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Join date: Nov 10, 2022

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Homemade 24v battery lithium require at least 7 18650 batteries in series (in a series). If large-capacity 24v battery lithium are needed, multiple series can be connected in parallel (7 batteries in a series).




The nominal voltage of an 18650 battery is 3.7V, but when we directly measure the voltage of an 18650 battery, we get 4.2V. Many netizens who want to make their own 24v battery lithium cannot make up their minds. Should they connect 6 18650 batteries in series or 7 18650 batteries in series?




In fact, we directly measured the voltage at both ends of the 18650 battery, is no-load voltage (4.2V), once the load is added, the voltage will rapidly decrease, and with the longer discharge time (battery power reduction), the voltage will gradually decrease. The following figure is the voltage curve of 18650 battery under different discharge current (Note: different brands of 18650 discharge voltage curve will be different, the following figure is for reference only).




As can be seen from the discharge voltage curve of a single 18650, if the calculation is based on 4.2V for a single battery and six batteries are connected in series, the battery voltage is less than 21V for half of the time. This means that the inverter (or appliance) will go into protection when your battery pack gives off about 3/4 of its power, which means that you'll only be able to use about 3/4 of the power in a 24V lithium battery made from six 18650s.




Therefore, in order to maximize the battery capacity, a series 18650 battery is needed, that is, the number of batteries needed is calculated according to the nominal voltage of 18650. The official nominal single section voltage takes into account the load and drop voltage.

tom lee

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