Micro-hybrid technologies and internal combustion engines

We currently have various types of hybrid vehicle technologies here in Zimbabwe that include the popular Toyota Aqua hybrids, Toyota C-HR hybrids, Honda Fit GP5 hybrids and Honda Vezel hybrids, just to mention a few.

One of the first hybrid vehicles that was adopted in large numbers was the Honda Fit Gp1, which falls in hybrid category of “mild hybrids”.

Micro hybrids use a technology called Start-Stop Technology (SST), like the one found in Mazda i-Stop.

The start-stop system is simply one that shuts off the engine when the vehicle is at a stop for an extended period of time.

When the vehicle is stopped and the engine is shut off, the vehicles are powered by the auxiliary battery, which means for a vehicle with start-stop technology to operate this system efficiently, the auxiliary battery has to be healthy.

The start-stop technology was introduced to increase the longevity of the internal combustion engine (ICE) within an automotive application, and also to increase fuel mileage.

This type of application must manage the power present in two 12-volt batteries (the auxiliary battery and the start-stop system batteries) to make sure the power available can provide the needed cranking voltage to crank the engine.

Monitoring the power is usually done with an energy management system that determines when the engine needs to operate, so the battery can be charged.

This system maintains both batteries in the vehicle, along with managing electrical devices on the vehicle.

Depending on the original equipment manufacturer (OEM) application, this system can have a plethora of different names.

When the vehicle is stopped for an extended period of time, the power control module (PCM) will command the engine to turn off.

Starting the ICE in a quick way requires increased energy capacity to provide enough cranking amperage, without the driver “feeling” vehicle operational differences.

The ability to perform a vehicle start-up and take-off from a stop situation, without a large delay, is crucial to driver comfort and safety.

To increase these starting requirements, the OEMs employ one of three different systems:

• Dual 12-volt absorbed glass mat (AGM) battery system
• Direct current-to-direct current (DC-DC) system that utilises a power supply transformer
• Ultracapacitor (UC) system that provides power boost for restart

Power capacity has to be increased to support the simultaneous start of the engine and the uninterrupted operation of the vehicle electrical system.

These additional components will increase the initial cost of the vehicle, and the cost of maintenance and repair.

Starting the ICE multiple times in one trip requires a robust electrical system to keep up with continuous restarting process.

Power storage in a capacitor or multiple batteries requires certain diagnostic procedures to verify proper operation.

There are many vehicles with the start-stop technology on the roads in Zimbabwe, but have no signage on the body that shows the vehicle is a hybrid.

As long as the vehicle switches off the engine during a vehicle extended stop period, it means it has a certain type of start-stop system and that puts it in the hybrid vehicle category.

The start-stop system that uses cranking battery system strategy saves anywhere from 3 percent to 10 percent of the fuel that a normal vehicle would consume.

This is based on the amount of idle time that the vehicle would have conducted in its normal operation routine.

This strategy works well in stop-and-go traffic in a large urban area, where there is a lot of traffic congestion.

 

Because this system is using operational strategy adjustment, the needs of the conventional 12-volt battery are similar to those of a conventional ICE-powered vehicle on the road today.

The introduction of the AGM battery has helped further the life of the lead acid technology-based 12-volt battery.

The AGM has glass mat within each cell that hold the electrolyte in place, and prevent it from being affected by sloshing or vibration within the vehicle.

With this type of battery design, the battery can provide bursts of power when desired.

The design of this type of battery also allows for resistance to temperature variations, while still maintaining proper voltage output.

Over the lifetime of this battery, it can provide over three times the amount of starts as a conventional flooded lead acid battery.

Overcharging harms this type of battery when compared to a flooded lead acid technology, so the charging system must have precise control to eliminate the possibility of over or under-charging it.

The start-stop system that utilise ultra-capacitors allows for nearly instantaneous levels of inrush current to the cranking motor to happen quicker than a battery-powered system.

Unlike conventional capacitors, ultra-capacitors can store 10 to 100 times more energy per unit mass or volume, compared to traditional electrolytic capacitors.

These capacitors are dual-layer electrolytic capacitors with larger plates than a conventional capacitor.

Additionally, the number of capacitor charge and discharge cycles are significantly high, and it can operate in wide temperature ranges without affecting its ability to store or transfer energy.

Therefore, the life expectancy of a capacitor is significantly longer than a typical electrochemical battery.

For start-stop systems that utilise 12-volt auxiliary operating battery to operate correctly, the vehicle must maintain the electrical load desired by the driver when the ICE is turned off at a stop.

This includes operating the heating, ventilation and air-conditioning (HVAC) and power windows, etcetera.

 

*Taurayi Raymond Sewera is ASE & Autocate Association certified World Class Master Technician with 39ASEs, ASE Advanced Level Specialist L1, L2, L3 and L4, AMI Accredited Master Electric Vehicles and Master Automotive Manager, ACDC certified Master Hybrid and Electric Vehicles Technician. Taurayi is the founder and CEO of TauRay Automotive. He can be contacted on +263 77 234 1193, +263 77 235 7296 or [email protected]