• Have you tried out dark mode?! Scroll to the bottom of any page to find a sun or moon icon to turn dark mode on or off!

diy solar

diy solar

Overkill Solar BMS Settings

Donniesuits

New Member
Joined
Aug 19, 2020
Messages
18
Hello,

I have a 100ah LifePo4 battery with internal BMS. I am using Overkill Solar app to access the BMS. My first question is can someone show what the best settings are for each of the configurable settings. Screen shot is fine, then I can just copy those into my battery BMS.

Second question has to do with the cell capacity voltage. I have seen online on several websites as well as in the BMS specs that the values from 100% to 10% should be set starting at 3450mv and proceed down to 10% capacity set at 3215mv (see Screen shot). These are not accurate if you do the math, I have attached a spreadsheet that calculates the MV voltages from 100% to 0% based on cell voltages of min voltage 2500 and max voltage of 3450. If we are setting the full voltage at or around 3500mv and the low voltage and cut off at or around 2500 why would we not have a scale that represents this? Obviously, 3215mv setting for 10% capacity is no where near 10% if you have your low cell voltage set at or around 2500mv. 10% would be 2595mv. Should I change these settings to match what my table shows for each calculated drop in cell voltage?
 

Attachments

  • Calc Cell Percentage.jpg
    Calc Cell Percentage.jpg
    22.9 KB · Views: 29
  • IMG_1009.PNG
    IMG_1009.PNG
    148.8 KB · Views: 33
  • IMG_1010.PNG
    IMG_1010.PNG
    151.5 KB · Views: 30
show what the best settings
You need to change the balance settings,
Start volts 3400
Delta to Balance 15
Balance only when charging 'off'.

There is no point modifying the 'cell%cap voltages '. These are only used if the battery has not been cycled. Once the battery reaches cell full volts, (3500 with your settings), the BMS syncs to 100% SOC. There after uses Coulomb coulnting to compute the SOC .
If a protection event occurs , or you use the mos switches or protection values are modified, the BMS may use the 'cell%cap' to estimate SOC untill a sync to 100% occurs.
Your estimated relationship between cell volts and SOC is not correct. 3215 mV is a good value for 10% SOC .Screenshot_20231111-180015_Chrome~3.jpg
Graph provided by a experienced forum contributer, hope it's OK to reproduce here.
 
Last edited:

diy solar

diy solar
Back
Top