Choosing a right battery charger is important to lead acid batteries, because a proper battery charger not only protects batteries from overcharging but also prolongs battery life. On the other hand, using a wrong battery charger to charge batteries may result in the following consequences: a too-large battery charger will have negative influences on the battery’s lifespan; a too-small battery charger will require long charging time. So, how should the right battery charger be chosen, the following will help make an appropriate selection.
Charger Category
There are two basic types of battery charger: 2-STAGE and 3-STAGE chargers. The 2-STAGE chargers are developed for frequently/fast charging applications, such as portable equipment, electric scooter, electric motorcycle, etc. The 3-STAGE chargers are for fixed/cyclic charging purposes, suitable for UPS, emergency lighting equipment, etc.
Limit on Battery Charging
A high charging current could damage the battery or shorten its life. As a result, battery manufactures have strict instructions on how high a charging current is allowed. A normal recommendation is that the charge rate should be between 10% and 30% of the battery’s capacity, i.e. a 20 Ah (ampere-hour) battery should be charged by 2 ~ 6A.
Selection
Follow the steps below when selecting a battery charger.
| Step 1: Identify the capacity of the battery you need to charge | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| a. | Battery’s voltage and capacity can be found on the battery label located on the top or side of the battery. (If you are unable to find this information, please contact the manufacturer.) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| b. | When multiple batteries are used,Batteries in series: total VBat = NxVBat (volts) total CPBat = CPBat (Ah)Batteries in parallel: total VBat = VBat (volts)total CPBat = NxCPBat (Ah)(Suppose VBat is battery voltage, CPBat is battery capacity, and N is number of batteries) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Step 2: Identify the charger type you need in your application | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| a. | For recharging a discharged battery to a normal condition: 2-STAGE charger. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| b. | For maintaining a fully charged battery or charging a battery operated along with loads: 3-STAGE charger. (Green-colored region) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Step 3: Check the table | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| This is MW’s suggestion. It’s highly recommended to consult your battery manufacturer for the limitation of the max charging current. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Example: Two lead-acid batteries in parallel are used in an UPS application, how to choose a suitable charger for charging them? | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Specification of the batteries | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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1) The voltage is 12V; the capacity is 80×2 = 160Ah. 2) 3-STAGE charger is suitable for UPS applications. 3) Referring to the table, PB-230-12/PB-300-12/PB-360-12/ |
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Conclusion
Choosing the right battery charger can ensure that batteries are charged efficiently and accurately. Moreover, the right one can also reduce the charging time without damaging or overcharging them.