Slow charging vs fast charging


Nowadays, many electrical equipment such as portable energy storage, and RVs are equipped with lithium batteries. There are basically two methods when them: slow charging vs fast charging. The charging speed of lithium batteries is closely related to charging power, battery charging characteristics and temperature.

So the question is, what is the essential difference that slow charging vs fast charging of lithium batteries? What impact will the difference in charging time between the two have on battery life?

1. Is fast charging suitable for lithium batteries

Lithium batteries are divided into different types, generally lithium-iron phosphate batteries and ternary lithium batteries. The former is suitable for slow charging, and the latter is suitable for fast charging.

It depends on the manufacturer's design of the battery performance. Its charging performance is determined by the internal settings of the charger, which cannot be changed. Each lithium battery manufacturer will configure the ports of slow charging vs fast charging according to the battery characteristics. The BMS system will uniformly manage the charging process. As long as charging is carried out in accordance with the manufacturer's requirements, it is safe.

Lithium-iron phosphate batteries and ternary lithium batteries

Generally speaking, lithium batteries cannot fast charging by using original chargers. If the fast charging station is of pulse type, it will cause damage to the protective plate of the battery and easily cause the protective plate to malfunction. If the lithium battery protection board is broken, there will be big problems. The chemical composition of lithium batteries is different from that of lead-acid batteries. Lithium batteries require constant voltage and constant current two-stage charging.

The charge and discharge rate of a lithium battery refers to the charge and discharge current within the unit rated capacity. For example, when a battery with a rated capacity of 100Ah is charged and discharged at 20A, the charge and discharge rate is 0.2C. Generally, the charging current of lithium batteries is set between 0.2C and 1C. The larger the current, the faster the charging, but at the same time, the battery heating phenomenon will be more serious.

Fast charging of lithium batteries saves charging time, but may cause greater damage to the lithium battery itself. Due to the polarization phenomenon in the battery, the maximum charging current it can accept will decrease as the charge and discharge cycles increase. According to the analysis of electric vehicle lithium battery manufacturers, a series of problems such as reaction decomposition of electrolyte and gas production have suddenly increased the risk factor, which will affect the safety of lithium batteries and the life of non-power batteries will inevitably be greatly shortened.

Abnormal Battery Heat

Generally speaking, lithium battery chargers can be made according to charging requirements, but whether lithium batteries can be fast charged depends on whether the lithium battery manufacturer allows it, because some lithium batteries are not allowed to be fast charged. Therefore, about slow charging vs fast charging, you must understand it clearly first to avoid problems.

2. What are the dangers of fast charging of lithium batteries

  • The installation requirements and costs of lithium battery charging equipment are high. Because the high current and voltage, and the impact on the battery is greater in a short period of time. Long-term rapid charging affects the life of the lithium battery;
  • Fast charging will input a large current into the lithium battery in an instant. Frequent use of fast charging mode will reduce the battery’s recovery ability and reduce the number of battery charge and discharge cycles;
  • Fast charging has high requirements for the quality of lithium batteries, which will greatly damage the battery life and the safety factor will be significantly reduced, so do it as little as possible when it is not necessary;
  • The working principle of lithium battery fast charging is: The first is to increase the voltage, and the second is to increase the current current. So a large amount of current will cause the battery plate to react at an excessive speed. This reaction generates large amounts of heat due to internal resistance and exceeds limiting temperature values, thereby damaging or prematurely aging the battery.
Lithium-battery charging equipment

3. Slow charging vs fast charging

Slow charging vs fast charging of lithium batteries, which are relative concepts.

Generally, fast charging is high-power DC charging, which can fully charge 80% of the battery capacity in half an hour. Slow charging refers to AC charging, and the charging process takes 6 to 8 hours.

The reason why fast charging is fast is due to the difference in charging voltage and current. The larger the current, the faster the charging. When it is almost full, switch to constant voltage, which can prevent the lithium battery from overcharging and also protect the battery.

The charging current and power of slow charging of lithium batteries are relatively small, which is better for battery life, and the charging cost is low during low power consumption. Fast charging will use larger current and power, which will have a great impact on the battery pack and also have an impact on its lifespan. Fast charging also requires supporting equipment, such as converting AC to DC, which increases the cost.

Cycle life of the battery

It should be noted that continuous use of fast charging will have an impact on the life of the lithium battery. The cycle life of lithium batteries is certain. When using slow charging, the cycle life of the battery can usually reach more than 3,000 times. However, if it is always fast charging, the cycle life will be shortened to about a thousand times, or even lower. So slow charging vs fast charging are important to batteries life.

4. FAQs about battery charging

① When is the best time to charge

When to charge can depend on battery usage. Under normal circumstances, it is most appropriate to charge when the remaining power is about 20%-30%. But don’t be too entangled and have to use 20%-30% of the power before charging. In actual use, if the remaining power is less than 50%, you can charge it reasonably as needed.

② How long shall we charge

It depends on the SOC of the lithium battery. It is best to keep the power of lithium batteries at around 20-85%. Charging time that is too short or too long will shorten the battery life, and in severe cases may even cause safety accidents. The "8 hours of charging" we often hear means that when the battery is completely discharged, some batteries take about 8 hours to fully charge.

Click on the picture for product details of Tycorun 12V 100Ah lithium deep cycle battery


③ Can't I charge it immediately after riding

Do not charge immediately after riding because the battery temperature will gradually rise during driving. Charging immediately after riding will not only damage the battery, but may even cause spontaneous combustion in severe cases. Under normal circumstances, you should wait at least 10 minutes after riding for the battery to cool down before charging. In summer, when the ambient temperature is high, the waiting time can be extended appropriately.

④ Do I need to charge regularly if it is not used for a long time

Storage at a loss of power has a great impact on the battery. The longer it is stored at a loss of power, the more serious the damage will be to the battery. If not used for a long time, the battery should be fully charged and stored in a ventilated and cool room. In summer, when the temperature is high, the self-discharge of the battery is high and the power is lost quickly. It is best to charge it once every 2 months. In other seasons, it can be charged once every 2-3 months.


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