May 14, 2025

Sun Odyssey 391 gets a 10kW power for overnight cabin aircon. There is no longer a 12V alternator!

Safiery’s hybrid retrofit system—featuring a 12kWh lithium battery, 10kW bidirectional motor generator (BMG), and Scotty AI controller

How is this possible to replace the 12V 120A Alternator with this power plant?

Safiery’s new Permanent Magnet Generator controlled by Scotty AI V3 and Solid State Lithium technology provides the perfect power and energy for sailing boats without a genset.
This is a 30Hp Yanmar 3JH engine. There is no need for a genset or excessive battery capacities.
This is a case of compact 48V power and lithium solution that fits hand in glove.
Charging the 12V starter battery AND powering all the 12V loads is done by Scotty AI DC DC functionality. In this boat up to 3kW can be provided at 12V.

Summary

The Safiery Bidirectional Generator produces up to 240A at 48V at 90% Efficiency.
Compare this to traditional alternators which produce from 100A to 160A at 70% efficiency.
A BGM is at it’s core a Permanent Magnet Generator which has rotor windings replaced by permanent magnets. Because there is no rotor excitation, 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.
A traditional alternator uses diodes and either an internal regulator to convert the AC power to DC or an external regulator like a Wakespeed.
The BMG has an inverter fitted to the rear that converts AC to DC and to control the speed and torque of the motor. The dynamic response of this inverter controller far exceeds an alternator.
The generator is 90% efficient. Compare that to 70% of an alternator.
The rear mounted compact inverter is 94% efficient. This out performs the common diodes in some alternators or the wakespeed remote regulator..
The Safiery BMG also uses HES Technology (Hybrid Excitation Synchronous). This combines permanent magnet (PM) excitation and electromagnetic excitation at the Stator (not rotor).
This hybrid excitation mechanism overcomes the limitations of low output power 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.

What role does Scotty AI play with the Bidirectional Motor Generator?

Big power needs to be handled securely and at high speed. Scotty AI V3 becomes an integral part of the power system with the BMG providing this functionality:
It communicates with CAN BMS lithium batteries and continuously calculates the charging parameters integrating these with the BMG control.
If there is no CAN BMS on the 48V lithium, then “no problem”. Scotty AI assesses non-CAN BMS lithium batteries and continuously calculates the charging parameters for the BMG to control.
Scotty AI controls the BMG power at different speeds so when a vehicle or boat accelerates from idle, the torque is relaxed to have less load on the engine.
Scotty AI controls the BMG based on temperature rise of the inverter, motor speed and torque to give smooth power across the range of engine RPM.
Scotty AI has an onboard DC DC to give maximum power when called for by high power 12V or 24V devices like winches.
Using the DC DC functionality, independent to the BMG, charges the same or an alternate 24V, 36V or 48V battery bank. The charging parameters can be completely different.
Using DC DC functionality, independent to the BMG charges the starter battery so only the BMG is present on the engine with NO 12V or 24V alternator.
Scotty AI V3 connects to the Victron VE.CAN bus with no negative impact to Victron control on the same bus.
Scotty AI V3 and the BMG is visible on Victron’s new GUI display showing the charging power in the “alternator” box.
SCOTTY AI V3 has a connected App that is used for tuning with a patented auto-tuning feature as well as setting up charging parameters for the BMG and DC DC independently.

Safiery’s Scotty AI controller and BMG now appear as an “Alternator” in the power production space on new Victron GUI

Comparison of BMG to Old School Alternator	48V 200A Bi-directional Motor Generator with Scotty AI (BMG)	Traditional 48V 130A Alternator with Wakespeed 500 remote field control.
Alternator Type	Hybrid Excitation Synchronous Generator (permanent magnets + hairpin windings)	Field-excited rotor only
Rotor Design	16 permanent magnets + excitation windings in stator	Field windings only
Power Density	1.65 kW/kg (advanced hairpin)	Lower due to round-wire winding
IP Level	Brushless Motor: IP25.	Generally Brushed
	Waterproof Inverter: IP6K9K	IP23 or lower
Dual Stator Design	Dual three-phase, 30¡ shifted	Single three-phase
Ripple Current Reduction	Significant (30¡ phase shift)	Higher ripple
Noise Vibration Harshness Performance	Optimized (low ripple and torque smoothness)	Higher NVH
Efficiency	Higher (permanent magnets + hairpin winding)	Lower (field-excited losses)
Fault Tolerance	Dual stator allows operation in partial failure	Single stator, no redundancy
Peak Generator Power	12 kW	6.2 kW
Efficiency	BMG is 90% Inverter Controller is 94%	60-70% (Less when hot)
Power at Idle (engine ~600RPM)	2-2.7kW	300-500W Typically
Continuous Power Hot	³7.0kW	5~7.0 kW
Maximum Speed	18,000 RPM	~8,000Ð10,000 RPM
Operating Temperature	-40C to 105C	-20C to 80C
Lifetime Expected	10 years, 300,000 km, 8,000 hrs	5-7 years, 150,000Ð200,000 km
12V, 48V Negative Isolation to Earth	Yes	No
Integration with Factory 12V or 24V Alternator	Full Integration for added power with Scotty AI DC DC	None
Load Dump Protection	100% load dump protection	Limited Protection as it depends on Battery notification before battery relay opens.
Automotive Safety ISO 26262 ASIL B	Compliant	Not compliant
Insulation Grade	Grade H (180¡C)	Grade F (155¡C)

Comparison	Safiery Bidirectional Motor Generator and Scotty AI V3	APS130*	APS 160*	Nations 8292HPX-100*
Alternator/ Motor Efficiency	90%	Not Published but estimate is less than 80%	Not Published but estimate is less than 80%	Not Published but estimate is less than 80%
Inverter Fitted and its Efficiency	94%	Uses Diodes which are low efficiency and External Field Current Regulator	Uses Diodes which are low efficiency and External Field Current Regulator	Uses Diodes which are low efficiency and External Field Current Regulator
Estimated Power Output at Engine Idle	3000W	Small	None	Small
Estimated Power cruising speed 1800 engine RPM	9000W	6000W	5000W	6000W
Maximum Output	11000W	6000W	7400W	6000W
Patented Auto-tuning	Yes	No	No	No
Limp Home Mode if CAN connection to Battery lost	Yes Set at 2kW	Yes Power level not published	Yes Power level not published	Yes Power level not published
Multipoint temperature Monitoring	4 temperature measurements	1 temperature measurement	1 temperature measurement	1 temperature measurement
Bidirectional 48-12-48 included	Yes at 1500W or 3000W at 12V	Requires separate DC DC	Requires separate DC DC	Requires separate DC DC
Isolated Negative	Yes	No	No	No

Sun Odyssey 391 gets a 10kW power for overnight cabin aircon. There is no longer a 12V alternator!

Safiery’s hybrid retrofit system—featuring a 12kWh lithium battery, 10kW bidirectional motor generator (BMG), and Scotty AI controller

How is this possible to replace the 12V 120A Alternator with this power plant?

Summary

What role does Scotty AI play with the Bidirectional Motor Generator?

Safiery’s Scotty AI controller and BMG now appear as an “Alternator” in the power production space on new Victron GUI

SAFIERY

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