlled: o SCOTTY AI V3 stops the BMG should the battery voltage start to reduce suddenly indicating Battery relay is opening to stop over charging.

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through SCOTTY AI V3 bi-directional feature to the 12V starter battery or if not connected dispersed with a max controlled voltage to 12V loads. This is a complete contrast to traditional 48V alternators and external regulators which control of field current with more than a 1 second delay. In that amount of time, the contained energy of the “load dump” is considerable. Generally, the battery/controller cannot respond fast enough should the battery relay open in these traditional alternators with external regulators unless pre-warning is issued 2 seconds ahead of time. This is hard to guarantee. o SCOTTY AI V3 stops the BMG when an alarm is sent from the battery BMS and/or the BMS Charge Current Limit is reached and/or the BMS sends a reduced Charge Voltage limit indicating the battery is approaching maximum charge state. There is also a feature-in wire to stop charge. o SCOTTY AI V3 stops the BMG when temperature approaches setpoint set in APP protect the system from overheating. It starts to derate at maximum BMG temperature less 10C. Power Control in Mild Hybrid Mode: o SCOTTY AI V3 needs to read throttle position from vehicle ECU and based on that, changes mode from Charging to Idle to Power control. This is an optional feature and needs availability from the ECU on vehicle CAN. o SCOTTY AI V3 operates the BMS as a Mild Hybrid. It allows power control when throttle position is neutral until connected 48V battery reaches target minimum voltage set in the App. This will add torque to the engine and reduce fuel consumption when the vehicle is idling or starting out. It assists the automated “Start/Stop” function of vehicles. Variable Power Control to Harness Free High Power: o An alternative to the Mild Hybrid operation is to change the charging level to “Hard” when the throttle position is neutral, and when the throttle position is positive change to “Soft”. The result is charging the auxiliary 48V battery at the maximum level when the vehicle is coasting or braking, effectively harnessing “free energy”. Then when accelerating, the BMG and DC-DC load on the engine is soft. The added advantage of this approach is the BMG is relaxed for a maximum output and not 100% duty cycling at max. This results in a higher aggregate output. Charging Control at 48V from 12V Starter Battery and factory alternator: o SCOTTY AI V3 drives charging either to the same connected 48V battery or an entirely independent 48V battery system using the in-built DC DC feature. If connected to the same 48V battery as the BMG then control is synchronised between the two units with exactly the same battery control and safety provisions. In this case the power output of the combined unit is maximised to approx. 10kW if the 12V factory alternator is 250A and above. The full functionality is described in the manual and supported by a configuration and real time monitoring app. This is a standard included feature. The high output 12V alternator is either factory provided or an optional after-market unit. o SCOTTY AI V3 can charge as described above from either a 12V starting system or a 24V starter and battery system. o SCOTTY AI V3 determines the optimum voltage and current charging parameters based on battery voltage, state of charge, charge current limit and temperature.

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o SCOTTY AI V3 changes charging parameters when the battery approaches maximum State of Charge; and/or the BMS Charge Current Limit indicating the battery is approaching maximum charge state. o SCOTTY AI V3 changes charging parameters should the user select “soft, Medium, or Hard” from the touch display Power Control to either 12V or 24V starter battery and /or loads: o SCOTTY AI V3 delivers the lower voltage at a regulated maximum “camping voltage” set by the user in the App. o SCOTTY AI V3 can charge a low voltage 12V or 24V battery with a selected charge profile as an option selected from the App. o SCOTTY AI V3 controls the maximum power set by the App at a controlled max voltage and discharges to a minimum voltage on the connected 48V side battery to prevent this battery from discharging completely. If the starter battery is connected, a 12V or 24V Smart Battery Protect unit (optional) prevents it from discharging completely. Fault Handling: o SCOTTY AI V3 displays fault codes on the connected App. o The status LED changes from pulsing green to red if a fault occurs. o Should the CAN or battery communication system fail, the BMG can operate in a limp home mode with minimal output yet enough to drive a 48-12V or 48-24V DC-DC to power an engine if the BMG replaces the single factory alternator.

