Voltage Difference
Many customer send me one picture as below when they DIY the lifepo4 Battery pack , or they they need to charge the Battery . This is one Nigeria customer who buy 8pcs Lifepo4 Battery from me
then ask me how to do . why it is like that
Let’s explain the voltage Difference
1 what’s the voltage Difference
Typically lithium battery packs consist of multiple cells connected in series. For example, A 60V lithium iron phosphate battery pack has 20 cells in series, while NCM lithium battery pack has 17 cells in series. The voltage difference between each cell or between cells in a series , We called the voltage difference. Ideally, all cells in a series should be fully charged, discharged together without any difference;.this is the best state. However, over time and with the increase ,in the number of cycles, The slight will changes something in each cell.
There are many reasons for the generation of Voltage differential. These could include abnormalities in the battery’s roller, copper deposition at the positive electrode, crystallization in the negative electrode material, or electrolyte imbalances. and if the wire is loose when you connect the series battery . It is very common in DIY Lifepo4 Battery pack. especially the customers from Africa because of local contions
2) The type of voltage Difference
like what we have mentioned as above ,when it is under the different situation , it will be different type, that is the Static voltage difference and Dynamic voltage difference
2.1 Static Voltage difference : when the device is fully charged/stabilized, then left Them to stand for 30 minutes to 2 hours without charging/discharging or any load .
- IT will Reflect the self-discharge, capacity inconsistency, and minor internal defects of the Battery.
Most People DIY Lifepo4 pack, when they finish the production , they will test it or during the making , when they charge the battery full. they will test the voltage. , This action will do many time ,. when they dont have enough conditions to test . it is the simplest and direct way to test the battery .
2.2 Dynamic Voltage Difference: It means the Real-time voltage difference when the Pack is under the high loading ,charging or discharging, speeding or Climbing
IT wil reflects: internal resistance difference, polarization, and load-carrying capacity. The dynamics can more accurately reflect battery health for the NM lithium Battery pack.
When the rider use the lifepo4 battery all day ,if he finds something wrong , the first action is to open the Blue tooth to check, if there is something wrong with the voltage from the SMART BMS .
Pls note :
Differential voltage is an important indicator of battery pack consistency, but it is not the unique indicator of battery pack quality.
Generally, the smaller the differential voltage, the more stable for the battery pack performance , and its lifespan will be longer. However, differential voltage does not fully represent the battery’s safety and aging level. For example, when we has used one lifepo4 Battery pack 3-5 years, It may have a small differential voltage, but the battery pack has already aged to a certain extent.
3) How to check the voltage difference in a Lifepo4 Battery pack
Lifepo4 Battery are clearly rechargeable batteries.we need the increase the voltage for them
The highest charging voltage for a single string is 3.65V, the Fixed voltage is 3.33V .The lowest Fix voltage is 3.0V . Below 3.0V , There isn’t any Electricity . The protection voltage is 2.5V, The voltage difference of a LIFEPO4 battery is generally considered to be the voltage difference when it is depleted. Lithium iron phosphate ( LFP) batteries cannot exceed 50 millivolts
between 3.33-3V,The voltage difference at the terminals of an LFP battery pack is crucial . so the static voltage difference of an LFP (lifepo4 )battery pack is generally assessed. IT means the voltage difference after complete discharge. So when Factories produce the lifepo4 batteries pac , they will typically discharge the batteries and allow them to rest for a period of time , then check their self-discharge and consistency before manufacturing the battery packs. After manufacturing, then will do the aging tests , then conducted to ensure the quality of the battery packs.