Why hybrids aren't efficient when traction battery nears end of life

Hybrid cars are highly sought after in the market due to rising prices of petroleum products. They have their advantages over internal combustion engine cars.

Hybrid cars are known for fuel economy as they take advantage of regenerative braking to charge the hybrid battery in synergy with the internal combustion unit (ICU). Regenerative braking is not enough to charge the battery, so the internal combustion engine also charges the battery through the motor/generator when there is demand for charge.

Unfortunately, this advantage begins to fade as the battery progressively becomes weak.


What makes the hybrid battery to charge?

As mentioned earlier, there are two sources of charge for the hybrid's high voltage battery.

1. Charge from regenerative braking

The braking system does not rely on the use of brake pads alone to stop the car.

Regenerative braking works in such a way that when the speed of the car is not very low nor a very sudden stop is required, the motor/generator attached to the wheel converts the kinetic energy at the wheels to electrical energy used to charge the battery. Let's look at how this works with a very simple explanation. When you turn the shaft of an electric motor, it supplies current and voltage at its electrical terminals. Now, place an electrical load at that terminal and the shaft will require more force to turn it. This means that load which is the battery that is being charged in the case of a hybrid car is turning the motor to a brake. It is because of regenerative braking that the brake pads of these cars last way beyond that of the non-hybrid counterparts. The pads are idle sometimes during braking.

2. Charge to the hybrid battery from the internal combustion engine

The engine that is powered by gas also charges the hybrid battery when the charge depletes. This is why the system is designed in such a way that the ICU kicks in when the battery needs charge and turns off when the battery is charged.


Why hybrid cars fuel consumption increase when the battery is weak

Before you continue reading, you may wish to see symptoms of weak high voltage battery of hybrid car.

As earlier said, the battery depends on the ICU for charge. The increased fuel consumption happens in two ways.

1. When the hybrid battery begins to age, the demand on the ICU to charge the battery increases. This translates to more frequent running of the ICU. The more the engine kicks in, the more fuel that it uses. 

2. A weak battery draws more charge current. Due to this, the engine works harder to charge the battery and this causes use of extra fuel.3. A weak battery might take a longer time to charge and a very short time to discharge. The energy used during that long charging time is simply wasted. Whether it charges for a long time or not as it happens in some situations, the energy used to charge the battery is wasted as the battery does not hold significant charge anymore.

If the high voltage battery is not replaced on time as it begins to become weak, the car becomes a money pit as spending on gas increases. Thankfully, hybrid batteries have been known to last an average of ten years, so this does not make a hybrid car a bad choice.