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Engine Compatibility o Currently available is Sprinter, Yanmar and USA truck engines pad mount o Scheduled to release Q1/Q2 2025 is LC79 and LC200 as factory replacement single alternator with BMG; RAM 2500, F250 and GMC second alternator mounts. J180 Mounts for other marine engines. o Scheduled release Q2Q3 2025 Isuzu double mount 24V factory + 48v BMG. Vehicle Pictures below: Sprinter, Ford, Cummins

Marine Pictures below: Volvo, Yanmar engine second alternator position

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Comparison of BMG to Old School Alternator

Hybrid 48V 300A Peak Bi-directional Motor Generator with Scotty AI (BMG) Hybrid Excitation Synchronous Generator (permanent magnets + hairpin windings)

Traditional 48V 130A Alternator with Wakespeed 500 remote field control.

Winner

“Alternator” Type

Field-excited rotor only

BMG

16 permanent magnets + excitation windings

Rotor Design

Field windings only

BMG

Power Density

1.65 kW/kg (advanced hairpin)

Lower due to round-wire winding

BMG

Brushless Motor: IP25. Waterproof Inverter: IP6K9K

Generally Brushed IP23 or lower

IP Level

BMG

Dual Stator Design

Dual three-phase, 30° shifted

Single three-phase

BMG

Ripple Current Reduction

Significant (30° phase shift)

Higher ripple

BMG

Noise Vibration Harshness Performance

Optimized (low ripple and torque smoothness) Higher (permanent magnets + hairpin winding)

Higher NVH

BMG

Efficiency

Lower (field-excited losses)

BMG

Fault Tolerance

Dual stator allows operation in partial failure

Single stator, no redundancy

BMG

Peak Generator Power

12 kW

6.2 kW

BMG

Peak Efficiency

≥ 85%

60–70%

BMG

Power at Idle (engine ~600RPM)

3.0kW

300-500W Typically

BMG

Continuous Power Hot

≥ 5.5~7.0kW

5~7.0 kW

BMG

Maximum Speed

18,000 RPM

~8,000–10,000 RPM

BMG

Operating Temperature

-40°C to 105°C

-20°C to 80°C

BMG

Lifetime Expected

10 years, 300,000 km, 8,000 hrs

5–7 years, 150,000–200,000 km

BMG

12V, 48V Negative Isolation to Earth

Yes

BMG

Integration with Factory 12V or 24V Alternator

Full Integration for added power as solar backup at idle

None

BMG

Inverter/motor diagnostics, 100% load dump protection

Load Dump Protection

Limited and depends on Battery

BMG

ISO 26262 ASIL B Automotive Safety

Compliant

Not compliant

BMG

Insulation Grade

Grade H (180°C)

Grade F (155°C)

BMG

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Safiery Model

SHSA4801 – Max 300A Peak at 48V

SHSA4802 – Max 240A Peak at 48V

Operation Voltage

24V or 48V Power up to 60V

-40 ℃ ～ 105 ℃

Operating Temperature

Maximum DC Output

300A@48V

240A@48V

Application

Trucks

4WD, SUV, Sprinter and Vans, Marine Engines 8.2 KW @ 25 ℃ (ambient temp),6000RPM 6.6 KW @ 55 ℃ (ambient temp),6000RPM 500 RPM engine speed 70A@1500RPM alternator speed at 48V

8.9 KW @ 25 ℃ (ambient temp),6000RPM 7.3 KW @ 55 ℃ (ambient temp),6000RPM 500 RPM engine speed 80A@1500RPM alternator speed at 48V

Continuous Power

Turn-on Speed

Maximum Speed

18000 RPM Intermittent

Control Mandatory Requirement to Operate

Scotty Ai V3 3000W or 1500W Model; RVC is available for Sprinter

Most BMS with CAN controlled Lithium Batteries. Lithium Batteries without CAN BMS can be managed but a stop charge function on these batteries must be available. Scotty Ai V3 manages many non compliant Lithium battery banks.

