from Battery University about Lipo (also Li-ION) http://batteryuniversity.com/
Similar to a mechanical device that wears out faster with heavy use, so also does the depth of discharge (DoD) determine the cycle count. The shorter the discharge (low DoD), the longer the battery will last. If at all possible, avoid full discharges and charge the battery more often between uses. Partial discharge on Li-ion is fine.
In LiPO There is no memory and the battery does not need periodic full discharge cycles to prolong life
Table 2 compares the number of discharge/charge cycles Li-ion can deliver at various DoD levels before the battery capacity drops to 70 percent. All other variables such as charge voltage, temperature and load currents are set to average default setting. Depth of discharge | Discharge cycles | Table 2: Cycle life as a function of
depth of discharge 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 |
Lithium-ion suffers from stress when exposed to heat, so does keeping a cell at a high charge voltage. A battery dwelling above 30°C (86°F) is considered elevated temperature and for most Li-ion, a voltage above 4.10V/cell is deemed as high voltage. Exposing the battery to high temperature and dwelling in a full state-of-charge for an extended time can be more stressful than cycling. Table 3 demonstrates capacity loss as a function of temperature and SoC. 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) |
Most Li-ions charge to 4.20V/cell and every reduction in peak charge voltage of 0.10V/cell is said to double cycle life. For example, a lithium-ion cell charged to 4.20V/cell typically delivers 300–500 cycles. If charged to only 4.10V/cell, the life can be prolonged to 600–1,000 cycles; 4.00V/cell should deliver 1,200–2,000 and 3.90V/cell 2,400–4,000 cycles.
In terms of longevity, the optimal charge voltage is 3.92V/cell. Battery experts believe that this threshold eliminates all voltage-related stresses; going lower may not gain further benefits but induce other symptoms. (See BU-808b: What causes Li-ion to die?) Table 4 summarizes the capacity as function of charge levels. All values are estimated. 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 reduction in charge voltage keeps 10% of usable capacity vacant | [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% |
Most chargers for mobile phones, laptops, tablets and digital cameras bring the Li-ion battery to 4.20V/cell. This allows maximum capacity, because the consumer wants nothing less than optimal runtime. Industry, on the other hand, is more concerned about longevity and may choose lower voltage thresholds. Satellites and electric vehicles are examples where the importance of longevity surpasses harvesting maximum capacity.
For safety reasons, many lithium-ion cannot exceed 4.20V/cell. (The exception is the high energy-dense NMC that charges to 4.30V/cell.) While a higher voltage boosts capacity, exceeding the voltage shortens service life and compromises safety. Figure 5 demonstrates cycle count as a function of charge voltage. At 4.35V, the cycle count of a regular Li-ion is cut in half. |
Figure 5: Effects on cycle life at elevated charge voltages Higher charge voltages boost capacity but lowers cycle life and compromises safety. Source: Choi et al. (2002) |
Besides selecting the best-suited voltage thresholds for a given application, a regular Li-ion should not remain at the high-voltage ceiling of 4.20V/cell for an extended time. When fully charged, remove the battery and allow to voltage to revert to a more natural level. This is like relaxing the muscles after strenuous exercise. Although a properly functioning Li-ion charger will terminate charge when the battery is full, some chargers apply a topping charge if the battery terminal voltage drops to a given level
LONGEVITY ISSUES:
The Dalhousie University in Halifax under Professor Jeff Dahn studied the longevity of L-ion by coulombic efficiency (CE). CE is a method that defines the efficiency with which electrons are transferred in an electrochemical system.
During charge, lithium gravitates to the graphite anode (negative electrode) and the voltage potential changes. Removing the lithium again during discharge does not reset the battery fully. A film consisting of lithium atoms forms on the surface of the anode called solid electrolyte interface (SEI). Composed of lithium oxide and lithium carbonate, the SEI layer grows as the battery cycles. The film gets thicker and eventually forms a barrier that obstructs interaction with graphite. (See BU-701 How to Prime Batteries)
The cathode (positive electrode) develops a similar restrictive layer known as electrolyte oxidation. Dr. Dahn stresses that a voltage above 4.10V/cell at elevated temperature causes this, a demise that can be more harmful than cycling. The longer the battery stays in the high voltage, the faster the degradation occurs. The build-up can result in a sudden capacity loss that is difficult to predict by cycling alone. This phenomenon had been known for some years and measuring the coulombic efficiency can verify these effects in a more scientific and systematic manner.
Discussion:
So it seems that DJI is giving wrong info about deep discharge.. it actually may damage cells. I think tyou may want to do it once to caliberate the battery BUT not needed each 10 cycles as the new firmware makes you do!!Field use revealed that the combination of heat and high voltage can cause more stress to Li-ion than harsh cycling.
Lithium-ion is a very clean system that does not need additional cycling once it leaves the factory, nor does it require the level of maintenance that nickel-based batteries do. Additional formatting makes little difference because the maximum capacity is available right from the beginning, (the exception may be a small capacity gain after a long storage). Nor does a full discharge improve the capacity once the battery has faded. A low capacity signals the end of life. A discharge/charge may only be beneficial to calibrate a “digital” battery; it does nothing to improve the “chemical battery.” (See BU-601: Inner Working of a Smart Battery) Instructions recommending charging a new battery for eight hours do not cause harm but this is “old school,” a left-over from the old nickel battery days.
Arun Mehta
| 
lvl.3
lvl.4
New
lvl.2
Might dial in a tad of expo on a couple of axis and dial down the braking a stop. I recon that thing pulls 10g from max speed to letting go of the sticks.