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RC Battery Charger

RC Battery Charger

It is in the best interest for everyone in RC to get the most out of their LiPo batteries and do so while being safe. For a first time user this can be quite intimidating.

There are a few key items that will be covered here to explain some important points. The operation of your charger using these points should be covered in the instruction manual for your specific charger as all chargers are slightly different.

RC Battery Charger – LiPo Balancer

The first thing one may want to do is to understand how you are to balance your LiPo battery pack. Some chargers have a Balance port built in while others have a stand alone unit. Either way will get the job done. A balancer is necessary for RC LiPo batteries. The balancer will make certain that each cell in a LiPo pack will remain at the same level of voltage. This ensures that each cell is also at the same charge level. If one cell were to be at a higher voltage, this cell may go over the maximum voltage for a cell. It is recommended to always use the balancer with the instructions given from the manufacture for each charge cycle. It is recommended to balance the packs with every charge.

Understanding LiPo Charge conditions based on cell values.

Lithium Polymer cells have a nominal voltage of 3.7v per cell. An absolute minimum voltage of 3.0v and a maximum voltage of 4.2v. Your charger is designed, in most cases, to prevent a charge from occurring if the cell voltage is below 3.0v and to stop a charge when the voltage reaches 4.2v at 0A. During the course of a charge cycle, the voltage will rise at a constant current. If the battery were charging at 2.5A and voltage was 4.0v/cell the charger would continue to charge at 2.5A until each cell measures 4.2v.This would be termed constant current charging. At the first instance of 4.2V per cell, the cell is not 100% charged. The charger will change its charging pattern by applying what is called constant voltage charging. The charger will slowly reduce current by keeping the voltage constant at 4.2v. The charge rate will drop to 0A, in which at this time charge is complete.

Values to Program in RC Battery Charger

It’s important to set these values correctly. Two common values that must be put in to a charger is current(sometimes in mAh) and LiPo pack nominal voltage. It’s very easy to determine these values. LiPo pack voltage will be determined and often placed on the pack itself, by taking the number of cells and multiplying by 3.7v. For example a 4s pack would have a nominal voltage of 14.8v. This value of 14.8v would typically be entered in to a charger or in some cases 4s LiPo representing 4 cells in series. The second value to be entered is the charge rate. It has been common for 1C charge rate across the board and some chargers will accept the cell capacity for charge rate. This assumes a 1C charge. For example, if one were to want a 2C charge, it would be neccessary to multiply the capacity of the pack by two and enter this value in to the charger. The other way to enter the value for some chargers is by entering the charge rate. The charge rate is commonly 1C but newer technology allows 2C, 3C and possibly even higher. If your pack is 5000mAh. 1C would equal a charge rate of 5A. 2C would be 10A and so on. Be certain to follow the manufactures recommendations on which rate to charge at. If unknown 1C is best.

RC Battery Charger Times

The higher the charge rate, the quicker the duration of charge. At a rate of 1C it will take just over an hour to charge a pack. Increasing the rate to 2C would half the time required and so forth. Just keep in mind maximum battery life may be achieved at the slower rate and be certain to follow the manufactures maximum recommended charge rate.