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"Memory" effect in LFP batteries
Posted: Fri Oct 04, 2024 9:04 pm
by Andy
Here is something for those of you to consider with larger battery stacks.
https://nordkyndesign.com/practical-characteristics-of-lithium-iron-phosphate-battery-cells/
If you are short cycling with a pause after the shorter cycle then there is a memory effect. As the battery stacks get larger then the current draw per cell decreases and so from bits I have read elsewhere, it gets closer to the requirements for the memory effect..
It was not something that would have affected me in the past as the battery was never in a state of no charge/discharge.
I'm including a full charge every month in my code and also implementing my own float. So day to day I'll use 3.45V as 100% and then once a month boost to 3.55V per cell. I plan on stopping on the recommended tail current of .033C which is still 2.5kW
Re: "Memory" effect in LFP batteries
Posted: Fri Oct 04, 2024 9:57 pm
by AlBargey
Andy wrote: ↑Fri Oct 04, 2024 9:04 pm
Here is something for those of you to consider with larger battery stacks.
https://nordkyndesign.com/practical-characteristics-of-lithium-iron-phosphate-battery-cells/
If you are short cycling with a pause after the shorter cycle then there is a memory effect. As the battery stacks get larger then the current draw per cell decreases and so from bits I have read elsewhere, it gets closer to the requirements for the memory effect..
It was not something that would have affected me in the past as the battery was never in a state of no charge/discharge.
I'm including a full charge every month in my code and also implementing my own float. So day to day I'll use 3.45V as 100% and then once a month boost to 3.55V per cell. I plan on stopping on the recommended tail current of .033C which is still 2.5kW
Yeah Nordkyn has some really interesting info, but I've not read much about memory effect and I assume calendar ageing will be more an issue than memory effect.
0.033C is the older manufacturers test standard to 3.65v if you're only charging to 3.45v then 0.009C would be the recommended termination current on the older data sheets or if they're based on the newer 0.05C standard then 0.014C @3.45V.
https://nordkyndesign.com/charging-mari ... ery-banks/
Re: "Memory" effect in LFP batteries
Posted: Fri Oct 04, 2024 10:10 pm
by Andy
AlBargey wrote: ↑Fri Oct 04, 2024 9:57 pm
Andy wrote: ↑Fri Oct 04, 2024 9:04 pm
Here is something for those of you to consider with larger battery stacks.
https://nordkyndesign.com/practical-characteristics-of-lithium-iron-phosphate-battery-cells/
If you are short cycling with a pause after the shorter cycle then there is a memory effect. As the battery stacks get larger then the current draw per cell decreases and so from bits I have read elsewhere, it gets closer to the requirements for the memory effect..
It was not something that would have affected me in the past as the battery was never in a state of no charge/discharge.
I'm including a full charge every month in my code and also implementing my own float. So day to day I'll use 3.45V as 100% and then once a month boost to 3.55V per cell. I plan on stopping on the recommended tail current of .033C which is still 2.5kW
Yeah Nordkyn has some really interesting info, but I've not read much about memory effect and I assume calendar ageing will be more an issue than memory effect.
0.033C is the older manufacturers test standard to 3.65v if you're only charging to 3.45v then 0.009C would be the recommended termination current on the older data sheets or if they're based on the newer 0.05C standard then 0.014C @3.45V.
https://nordkyndesign.com/charging-mari ... ery-banks/
I had wondered what it would be at 3.45. That's some great info and answers that question nicely for me. I have seen a few posts alluding to quite bad degradation due to the memory/bump effect or whatever you want to call it. I think it is more of a problem for people who do a partial charge and walk away. e.g boat owners.