J'aurais plutôt dit 30-40% pour le stockage (40% = ~3,7V). Une tension élevée favorise une oxydation irréversible de la batterie (en charge ou en stockage). Et le froid ralentit (le chaud accélère) les réactions chimiques, y compris d'oxydation, donc c'est logique pour le frigo (le froid ralentit aussi la décharge => baisse du courant max).
Le pire mesuré étant 40% de perte définitive de capacité au bout de 3 mois de stockage lorsque la batterie est chargée à 100% (=4,2V) et stockée à 60°C (ex: véhicule dans un pays chaud...).
Définition usuelle d'un cycle de décharge : "normalement" c'est jusqu'à 0%, l'industrie utilise plutôt jusqu'à 20%, et d'autres ont des compteurs plus exotiques...
http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
Temperature
40% charge
100% charge
Table 3: Estimated recoverable capacity when storing Li-ion for one year at various temperatures.
Elevated temperature hastens permanent capacity loss. Not all Li-ion systems behave the same.
0°C
25°C
40°C
60°C
98%
96%
85%
75%
94%
80%
65%
60%
(after 3 months)
Depth of discharge
Discharge cycles
Table 2: Cycle life as a function of
depth of discharge. (nombre de cycle jusqu'à Une capacité max=70% capacite initiale)
A partial discharge reduces stress and prolongs battery life. Elevated temperature and high currents also affect cycle life.
100% DoD
50% DoD
25% DoD
10% DoD
300 – 500
1,200 – 1,500
2,000 – 2,500
3,750 – 4,700
Charge level (V/cell)
Discharge cycles
Capacity at full charge
Table 4: Discharge cycles and capacity as a function of charge voltage limit.
Every 0.10V drop below 4.20V/cell doubles the cycle but holds less capacity. Raising the voltage above 4.20V/cell would shorten the life. Guideline: Every 70mV drop in charge voltage lowers the usable capacity by 10%.
[4.30]
4.20
4.10
4.00
3.92
[150 – 250]
300 – 500
600 – 1,000
1,200 – 2,000
2,400 – 4,000
~[114%]
100%
~86%
~72%
~58%
What Constitutes a Discharge Cycle?
A discharge/charge cycle is commonly understood as the full discharge of a charged battery with subsequent recharge, but this is not always the case. Batteries are seldom fully discharged, and manufacturers often use the 80 percent depth-of-discharge (DoD) formula to rate a battery. This means that only 80 percent of the available energy is delivered and 20 percent remains in reserve. Cycling a battery at less than full discharge increases service life, and manufacturers argue that this is closer to a field representation than a full cycle because batteries are commonly recharged with some spare capacity left. There is no standard definition as to what constitutes a discharge cycle. Some cycle counters add a full count when a battery is charged. A smart battery may require a 15 percent discharge after charge to qualify for a discharge cycle; anything less is not counted as a cycle. A battery in a satellite has a typical DoD of 30–40 percent before the batteries are recharged during the satellite day. http://batteryuniversity.com/learn/article/discharge_methods