Battery reserve capacity - things you may like to know

Definition of battery reserve capacity

Generally speaking, the reserve capacity of a battery represents the amount of time a fully charged battery can operate at a voltage not lower than a specific voltage. If you need a battery for long-term sustained loads rather than short-term bursts, it is particularly important to understand this.

The battery reserve capacity is a crucial indicator in measuring its reliability. Batteries can have strong starting ability, but poor reserve capacity. Battery reserve capacity refers to the discharge time of a battery at a constant current of 25A when the electrolyte temperature is 25 ℃, until the 12V battery drops to 10.5V.

Reserve capacity is commonly referred to as RC, which refers to the time (in minutes) that a 12V battery can operate before the voltage drops to 10.5V. It is measured in reserve minutes.

The importance of battery reserve capacity

Backup capacity is used to understand how long the battery can be used under continuous load. It is very important to know whether you plan to discharge for a long time, as this is a good indicator of battery performance. If you know the backup capacity, you will have a better understanding of how long the battery can be used and how much power can be utilized.

There is a big difference between whether your backup capacity is 150 minutes or 240 minutes, which can completely change the way you use batteries and how many batteries you may need. For example, if you fish on the water all day, you should know the battery level and usage time so that you can effectively schedule your travel time and go home without running out of battery.

Depending on how you plan to use the battery, such as for days long RV trips or occasional golf carts, you will have different reserve capacity requirements but a long lasting battery is always a good choice.

Battery reserve capacity in different batteries

The reserve capacity directly affects the amount of electricity you can generate using the battery. Since power is equal to the product of current and voltage, if the battery voltage drops from 12V to 10.5V, the power will decrease. In addition, since energy is equal to power multiplied by the length of time used, if the power decreases, the generated energy will also decrease. If the reserve capacity of the battery is 150, it means that it can provide 25 amperes of current for 150 minutes before the voltage drops to 10.5V.

Compared with 12V 100Ah lead-acid batteries, the average reserve capacity of 12V 100Ah lithium batteries is about 240 minutes, and the average reserve capacity of 12V 100Ah lead-acid batteries is about 170-190 minutes. Lithium batteries provide higher reserve capacity at the same Ah rating, and lead-acid batteries have an average reserve capacity lower than lithium batteries. This is because the reserve capacity of lead-acid batteries decreases as the discharge rate decreases. Therefore, when choosing batteries, installing lithium batteries instead of lead-acid batteries can reduce space and weight.

Battery reserve capacity is different from ampere hour (Ah), as reserve capacity is only a measure of time, while ampere hour measures the amount of amperes or current that can be generated within an hour. You can calculate reserve capacity in ampere hours, and vice versa, as they are related but not the same thing. When comparing the two, the reserve capacity of a battery more accurately measures how long it can be used under continuous load compared to ampere hours.

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