dreuge
New Member
- Joined
- Jan 18, 2021
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- 12
The "Cell Self-Discharge Rate" is a parameter setting for the capacity configuration of a JBD BMS like Overkill/LLT SP04S020 (4S 120A LiFePO4 BMS). The iOS app gives the unit as a "%", but it is a rate so it should have a per unit of time. For example, ∆C/C is the percent change in capacity, so a precent discharge rate should be ∆C/(C*∆t). The SP04S020 BMS default value is "0.2%". The Overkill BMS manual just states, "3.2.5 Discharge Rate: Leave this at default setting."
My guess is that "Cell Self-Discharge Rate" is a "Daily Cell Self-Discharge Rate". I read somewhere that after 3 months, prismatic cells maintain ~95% SOC. So after some further search, I came across the EVE LF280 spec sheet which lists a reference to "Charge Retention at RT" giving "Capacity Retention >= 95%" after 30 days. This implies that "Cell Self-Discharge Rate" <= 5% per 30 days or (5%)/( 30 days) = 0.17% per day.
So if I understand this correctly, "Cell Self-Discharge Rate" = ∆C/(C*∆t) <= 0.17% per Day. Does this make sense? Does anyone have a good understanding of this?
In addition, does the BMS use this value to calculate/estimate a drop in capacity due to self-discharge?
My guess is that "Cell Self-Discharge Rate" is a "Daily Cell Self-Discharge Rate". I read somewhere that after 3 months, prismatic cells maintain ~95% SOC. So after some further search, I came across the EVE LF280 spec sheet which lists a reference to "Charge Retention at RT" giving "Capacity Retention >= 95%" after 30 days. This implies that "Cell Self-Discharge Rate" <= 5% per 30 days or (5%)/( 30 days) = 0.17% per day.
So if I understand this correctly, "Cell Self-Discharge Rate" = ∆C/(C*∆t) <= 0.17% per Day. Does this make sense? Does anyone have a good understanding of this?
In addition, does the BMS use this value to calculate/estimate a drop in capacity due to self-discharge?
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