Your car battery has gone bad and you’re getting slow acceleration from your car. Hence, it’s pretty normal to wonder if the bad battery is the culprit here.
So, you want to know can a bad battery cause slow acceleration?
Yes, a bad battery can cause slow acceleration. A dead 12V aux battery can cause slow acceleration in cars running on fuel. A bad motor battery, in contrast, can cause slow acceleration with no fuel in the tank. Finally, a full EV will have slow acceleration at the high speed of a bad motor battery.
Seems confusing, right? Well, we’ve explained everything you need to know in the later sections.
Can A Bad Battery Cause Slow Acceleration?
A bad battery can cause many issues in your car including slow acceleration and power steering failure.
However, there are many types of cars with different running mechanisms available on the market.
The following table summarizes the effects of bad batteries on different types of cars.
| Car Type | Can The Battery Cause Slow Acceleration? | |||
| When Run on Fuel | When Run on Battery | |||
| Bad 12 Volt (Auxiliary) Battery | Bad Electric Motor Battery | Bad 12 Volt (Auxiliary) Battery | Bad Electric Motor Battery | |
| Gasoline-Powered Cars | Yes(When the battery fails to power the spark plug or the EFI) | N/A | N/A | N/A |
| Diesel-Powered Cars | Yes(When the battery fails to power the CRDi) | N/A | N/A | N/A |
| Hybrid Electric Vehicles (HEV) | Yes(When the battery fails to power the spark plug or the EFI) | No | No | Car has fuel: No (the engine will kick-in).Car has no fuel: Yes (At high speed until the battery dies & the car stops). |
| Plug-in Hybrid Electric Vehicles (PHEV) | Yes(When the battery fails to power the spark plug or the EFI) | No | No | Car has fuel: No (the engine will kick in).Car has no fuel: Yes (At high speed until the battery dies & the car stops). |
| Mild Hybrid Electric Vehicles (MHEV) | Yes(When the battery fails to power the spark plug or the EFI) | No | N/A | N/A |
| Battery Electric Vehicles (BEV) | N/A | N/A | No | Yes(At high speed) |
As you can see, the battery affects the acceleration when the car uses the battery to run. However, the story doesn’t end here.
As we’ve mentioned earlier, even fully fuel-powered cars can have slow acceleration for bad batteries. But it happens only in extreme situations, of course.
But why does this happen? Let’s explore them in detail.
Can A Bad Gas-Powered Car Battery Cause Poor Acceleration?
Usually, a bad gas-powered car battery cannot cause poor acceleration. This is because gas-powered cars run on gas.
Hence, the batteries in those cars have no connection with their acceleration. Rather, the batteries are there for only functioning electrical operations.
But, here comes the twist. Some of those electrical components have relations with engine performance. Those are-
- Electronic Fuel Injection (EFI)
- Spark Plug
Let’s explain it a bit further.
The battery in gas-powered cars starts your car and provides currents to other electrical components. The alternator, in contrast, works to recharge the battery while the engine is running.
The battery and the alternator are dependent on each other. A bad battery can put extra loads on the alternator. Similarly, a bad alternator can drain the battery faster than usual as well.
So, if the battery goes completely bad, the alternator will struggle to power all the electrical components.
Eventually, the EFI or the spark plug may fall short of power and cause slow acceleration.
So, that was about gas-powered cars. But what about diesel-powered cars?
Can A Bad Diesel-Powered Car Battery Cause Poor Acceleration?
Usually, a bad diesel car battery cannot cause poor acceleration. The reason is the same as for gas-powered cars.
But unlike gas-powered cars, diesel-powered cars don’t even use spark plugs. Hence, you don’t need to worry about the spark plug falling short of power either.
However, most modern diesel engines use CRDi to electronically inject the fuel. So, there’s still the risk present of the CRDi falling short of power.
But what if your diesel engine car has a carburetor rather than CRDi? Well, you won’t face any acceleration drop in your car from the dead battery.
Now, let’s find out how a bad battery affects the acceleration of a hybrid car.
Can A Bad Hybrid Car Battery Cause Poor Acceleration?
A bad hybrid car battery can cause poor acceleration. And, this applies to both, the 12V aux battery and the electric motor battery.
However, there are different types of hybrid cars and their mechanisms are different as well.
Let’s have a quick glimpse of how different types of HEVs work.
| Hybrid Types | Can Run on Only Battery | Can Run on Only Fuel | Can Run on Fuel & Battery Simultaneously |
| Full Hybrid (HEV) | Yes | Yes | Yes |
| Plug-in Hybrid (PHEV) | Yes | Yes | Yes |
| Mild Hybrid (MHEV) | No | Yes | Yes (only for a short-term boost to the fuel-engine) |
As you can see from the table, hybrid cars can usually use both fuel and battery to run. And, they’re engineered in a way that you won’t notice the seamless alteration of the power source.
As you now have the basic idea of hybrid cars’ operation, let’s dive deep into each category.
Can A Bad HEV Battery Cause Poor Acceleration?
A bad HEV battery can cause poor acceleration when the car runs on the battery.
However, this will only happen if the car has no fuel. This is because the fuel engine should immediately kick in whenever the HEV battery goes bad.