24V or 48V Battery Compatibility

Temperature Protection

Yes

Load dump Protection

Yes

Weight

9 KG

7.7 KG

Dimension

164 L x 150 D mm

156 L x 150 D mm

Overal Efficiency

85%

Cooling

Integrated Dual Fans

Rotation

Clockwise/ Counter Clockwise

Pulley

PK belt specification

Case Construction

Cast and Billet Machined Aluminium Alloy

Mild Hybrid Mode

Yes Available as an option see body of document for requirements

Isolation Level

H Insulation Class H is rated to withstand a maximum operating temperature of 180°C

IP Level

Motor: IP25 Inverter: IP6K9K

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Additional Safety Levels

Functional Safety: ISO 26262 ASIL B

o What It Means: 1. Compliance with ISO 26262 ASIL B ensures the system meets safety requirements for automotive applications where moderate safety-critical functions are needed. o Comparison: 1. Traditional alternators are not designed to meet functional safety standards like ASIL B.

Inverter and Motor Diagnosis and Protection

o What It Means: 1. Includes built-in diagnostic tools for the inverter and motor to monitor performance and detect faults (e.g., overvoltage, overcurrent, or overheating). 2. Provides protection against load dump (a sudden voltage spike when the battery is disconnected), ensuring system stability and longevity. o Comparison: 1. Traditional alternators with Wakespeed 500 lack integrated motor diagnosis and load dump protection; they depend on external BMS control for this.

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Impact on Fuel Consumption with a high output BMG on Marine Engines Key Insights Using Performance Curves of Yanmar 420CX as Example o The BMG load at maximum output has a minimal adverse impact on overall system efficiency at cruising speeds.

o In some cases, adding the BMG load improves the fuel efficiency of the engine by moving it closer to its optimal operating range. o Adding a 9 kW BMG load to the Yanmar 420 CX engine at cruising speed increases fuel consumption by approximately 2.74 liters/hour or about 5.4%.

o This is a relatively small impact, demonstrating the efficiency of using the BMG within the engine's cruising efficiency range. o There is no impact on boat speed because of the white space to propellor load. The Torque Curve o Torque is the twisting force on your prop shaft. You could have all the power in the world, but if the shaft didn’t spin you’d have no torque and no go. Torque is actually defined with the formula: Torque, KGM = (975.175 x kW)÷ RPM o The torque curve shows the torque generated by this engine at various RPMs. The interesting o thing is that maximum torque on normal internal- combustion engines doesn’t occur at maximum engine rated power and RPM. In fact, the torque curve of the 420 CX Yanmar is pretty typical. The maximum torque occurs at about 77 percent of maximum RPM, or 2,100 RPM. Indeed, on most engines maximum torque falls somewhere be- tween about 55 percent and 80 percent of max RPM. (Light gas engines tend to have peak torque at lower engine RPMs and heavy diesels at higher RPMs.) The units for the torque curve are in kgm (kilogram meters) and Nm (Newton meters). This is the metric equivalent of pound feet. We’re not particularly concerned with the absolute numbers; however, we’re simply interested in where torque is highest. o It simple terms, the 420 CX Yanmar is delivering the most oomph per gallon of fuel consumed from 2,100 RPM. This wouldn’t be a bad low-cruising speed, but you don’t unnecessarily want to limit operating speed this much. Let’s see how fuel consumption fits into the picture. Specific Fuel Consumption o The specific fuel consumption curve reads—as is often the case—in rather inconvenient units. In this instance, in grams per kilowatt per hour (g/kW). For the moment, though, what we’re really interested in is the shape of the curve and where fuel consumption is lowest for the output power and torque. In other words—just the opposite of the power and torque curves— the best spot on the specific fuel consumption curve is where it’s lowest. For the 420 CX Yanmar, this is at 2,000 RPM.

