If you are looking for a cheapest and the simplest Li-Ion charger circuit, then there cannot be a better option than this one. 1) Simplest Li-Ion Charger using a single MOSFET If you don't have an auto cut-off, simply restrict the constant voltage input to 4.1 V.
LITHIUM BATTERY PULSE CHARGER FULL
The charger should have an auto-cut off at the recommended full charge level.(Typically this can be = Voltage 14% higher than printed value, Current 50% of the Ah value, lower current than this will also work nicely, although charging time will increase proportionately) Use an input supply which has a fixed current and fixed voltage output, as discussed above.So What does the Graph Basically Suggest? The supply must be automatically cut off as soon as the cell reaches 4.2 V level. Remember, although the graph shows the cell being charged even after it has reached 4.2 V, that's strictly not recommended during practical charging of a Li-Ion cell. Stage#4: In situations where the cell is not used for long periods, a topping up charging is applied from time to time, wherein the current consumed by the cell is below 3% of its Ah value. The SoC of a cell or battery is the optimal charge level which it has attained after a course of full charging, and this level shows the actual level which can be used for a given application.Īt this state we can say the cell condition is ready to use. Once this happens, the input supply is switched OFF and the cell is allowed to settle down for another 1 hour.Īfter one hour the cell voltage indicates the real State-Of-Charge or the SoC of the cell. Stage#3: As the current drops, it reaches its lowest level which is lower than 3% of the cell's Ah rating. The charging current is indicated by the RED dotted line. This drop in the current rate continues for the next couple of hours. Stage#2: In stage#2, the charging enters the saturation charge state, where the voltage peaks to the full charge level of 4.2 V, and the current consumption begins dropping. The 0.25 V is only for indicative purpose, an actual 3.7 V cell should never be discharged below 3 V. Stage#1: At the initial stage#1 we see that the battery voltage rises from 0.25 V to 4.0 V level in around one hour at 1 amp constant current charging rate. The following graph suggests the ideal charging procedure of a standard 3.7 V Li-Ion Cell, rated with 4.2 V as the full charge level. The following explanation will help to understand this better. It's actually an extremely friendly form of battery, and will get charged with minimal considerations, although these minimal considerations are essential and must be followed without fail.Ī few critical but easy to implement considerations are: auto cut-off at the full charge level, constant voltage, and constant current input supply. Does Charging a Li-Ion Battery Require Complex Considerations?Ībsolutely not. In tropical summer conditions, even this rate can turn into an unfavorable rate for the battery due to the existing high ambient temperature. A 0.5C rate is therefore considered as a standard recommended value.Ġ.5C signifies a charging current rate that's 50% of the Ah value of the battery.
Having said this, it is never advisable to use this extreme rate, as this would mean charging the battery at highly stressful conditions due to increase in its temperature. This is termed as charging at 1C rate, where C is the Ah value of the battery.
Unlike, lead acid battery, a Li-Ion battery can be charged at significantly high initial currents which can as high as the Ah rating of the battery itself. Basic Facts about Li-Ion Chargingīefore learning the construction procedures of a li-Ion Charger, it would be important for us to know the basic parameters concerned with the charging Li-Ion battery.
LITHIUM BATTERY PULSE CHARGER PROFESSIONAL
Although Li-Ion batteries are vulnerable devices, these can be charged through simpler circuits if the charging rate does not cause significant warming of the battery., and if the user does not mind a slight delay in the charging period of the cell.įor users who want rapid charging of the battery, must not use the below explained concepts, instead they can employ one of these professional smart designs.