Precautions for connecting lithium iron phosphate battery packs in series and parallel:
1. Do not mix lithium iron phosphate battery packs of different brands, different capacities, or new and old lithium-ion batteries. Choose batteries with consistent performance. Replace all batteries when their charge is low. When using lithium-ion battery packs in series, use batteries of the same type. Pay attention to the battery polarity; if even one battery is installed with reversed polarity, it will reduce the voltage of the entire battery pack, not increase it.
2. If lithium-ion battery packs of different capacities or new and old batteries are used together, leakage and zero voltage may occur. This is because during charging, the capacity difference causes some batteries to be overcharged while others are not fully charged. During discharging, some high-capacity batteries are not fully discharged while low-capacity batteries are over-discharged. This vicious cycle damages the batteries, leading to leakage or low (zero) voltage.
3. Generally, when lithium iron phosphate battery packs are used in series and parallel, lithium-ion battery cells need to be matched. The matching standards are: lithium-ion battery cell voltage difference ≤ 10mV, lithium-ion battery cell internal resistance difference ≤ 5mA, and lithium-ion battery cell capacity difference ≤ 20mA.
4. Remove the lithium-ion battery pack protection circuit board and check whether the battery protection board can be used in your series or parallel circuit. For example, if the previous protection board was 4.2V, and you connect it in series to make it 8.4V, then the battery protection board can no longer be used.