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o Since we already know that the optimum torque is at 2,100 RPM, you could say that you’d get the most bang for the buck out of this engine at 2,050 RPM — a combination of best fuel efficiency and most speed. o As for the curve of specific fuel consumption, this is inconvenient in more ways than simply converting grams per horse- power hour to sensible units such as liters per kilowatt per hour or gallons per horsepower hour. This isn’t because the conversion is difficult (it isn’t) but because almost every engine’s specific fuel consumption curve seems to understate the real- world, in-the- boat fuel consumption. o In practice, I’ve found that almost all diesel engines consume approximately 0.274liters per kW/hr . o For the 420 CX Yanmar, propeller output power at 2,300 RPM is 250 HP, so fuel consumption at this RPM (assuming the propeller is properly matched) is 220gms/kW, while at maximum 2,700 RPM fuel consumption is 230gms/kW. (The shape of the specific fuel consumption curve and its point of maximum and minimum consumption are usually quite accurate in service, just not the absolute consumption numbers indicated.) Determining Optimum Cruising Speed o So far, we’ve seen what the engine performance curves mean and that maximum oomph and fuel efficiency occur for this engine at between 2,000 and 2,100 RPM. Is this the proper cruising speed? Well, an argument can be made for this in terms of sheer efficiency, but it’d be a bit slow. In- stead, we can look at the performance curves to determine where the best compromise between efficiency and speed falls. In this case, 2,300 RPM looks like a good bet. At 2,300, torque is still high, specific fuel consumption is still low, and we’re getting a reasonable 250 HP at the propeller. Low cruise, for quiet, efficiency, and maximum range would be around 2,000 RPM, and you’d only open her up to 2,700 from time to time to show off or outrun a storm. o OTE: If you don’t have any engine curves available, you can estimate that the propeller power at various RPMs as follows: o 90% of max RPM = about 68% of max rated engine power o 80% of max RPM = about 48%; 70% of max RPM = about 30%; 60% of max RPM = about 22%; 50% of max RPM = about 15%; 40% of max RPM = about 11% o To determine the impact of adding a 9 kW high-efficiency BMG to the fuel consumption of the Yanmar 420 CX engine at cruising speed (2,300 RPM), we can follow these steps: Diesel Engine Efficiency at Cruising Speed o At 50% of maximum RPM, the engine is typically operating at a point of high thermal efficiency, near its sweet spot in the fuel map. o Engines are often most fuel-efficient between 40–60% of their maximum RPM and load capacity. o The increased load of a high power BMG improves the engine's brake-specific fuel consumption (BSFC) slightly, as diesel engines are generally more efficient under higher load conditions within their optimal range. o BMG Efficiency: Running the BMG at full load typically results in its peak efficiency (85%), minimizing losses in converting mechanical power to electrical energy. o Engine Efficiency Impact: Adding the BMG load increases the engine's total load, potentially pushing it closer to its optimal operating point, which can slightly improve overall fuel efficiency.

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Impact of BMG o Additional fuel consumption = 53.70 − 50.96=2.74 liters/hour.53.70 - 50.96 = 2.74 \, \(liters/hour}. o Percentage increase = (2.74/50.96) × 100 ≈ 5.4%(2.74 / 50.96) \times 100 \approx 5.4\%.Key Insights o The BMG load at maximum output has a minimal adverse impact on overall system efficiency at cruising speeds. o In some cases, adding the BMG load improves the fuel efficiency of the engine by moving it closer to its optimal operating range. o Adding a 9 kW BMG load to the Yanmar 420 CX engine at cruising speed increases fuel consumption by approximately 2.74 liters/hour or about 5.4%. o This is a relatively small impact, demonstrating the efficiency of using the BMG within the engine's cruising efficiency range. o There is no impact on boat speed because of the white space to propellor load.

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