Which hybrid should I buy in Zimbabwe?

Taurayi Raymond Sewera

HYBRID VEHICLES use two sources of propulsion power — the internal combustion engine (ICE) and the high-voltage battery pack/rechargeable energy storage system (RESS).

The system on strong models like the Toyota Aqua Hybrid, Toyota Axio Hybrid, Toyota Prius, Honda Fit Hybrid GP5, Honda Fit Hybrid GP6 and Honda Shuttle Hybrid GP7 will use the RESS or ICE, or both sources of propulsion, depending on the mode of operation as follows:

Electric launch (0-16km/hr) — No engine start (100 percent electric)

Low speed operation (16-48km/hr) — Electric (75 percent) + Engine (25 percent)

Mid speed operation (48-80km/hr) — Electric (50 percent) + Engine (50 percent)

High speed operation (80km/hr and above) — Electric (5 percent) + Engine (95 percent)

Now, the hybrids we are importing into Zimbabwe are “used” or “second-hand” vehicles, and some models are from 2012 and 2014.

These vehicles are being discarded in countries like Japan because the high-voltage batteries have depleted and require replacement, according to the manufacturer specifications.

What is now happening is that, because the high-voltage battery is no longer capable of contributing the propulsion power as it is supposed to during the different modes of operation, the engine will now try to compensate for the lost power from the RESS.

The engine in a hybrid car is not designed to produce a lot of power, as it does not need to.

It is designed to work together with propulsion power from the high-voltage battery pack or RESS, depending on the operation modes.

The ICE is more efficient on high revolutions per minute (RPM), and, on the other hand, the e-machine driven by the high-voltage battery or RESS is more efficient on low RPM during city driving, etcetera.

The high-voltage battery packs on these “used” hybrid vehicles we are importing in Zimbabwe and Africa at large are compromised due to ageing (they have already done the eight years or 150 000km that the manufacturers warrant).

Honda Vezel Hybrid

Unfortunately, this means the engine is going to try and compensate for the “lost” power that the RESS is supposed to contribute, thereby causing the engine to operate using the maximum fuel it can, which translates to lower mileage per gallon than designed.

A hybrid with a depleted high-voltage battery pack will no longer serve its purpose of saving fuel and lower emission output.

Now that we know what conditions these hybrids are coming with, we can talk of which one is better than the other.

We start with the “Toyota Family”, in the form of what we are currently importing in Zimbabwe.

The Toyota Aqua Hybrid, Toyota Axio Hybrid, Toyota Prius C Hybrid, Toyota Prius Gen II Hybrid and Toyota Prius Gen III Hybrid, among others, use nickel metal hydride (NiMH), which has disadvantages compared to lithium family battery packs on the Honda Vezel, for example.

The disadvantages that the NiMH has is apparent capacity loss (ACL), also known as “memory loss”.

When left non-operational, the NiMH battery will self-discharge at a rate of 20 percent in the first 24 hours.

After that self-discharge, the cell/cells will continue to discharge at a rate of 10 percent a month until completely discharged.

Considering the time these used cars wait in warehouses in Japan, in addition to the time it takes to ship them to Zimbabwe, the RESS arrives with very low capacity and high ACL.

That is why on most of them, the high-voltage system warning light will start showing after a few months, if not weeks.

Based on the RESS issues, the “used” Toyota family hybrids we have in the country seem to lack the needed propulsion power.

On the other hand, “used” Honda family hybrids in the form of the Honda Fit GP5 Hybrid, Honda Fit GP6 Hybrid, Honda Shuttle GP7 Hybrid, Honda Vezel Hybrid, et cetera, come with the lithium iron phosphate, lithium nickel manganese cobalt and many other similar battery types that do not have the ACL that comes with NiMH.

Major issue with “strong” Honda hybrids

The major challenge with the hybrids mentioned above is the transmission.

The Honda hybrids mentioned above come equipped with a dry dual clutch transmission, which uses electro-hydraulic clutch actuators to operate the clutch, as well as an electric shifter to move the gears using hydraulic fluid actuation in the form of brake fluid Dot4.

Honda Fit Hybrid

Because brake fluid is hydroscopic, which means it absorbs moisture, over time, if left unserviced, the water will accumulate to a point of compromising the brake fluid boiling point and damage the sealed/unserviceable dry dual clutch assembly.

Now, the customer needs to replace the transmission with a new one, which sells for around US$4 700. Even though the lithium battery packs
mentioned above have longer life, they will still need to be maintained before the cells deplete prematurely.

In the next instalment, I will discuss in-depth the high-voltage battery family architecture. I will also talk about how to maintain different types of these high-voltage battery packs so that we can prolong their longevity.

 *Taurayi Raymond Sewera is ASE and Auto Care 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, and ACDC-certified Master Hybrid and electric vehicles technician. He is the founder and CEO of TauRay Automotive. He can be contacted on: +263772341193, +263772357296 or [email protected]