DaveinOlyWA wrote:i dont think its outrageous to have a temporary loss in extreme temps which does happen in cold and hot. i do not have access to 21 Kwh in winter like i do in Summer. i tested that theory twice. once before the GID, once after and the results were probably temp related since i got access to just over 19 Kwh once and just under 19 Kwh the 2nd time. so the winter hit is less performance and less capacity.
so to have the same but to a lesser degree for Summer i can believe. problem with that i see. it would appear that a portion of the summer loss is permanent and likely to be cumulative.
i expected to have at least 5% after a year and up to 10% degradation after 18 months. i thought there would be a big chunk lost at first (still do) and then it would taper off to 1-2 % a year ending at 20% after 5
so could have been
year 1; 10% lost
year2-5 2% lost total 20%
year 1; 15% loss
year 2-5; 1% loss total 20%
now that i have not seen any real loss yet. i expect when it starts it will be 10-15% that everyone else is seeing before it levels off. for those few who are seeing more. that might be temporary due to the heat.
I think the mechanisms for heat and cold are different. Whenever Thermodynamics is involved,
things are irreversible.
Understand that the higher/lower power/cap relationship between warm and cold is due to the normal battery chemistry going faster/slower at higher/lower temps. That is the normal function
of the battery. These changes take place on a rather fast timescale (i.e. however long it takes the battery pack to reach a given temperature, a few hours maybe).
Degradation is a totally different animal, that is the chemical process that destroys, if my understanding is correct, the electrodes of the battery. I takes place on a timescale of several years ( or so we hope) AND it is, unlike the normal battery operation, NON-reversible.
So hot temps speed this decay up, low temps slow it down, but ill goes in just one direction.
Put a rotten steak in the freezer and it wont become fresh and tasty again.
It might be however that there is an artificial intervention involved in the process, TickTocks cap vs temperature data indicate an almost linear relationship between temperature and capacity, but opposite to what you would expect from chemistry. So maybe the BMS is doing something...?