Scotty 3kW Bi Directional DC to DC 12V to 24,36,48V
SCOTTY IS AN INNOVATIVE PRODUCT THAT
- Is 12V on low side and 24, 36, 48V on the high side. It is bi-directional
- Drives a DC to DC converter to extract power from an alternator (12V or 24V) WITHOUT changing the alternator regulator
- When extracting power from an alternator, Scotty monitors the alternator temperature and voltage to ensure that the alternator is not "over worked" and that the power demand is not pulling down the vehicle voltage. In this way, the vehicle is always given priority and there is no impact on vehicle warranty.
- When extracting power, Scotty has a sophisticated Lithium battery charging feature.
- When the alternator and starter battery are combined, the bi-directional feature of Scotty will reverse the power flow in 20ms and deliver power back to the starter battery (and 12V or 24V network)
- Scotty also has a traditional alternator regulator in-built to drive an alternator through the field drive and charge the same battery voltage as the alternator directly
- The case is billet machined to manage heat.
- It is rated to 3,000W. That’s 250A at 12V, 125A at 24V, 60A at 48V.
System Architecture Examples:
12V vehicle alternator: Scotty to 24V or 48V lithium. Bi-directional running 12V devices in vehicle/ canopy, 12V high current winch. There is no other 12V battery other than start battery.
48V vehicle alternator: Scotty to 12V chassis of vehicle to charge starter battery and run vehicle loads (up to 250A). 48V Alternator charges 48V lithium battery directly. Safiery have 100A or 150A 48V Alternators (5kW to 7.6kW). There is no other 12V battery other than start battery.
12V outboard alternator(s): Scotty charging 24V, 36V or 48V lithium. This is popular with trolling motors at 24V or 36V and the house lithium is maintained at the higher trolling motor voltage. Bi-directional running 12V devices in boat, 12V high current windlass. There is no other 12V battery other than start battery. A Multiplus II 3000 Inverter can operate on the LS.
12V marine engine alternator: Scotty charging 24V or 48V lithium. Bi-directional running 12V devices in boat, 12V high current windlass. There is no other 12V battery other than start battery.
ADDING SECOND ALTERNATOR: SPRINTER, SILVERADO, RAM, FORD F TRUCK OR FORD TRANSIT FOOD VAN:
- Second alternator is 12V as a standalone alternator or combined with primary alternator: Scotty to 24V or 48V lithium. Bi-directional running 12V devices in vehicle/ canopy, 12V high current winch. There is no other 12V battery other than start battery. This configuration generally gives higher power at idle.
- Second alternator is 48V as a standalone alternator: 48V Alternator charges 48V lithium battery directly. Safiery have 100A or 150A 48V Alternators (5kW to 7.6kW). Scotty also at the same time extracts power from the primary alternator at up to 3000W. In this configuration, one Scotty will produce up to 11,000W of power at 48V. Bi-directional running 12V devices in vehicle/ canopy, 12V high current winch. There is no other 12V battery other than start battery. This configuration generally gives higher power at idle.
HOW CHARGING LITHIUM BATTERIES FROM THE ALTERNATOR WORKS:
1. Bi directional DC to DC converters have Low Voltage Side and High Voltage Side. We can them Voltage “Pins”.
2. When the alternator voltage reaches a specified trigger point for the Low Voltage Pin, power will be extracted to the high side pin automatically. While extracting power, demand may cause the low side voltage to drop yet it will continue.
3. The high side pin has set point voltages to charge lithium batteries. At first it will be a Constant Current Bulk/Acceptance Charge followed by a Float Voltage. The parameters and “expert mode” is set by the CANbus Integrated Controller.
4. Battery charging demand on the high side is met by the alternator power either until the power is at a maximum or until it cannot meet the power required any more, at which time, the Low Side voltage will decrease.
5. When the voltage decreases to below the low side set point, the power flow to the high side stops and may reverse direction if programmed to do so.
6. That is it. Using voltage as the primary electrical switching function makes it so simple and reliable. No VSR, No Shunt!
HOW THE BI-DIRECTIONAL FEATURE WORKS:
1. When the engine and therefore alternator is turned off, the voltage at the starter battery will slowly drop.
2. Once this drops below the Low Side trigger point for the Low Voltage pin, power will flow to the low side pin automatically.
