Symbioquine
Solar Enthusiast
- Joined
- Jul 6, 2021
- Messages
- 422
I do not mean to be rude or harsh, but there some a point where Nit Picking is pointless, especially when within the margin and trying to push beyond it. Honestly, you are NOT gaining anything by charging over 3.425Vpc / 27.4V.
As I already said;
I'm not trying to eek out every last watt of power, I just want a solid reliable system and a fairly detailed understanding of why it behaves as it does.
I do think that this inquiry in general still has both practical and educational value:
- If either of the prevalent hypotheses turn out to be true - bad connections or bad initial cell balancing - they could be important to resolve from a fire safety and a cell longevity perspective respectively.
- Most folks aren't going to have monitoring data like I have. Instead, they'll get tiny glimpses into similar behaviors with their multimeter and BMS. I think that it is useful to have some case studies where there is more detailed data that the system owner (me) and community have made sense of.
Brute statement.
IF you want the batteries to Settle to 3.400 when fully charged, do not exceed 3.510Vpc to full charge as LFP will ALWAYS DROP 1.0V average for settling within 1 hour. LFP Always Settles, no if's, and's or but's.
(I assume you mean 0.1V)
Past 3.450 your net gaining much of anything, other than quirks. At that level even with matched cells within 1.5milliohm difference will show their quirks and deviate. You can chase these issues for months and never get much further as your tickling the working edges. And you know what, even 30mv differential within a "working" pack is moot as that balances up after.
I think there must be a compromise between your statement and what I'm doing here. I take your point about diminishing returns beyond threshold X, but I'm also leery of just throwing my hands up, writing "here be dragons" on the map, and losing the opportunity to understand my system better. Particularly, where understanding my system better might involve uncovering real problems like bad connections/balance.
In pursuit of a solid reliable system, I'd like to be able to say "I've tested and understood how it works within spec up to threshold X so I'm going to operate up to 0.90X in normal usage."