But if there’s no fuel, you’ll get slow acceleration at high speeds until the battery completely dies. Eventually, your car will be stalled.
That was for the HEV motor battery. But what happens if the 12V aux battery dies in your HEV?
A dead 12V aux battery can contribute to a lack of power to the spark plug or the EFI. If this happens, the electric motor will kick in immediately.
However, the electric motor can’t provide as fast acceleration as the fuel engine would at high speeds. As a result, you’ll get slow acceleration in your HEV.
Source: MIDTRONICS
HEV motor batteries generally are smaller (8 kWh on average) compared to PHEV’s. And for the smaller battery size, the electric motors are smaller as well.
So, when the fuel engine stops, the HEV will be using only the motor battery to run In that case.
As a result, it will drain the motor battery soon. Eventually, the motor battery will be completely discharged and can’t move the car at all.
So, that was all about the full hybrid car battery impact on acceleration. Now, let’s move on to the PHEVs.
Can A Bad PHEV Battery Cause Poor Acceleration?
The story for a bad PHEV motor battery remains the same as the HEV motor battery.
But, the motor battery in PHEV is comparatively bigger (15 kWh on average) than the HEVs. And, the motor itself is bigger as well.
As a result, this bigger motor can provide enough acceleration if the spark plug or EFI fails. In addition, the bigger battery will drain much slower than the HEV battery.
However, a bad motor battery will cause slow acceleration at a speed over 70km/h. We’ve discussed this in detail in the later section.
Now, let’s find out how MHEV behaves with a bad battery
Can A Bad MHEV Battery Cause Poor Acceleration?
MHEV motor battery is the smallest (1kWh or less) among all the hybrid cars. The tiny motor like the battery in MHEV is only for assisting the fuel engine. The electric motor alone can’t run the car for even an inch.
Hence, it behaves almost like fuel powered car.
So, that was all about the hybrid car. Now, let’s dive into fully electric cars.
Can A Bad EV Battery Cause Poor Acceleration?
A bad EV battery can cause poor acceleration at high speeds. You won’t notice the acceleration drop at lower speeds because of the motor’s characteristics.
Source: MOUNTAINPASS PERFORMANCE
A dyno test on Tesla shows that you won’t notice any acceleration drop until you reach 70 km/hr.
However, the acceleration drops after 70km/h with the charge level of the battery.
Tesla Model 3 Performance Dyno Test – Will it work on a hub dyno?
The lower the State of Charge (SoC) goes, the greater the acceleration drops at high speed.
So, if you’re facing slow acceleration at high speed, the motor battery should be the culprit here.
But what about the 12V aux battery in BEV? Does this battery affect acceleration like fuel-engine or hybrid cars?
Well, the answer is no here. This is because there’s no spark plug or EFI involved in fully electric cars.
Hence, a bad 12V aux battery can’t cause slow acceleration in BEVs.
But is a bad battery the only component that causes slow acceleration in a car? Let’s find out.
What Can Cause Slow Acceleration In A Car?
As we’ve already discussed about the battery, we’ll focus on the other factors here.
The below table summarizes the most common factors that can cause slow acceleration in your car.
| Factors | Solutions |
| Clogged Air Filter | Clean the air filter and replace it if necessary. |
| Bad Spark Plug | Clean the spark plug and replace it if necessary. |
| Clogged Fuel Filter | Clean the fuel filter. |
| Clogged Oil Filter | Clean the oil filter and replace it if necessary. |
| Clogged Exhaust | Contact a mechanic to check the exhaust and clean it if necessary. |
| Bad Timing Belt | Replace the timing belt as soon as possible. |
| Dirty Throttle Body | Clean the throttle body. |
| Worn Out Clutch | Contact a mechanic to replace the clutch plate. |
| Sensor Problem | Contact a mechanic. |
| Other Errors | Contact a mechanic. |
The table above lists the most common issues that can cause slow acceleration.
However, there are endless numbers of factors that can cause slow acceleration. These include worn-out piston rings, wrong valve clearance, neutral gear, and so on.
Most of these issues require professional knowledge to work on. So, we recommend consulting an expert if the factors in the table aren’t the culprits.
FAQs
What Issues Can a Bad 12V Car Battery Cause?
A bad 12V car battery can cause the car not to start. Along with that, it can cause your car electrics and electronics to lose power. Furthermore, your car’s push start/stop function may fail. Finally, it can completely stall the car failing to supply current to the spark plug & the EFI.
What Issues Can a Bad Car Motor Battery Cause?
A bad motor battery in hybrid cars can cause higher fuel consumption. This is because the engine needs to work extra to power the car and recharge the battery. A bad battery in an EV, in contrast, can cause low torque and power at high speed.
Can a Bad Battery Affect Engine Performance?
A bad battery directly doesn’t affect the engine performance. However, a completely dead battery may fail to power the spark plug or other electrical sensors. In that case, the bad battery will affect engine performance indirectly.
Conclusion
That was all about your query on can a bad battery cause slow acceleration. We tried to cover and explain the topic from every angle possible.
Hopefully, the content was helpful.
Let us know if we’ve missed anything in the comment.
