One question we get repeatedly is “Can I top balance at 3.7V?”
The reason for this question is that many DC power supplies have a minimum voltage adjustment range of 0.1V. It is impossible to set the voltage to 3.65V. The only option is to top balance with 3.6V or 3.7V.
This gives rise to two concerns.
- whether the battery cells will not reach true top balance if they are charged with 3.6V.
- if 3.7V is used for charging, the maximum rated voltage of the battery cell is exceeded, and whether this will damage the battery cell.
Here, we recommend using 3.6V for top balancing when your DC power supply cannot be set to 3.65V.
While 3.7V over the rated maximum voltage of 3.65V for LiFePO4 battery cells is not too high, it is, after all, over the limit. Although it will not necessarily cause damage to the LiFePO4 battery cells, there is always a risk.
For LiFePO4 battery cells that we plan to use for more than 5 years, we need to take this risk out of the equation.
So is charging with 3.6V enough to bring LiFePO4 battery cells to top balance?
The answer is yes, 3.6V is enough to bring LiFePO4 cells to top balance. According to the charging curve of LiFePO4 battery cells, when the battery cells are charged to 3.4V, the voltage rises very fast, and by 3.6V, the curve has also reached the rightmost part near the vertical end. The SOC(State of Charge) is close to 100% at this point.
The correct way to top balance LiFePO4 using 3.6V
In general we recommend the user to operate like this.
1, Connect LiFePO4 battery cells in parallel and charge them with 3.4V or 3.5V.
2, Continuously monitor the voltage of the battery cell. And fine tune the charging voltage to 3.6V when the voltage rises to 3.4V or 3.5V.
3, pay close attention to the change of charging current, when the current gradually decreases to close to 0. disco
4, (OPTION) charge again with 3.6V and observe the current. If the current is close to 0, it means the top balance is done. If the current is not close to 0, you will also observe that it drops quickly. When it drops close to 0, disconnect and leave it for some more time.
After the above steps, the SOC of the battery cell is over 99.9%. In fact it can already be seen as achieving top balance.
Finally, you can connect the battery cells in series and form a battery pack with BMS. In the future, the BMS will balance all the cells without interruption to maintain the efficient output of the whole battery pack.
Any question and inquiries please send email to firstname.lastname@example.org, we answer quickly.
Since 2019, as long-life, deep-cycle lithium iron phosphate (LiFePO4) cells begin to be used in solar energy storage and the price of solar panels continues to fall, more and more homes are installing…
In post “How to Quickly Identify Fake LFP Battery Cells Part 3 – QR Code“, we introduced the way to parse the QR code on the LiFePO4 battery cells. According to the rules of QR code parsin…
EVE deep cycle lithium iron phosphate(LiFePO4) battery cell are mainly applied into RV/boat/solar energy storage station system. Using them you can easily set up your own 12V，24V，48Venergy storage sys…
How to calculate battery pack power? For DIYers planning to build a solar energy system, determining solar panel power and battery pack power is the first step. The most cost effective battery pack so…
With LiFePO4 battery cells becoming available in the retail and wholesale markets, DIY LiFePO4 battery packs are starting to become more and more popular. For users who are trying to DIY LiFePO4 batte…
We created this battery power consumption calculator to make it easy for you to calculate the battery life. You may be planning to DIY a battery pack using the LiFePO4 battery cells we provide. This c…