We’ve been putting on quite a few test drive miles in combined city/highway driving mode. The improvement with the new motor has been astounding! It now has the power to completely move the vehicle down level grades at 50+ mph (i.e. the gas engine idles while the electric motor does all the hard work). This has allowed us to see results of over 40 mpg as verified by both actual gas consumption and the onboard fuel efficiency gauge. We’ve found that the onboard gauge generally registers a bit higher fuel efficiency than reality in gas-mode only and shows a low reading with the hybrid system active.

The current supply chain issues have presented some challenges in getting parts we need. We ordered a custom, more powerful motor almost 6 months ago and it finally arrived. With the machining of a modified axle bracket, it’s now installed. The anticipation is that this motor will be able to fully power the vehicle while driving at speeds of 50+ mph. The previous motor wasn’t able to get all the way there – the gas engine had to provide some level of assist. This previous system topped out at about 30 mpg for combined city/highway driving. It remains to be seen just how much better this motor allows the system to get in terms of fuel efficiency.

The new system which includes many of the latest improvements is ready for installation. The following pictures show the process.

Several of the new pieces are coming together. Some pictures to show the progress:

One of the key pieces in the Unleash system is the throttle interceptor. This device intercepts the connection from the onboard vehicle computer (powertrain control module or PCM) and the throttle pedal. It needs to intercept this so that the electric assist can be given priority over gas operation. There are several ways the electric assist can be proportioned, but the way our system is usually set up to operation is to have the first 0-10% of the throttle movement command 0-100% of the electric system and the remaining 11-100% of pedal travel to command 0-100% of the gas system. This way, when you’re cruising down the road at 50 mph and the pedal might be at 8% (for example), the electric motor is doing all the work moving the vehicle down the road and the gas engine is simply idling.

There is a cable that connects to the vehicle high speed CAN bus to get several important pieces of information such as shift selector position, rpm, and vehicle speed. It also is able to relay to the throttle interceptor information about button presses in the vehicle which allows us to use the volume control buttons on the steering wheel to adjust the electric assist level (when the radio is off). Feedback can be provided by a speaker on the throttle interceptor that can make various sounds/pitches.

Here’s a view of the latest revision of throttle interceptor. Normally, the unit would have epoxy potting compound covering the circuitry. But this view shows the various components. This device mounts under the dash just above the throttle pedal. It uses cable assemblies that use stock vehicle connectors so no modification is required to the vehicle wiring making it easy to both install and remove and eliminating the chance for installer error.

Another important piece of the system is what we call the alternator interceptor. This device intercepts the connection going from the PCM to the alternator. It has another CAN bus connector that ties into the Unleash system. The alternator interceptor’s job is to trick the onboard computer into thinking that the alternator is functioning correctly when the Unleash system takes over powering of the 12 volt system. The alternator interceptor sends the correct signals to the alternator to shut if off when this is taking place. This is one of the nifty ways that the Unleash system is able to maximize fuel efficiency by removing every possible load from the internal combustion engine (ICE).

Just a quick update to show the new active BMS boards as well as the battery module heating boards. The heating serves two purposes. Of course, one of those is to heat the modules in really cold weather. Performance is affected when temperatures drop substantially. With the vehicle usually plugged in, it’s easy and effective to provide some amount of heating to counteract the performance degradation effects. These customized heater boards are able to provide about 120 W of heating. The other purpose though is to aid in high-power balancing of the battery cells. There is a string of heating elements (power resistors) that is switched on to an individual battery cell. This is our own patent-pending technology that serves the purpose of both heating and high-power cell balancing. Our custom active balancing boards have cell-by-cell active balancing. But in addition, there is this additional ~20 W per cell for passive balancing. Typical passive balancing systems are not even a couple watts. This combined active/passive balancing system allows us to very aggressively perform a patented technology that we license which gives a substantial improvement in battery pack life.

A 12 volt monitoring circuit was recently added as a feature to the system. The power pack has four high power 12 volt connectors. These are for:

  1. Connection to the vehicle 12 volt system at the battery
  2. Connection to the power pack’s DC-DC converter that provides power to the 12 volt system from the high voltage battery pack to alleviate the need for power to come from the alternator while the battery pack has a charge
  3. Accessories that run on 12 volts like a high power inverter. This one is intended for on-board devices although it can also be routed to external 12 volt loads.
  4. Offboard 12 volt loads such as a RV.

However, the power pack needs to be able to monitor the 12 volt system so external loads (like an inverter or RV) cannot drain the truck’s 12 volt battery once the high voltage power pack has been fully discharged.

So today was a machining day for the new prototype bus bars. Also, since some modifications needed to be done to the baseplate, it was a good opportunity to throw an Unleash logo on the underside!

With things learned from the initial prototype, work has progressed on several improvements/revisions. Two of the important pieces of the system are the power pack controller and the battery management system active balancing boards. With the schematic and PCB designs completed, they were then fabricated. Next up will be testing.