3. This means there is no need for a 12V house battery. The starter battery provides a 12V base. Power effectively bypasses it and goes straight to the low side loads. Typically these are 12V devices like fridge, water pump and lights.
4. However, when it comes to using a winch, Scotty is out on it’s own. A 14,000lb winch requires around 350-400A at 12V. Running the vehicle alternator can deliver , say 150A on an LC200. Scotty will deliver 250A to the 12V pin which gives a total of 400A for the winch. Combined with a 250A Alternator, a total of 500A is deliverable to a winch.
5. To protect the starter battery in the event that the High Side battery is depleted, a smart battery protect is installed to ensure the starter battery never goes flat.
THE BILLET MACHINE CASE IS IMPORTANT.
The Case is critical to performance. Scotty “stops” at a base plate temperature of 100C. Without the billet machined case absorbing and emitting heat, the unit reaches 100C at 2,500W in less than 8 minutes. The carefully designed billet machined case extracts heat and transfers it to surrounding environment. When environment is at 20 degrees C, 2,500W can be sustained indefinitely with a max temp of 87 degrees C.
CORRECTLY SIZED AND PLACED WIRING IS CRITICAL.
New comers to Safiery and Scotty installs have to remember we are dealing with high power flows in both directions. In a Toyota LandCruiser 79 series for example, the standard alternator fuse in the vehicle main link fuse assembly is only 140A . Yet up to 250A may pass back to the battery from Scotty. Having adequate sized cables and fusing in place is essential and common sense. There is no impact on the vehicle’s power system with a properly wired and fused system. The vehicle’s demand for power always has a priority as Scotty operates with a voltage sense wire to ensure that the specified vehicle voltage is always maintained.
A QUICK RECAP ON FUNDAMENTALS OF ENERGY MANAGEMENT FUNCTION IN SCOTTY:
For Euro 6 engines and vehicles using the starter battery as a very mild hybrid.
- These vehicles drain the starter battery down when idling and under load until the starter battery reaches around 70-75% SOC measured by a coulomb counter on the battery negative post.
- As a result, using this stored energy to reduce engine load reduces fuel consumption. On top of this, if this is done when fuel efficiency is poorest, there is an added boost to fuel economy.
- These vehicles then replenish this energy when the vehicle is in “regenerative” mode of either braking or coasting and the EFI control is off.
Bidirectional DC to DC Specs
- Charges a low side (12V) battery from either 24V, 36V or 48V at 3000W at over 95% efficiency.
- Charges or assists the high voltage (24V, 36V or 48V) battery at 3000W at over 95% efficiency.
- Enters “Pre-charge” mode when the 48V battery has additional external charging (like solar controller or inverter/charger).
- Ruggedized design with 8mm thick aluminum baseplate with 5mm powder coated steel cover.
- Designed to meet MIL-STD-810G for harsh shock and vibration environment
- Compact size of only 220 x 150 x 25 mm.
- Light-weight at only 1.3kgs with a low-profile design
- Efficiency up to 97%, one of the highest power densities available.
- Operational temperature range is -40˚C to 100˚C.
- Safety disconnect switch for charging from or to the 12V battery.
- reverse voltage protection, short circuit protection, as well as low standby current for the low side.
Two-Way Operation at 3,000W
Constant Current Mode and Direction Selection
The charger operates as an ideal current source with variable direction when the output voltage is lower than the voltage specified by the CAN interface. This configuration allows energy transfer between the 12v and 48V. The 12V current can be programmed in the range of 1A-250A. The charger has an internal soft start to reduce inductive voltage drop in the power cables during both turn-on and turn-off. The charger will not operate if the current is set to zero or it is outside the limits. Charging current level can be changed on the fly.
- The direction of the current can be changed dynamically during operation. In that case, the charger will shut down and change the mode of operation through the internal soft start thus eliminating surge current during the direction change.
Safiery use an embedded CANbus controller with interface for complete control of the charger, as well as monitoring the current and the internal temperature.
The following functions are fully controlled via CAN interface:
- Current and voltage set points
- Current direction
- Protection threshold: Under-voltage, Over-voltage and Over-temperature
- In addition, the 12-48V Hybrid CANbus Charger provides low side current monitoring and internal PCB temperature monitoring.