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LiFePO4 Voltage Settings guide for BMS, Chargers and Loads

LiFePO4 Voltage Settings guide for BMS, Chargers and Loads 2022-04-09

To get the document, click on the orange
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button at the top of the page.

All the voltage settings in the BMS, Loads and Chargers can be daunting to figure out. This paper attempts to explain the various settings, how they relate to each other and how to choose them.

Click on the orange 'download' button for the document

A big shout-out to @Dzl for helping develop this resource.

As with all of the resources I create, reviews, comments, suggestions and corrections are always welcome.

A nice related resource from @SteveS :

General LiFePO4 (LFP) Voltage to SOC charts/tables


Note: This resource is a duplicate of the resource of the same name in the 'Beginners' resource Section. This resource is linked to the same download file.

4/9/22 Update:
Added section discussing Accumulation Phase cut-off current and added appendix with a link to a good video from the Off Grid Garage channel.
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FilterGuy
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thank you
I think your LifePo4 graph is wrong and mixed it up with Li Ion. No graph on the net is this high of voltage as you show the curve to 4.2 volts and low to 2.5. Most LifePo4 shows 14 % which is right at the lower knee at ruffly 3.18 volts. Your graph shows almost 3.38 at 14% and this is definitely wrong.
FilterGuy
FilterGuy
Funny.... the graph shown was taken from the net.

2.5V to 4.2V are the extreme limits of discharge and charge without immediate damage on LiFePo4. There is little reason to push the cells to these limits because they are well past the knees of the curve and the last .5V-.75v past each knee adds very little additional storage.

The bulk of the storage is obtained between 3.3V and 3.6V and most people will set their system up to be within that range. The most aggressive use will operate pretty close to these values, but a lot of people like to set things significantly less aggressive than this in order to prolong the life of the batteries. The key is to set the chargers and load to typically operate in your preferred range and set the BMS (2nd line of defense) at values that are outside the range of the Chargers and Loads but still within the 2.5V - 4.2V range. (if the system is working properly, it will never hit the BMS values). The trick is to set the BMS range as conservative as possible, but far enough outside the Charger/Load range to avoid unnecessary trips of the BMS.
Does exactly what it says on the tin. Perfect.
The chart mentions "if you can't disable float completely". Might be good idea if it is better to disable float to specifically state to do that.
Nice documentation for charging LFP! I will be using this information.
Thanks
Thank you for your very useful information! It's really helpful.
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