What Causes False Voltage in Car Batteries?
4 Answers
The following are the reasons for false voltage in car batteries:1. Display Issue: Electric vehicles display battery level based on the corresponding relationship between load current and voltage. When the vehicle starts or climbs a slope, the load current increases, causing the voltage to drop, which results in a sudden decrease in the displayed battery level. This is why the battery level may drop by 1-2 bars instantly when climbing a slope. Once the slope is finished and the load current returns to normal, the voltage also recovers to its normal level, making the battery level appear to return.2. Cadmium-Free Batteries/Cadmium-free batteries have lower initial voltage and are prone to sudden power drops during acceleration: Older batteries contained cadmium, which enhanced conductivity, reduced internal resistance, improved discharge voltage, and provided better performance in extreme temperatures and during charge-discharge cycles. After 2014, due to environmental protection initiatives, cadmium-free batteries were promoted, which slightly affected battery performance. The initial voltage became lower, leading to sudden power drops during acceleration.
I've been driving for over a decade, and the most common cause of weak battery voltage is battery aging. Over time, the internal plates become sulfated and crystallized, which is equivalent to increased resistance. The voltage may appear high on the surface, but the actual available energy is very low. Another factor is insufficient charging, such as frequent short-distance driving where the alternator never gets a chance to fully charge the battery, or when the alternator itself malfunctions. Extreme weather also plays a role—cold winter temperatures can drastically reduce battery performance, while summer heat accelerates internal aging. I've also noticed that if the battery lacks water or gets contaminated, its internal condition becomes even more unstable. It's important to regularly check battery health, ideally using a multimeter every six months to measure the actual voltage or getting a professional diagnosis at a repair shop. Don't wait until you have trouble starting the car to regret it—timely replacement can save a lot of hassle.
Last time my car wouldn't start. The dashboard showed normal voltage but lacked power. The mechanic called it 'phantom voltage'. The main issue was internal battery aging or sulfation - those crystalline deposits on electrodes obstruct normal current flow, making output voltage appear normal while actual power supply is weak. Also, if you only take short trips frequently, the engine doesn't charge the battery long enough to reach full capacity, easily creating this illusion. External factors shouldn't be ignored either - in winter or consistently hot regions, battery performance naturally degrades. I've noticed many overlook the importance of regular maintenance. I recommend checking battery condition during every service, especially for vehicles over three years old. Avoiding excessive use of electrical devices after turning off the engine can also extend battery life.
I think a weak battery voltage is like an aging phone battery, showing full charge on the surface but dropping quickly when in use. Most of the time, it's because the battery has been used for a long time, leading to increased internal resistance, or it has been deeply discharged before, damaging its internal structure. Short-distance driving can also result in insufficient charging, causing the voltage to appear high but actually unable to sustain startup. Here's a simple way to prevent it: regularly take long drives to allow the alternator to fully charge the battery, and check the battery terminals for cleanliness every few months. If you experience difficulty starting in winter, it's best to preheat the car or upgrade the battery model. This is much more cost-effective than emergency repairs.
