http://web.mit.edu/evt/summary_battery_specifications.pdf
A battery is a device that converts chemical energy into electrical energy and vice versa.
A battery's capacity is rated in amp-hours (Ah). For example, a battery with 100 Amp-hours can provide 100 amps of current for one hour.
The capacity can drop over time.
SOC is a measurement of ( current capacity / total capacity ). SOC is generally calculated using current integration to determine the change in battery capacity over time.
Terminal Voltage (V) – The voltage between the battery terminals with load applied. Terminal voltage varies with SOC and discharge/charge current. Rubber band effect.
Open-circuit voltage (V) – The voltage between the battery terminals with no load applied - when the battery is in a relaxed state. This is the true voltage.
Nominal Voltage Cut-off Voltage
Nominal Capacity - The coulometric capacity, the total Amp-hours available when the battery is discharged at a certain discharge current (specified as a C-rate) from 100 percent state-of-charge to the cut-off voltage. Capacity is calculated by multiplying the discharge current (in Amps) by the discharge time (in hours)
Nominal Energy - The “energy capacity” of the battery, the total Watt-hours available when the battery is discharged at a certain discharge current (specified as a C-rate) from 100 percent state-of-charge to the cut-off voltage. Energy is calculated by multiplying the discharge power (in Watts) by the discharge time (in hours)
C-rate - Discharge current is often expressed as a C-rate in order to normalize against battery capacity, which is often very different between batteries. A C-rate is a measure of the rate at which a battery is discharged relative to its maximum capacity. A 1C rate means that the discharge current will discharge the entire battery in 1 hour. For a battery with a capacity of 100 Amp-hrs, this equates to a discharge current of 100 Amps. AKA - % capacity discharge per hour.
https://www.nature.com/scitable/blog/eyes-on-environment/solving_the_silicon_swelling_problem
Typical batteries consist of a lithium (Li) metal cathode and an anode separated by a liquid electrolyte (solvent) that transfers lithium between the two electrodes. Batteries provide power by discharging lithium from the anode (+) to the cathode (-) via the electrolyte. To date, most lithium-ion batteries use anodes made of graphite, layers of carbon sheets arranged in hexagonal patterns. The wide space between these layers provides the perfect location to store lithium atoms moving into and out of the anode as the battery charges and discharges. The maximum amount of lithium that can be stored in the anode determines the battery's capacity.
http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries
constant current (~1 hour), then saturation charge phase (can take a few hours) (Also called constant voltage phase). voltage threshold charge characteristics
Speeding up the current - using a higher current - will only speed up the first phase of charging. The second phase where of sustaining charge will take longer.
http://batteryuniversity.com/learn/article/how_to_store_batteries
The recommended storage temperature for most batteries is 15°C (59°F); the extreme allowable temperature is –40°C to 50°C. lithium-based chemistries should be stored at around a 40 percent state-of-charge (SoC). To get the correct reading after a charge or discharge, rest the battery for 90 minutes before taking the reading.
Storage induces two forms of losses:
- Self-discharge that can be refilled with charging before use,
- Non-recoverable losses that permanently lower the capacity.
Batteries should be stored at 40% charge. Don't leave it fully charged! at 0C, there is the least capacity lost for any storage level. 25C is the second most optimal.
Lithium-ion must be stored in a charged state, ideally at 40 percent. This prevents the battery from dropping below 2.50V/cell, triggering sleep mode
http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
The lithium-ion battery works on ion movement between the positive and negative electrodes. In theory such a mechanism should work forever, but cycling, elevated temperature and aging decrease the performance over time.
The performance of a battery is measured in capacity, a leading health indicator.
Li-polymer batteries
Depth of discharge (DoD) determines the cycle count of the battery. The smaller 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.
browning out a system - shorting or burning? or discharging the battery all the way to 0 and making it unrecoverable?
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.
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.
Batteries charging to 85% have a longer life span than enabling full charge (100%). Although longer lasting, a less than full cycle does not fully utilize a battery.
75–65% SoC offers longest cycle life
http://batteryuniversity.com/learn/archive/pouch_cell_small_but_not_trouble_free
The pouch cell makes the most efficient use of space
Small mentions of pouch swelling, but not how to prevent it. Swelling as a result of gas generation during charge and discharge is a concern.
http://www.epectec.com/batteries/prismatic-pouch-packs.html
prismatic (Packaged in welded aluminum housings) or pouch cell (soft pack) vs cylindrical cells
Li-Ion technology has higher voltage output per cell than many other systems. Therefore, fewer cells are needed for a given battery voltage.
The prismatic cell requires a slightly thicker wall size to compensate for the decreased mechanical stability from the cylindrical design,
The prismatic cell improves space utilization compared to cylindrical batteries.
To prevent swelling, the manufacturer adds excess film to create a “gas bag” outside the cell. During the first charge, gases escape into the gasbag, which is then cut off and the pack resealed as part of the finishing process. Expect some swelling on subsequent charges; 8 to 10 percent over 500 cycles is normal. Provision must be made in the battery compartment to allow for expansion. It is best not to stack pouch cells but to lay them flat side by side. Prevent sharp edges that could stress the pouch cell as they expand.
http://batteryuniversity.com/learn/article/the_li_polymer_battery_substance_or_hype
With gelled electrolyte added, what is the difference between a normal Li ion and Li ion polymer? As far as the user is concerned, lithium polymer is essentially the same as lithium-ion. Both systems use identical cathode and anode material and contain a similar amount of electrolyte.
https://en.wikipedia.org/wiki/Lithium_polymer_battery
"lithium-ion polymer battery" LiPo
Uses a polymer electrolyte instead of a liquid one. High conductivity semisolid (gel) polymers form this electrolyte. These batteries provide a higher specific energy than other lithium-battery types and are being used in applications, where weight is a critical feature.
A typical cell has four main components: positive electrode, negative electrode, separator and electrolyte.
They have low-self discharge rate, which is about 5% per month.
All Li-ion cells expand at:
- High levels of state of charge (SOC) or over-charge
- Due to slight vaporisation of the electrolyte.
This may result in delamination, and thus bad contact of the internal layers of the cell, which in turn brings diminished reliability and overall cycle life of the cell.
http://learningrc.com/puffed-lipos/
Excess swelling is caused by overcharging and overheating.
Your battery will generate gas through a process called electrolyte decomposition. The electrolyte decomposition occurs even faster if you overdischarge a battery or overheat a battery.
Simply put, a battery is made of three things: the anode, the cathode and the electrolyte. The cathode and the anode are the positive and negative terminals on your battery.
The electrolyte is a chemical inside the battery that allows charged ions to flow from the anode to the cathode during discharge (and the other way during charging).
Electrolyte decomposition is what happens when that electrolyte chemically breaks down. So in a lipo battery, as the electrolyte breaks down you end up with lithium and oxygen. This forms lithium oxide on the anode and cathode (depending whether you are charging or discharging).
But what you also end up with is excess oxygen that doesn’t adhere to the anode or cathode. This excess oxygen is part of what causes a battery swell.
https://superuser.com/questions/805161/enable-lenovos-conservation-mode-on-boot
"Plugged-in not charging" "conservation mode", which keeps the battery charged in the 40-65%
- https://en.wikipedia.org/wiki/File:Expanded_lithium-ion_polymer_battery_from_an_Apple_iPhone_3GS.jpg
- http://www.epectec.com/images/swelling-pouch-cell.jpg
- RC LIPO BATTERY GUIDE: EXPLANATION, SAFETY, AND CARE
- The Swelling Machanism of Lithium-Ion Batteries at High Temperatures
- This is a chemical explination of what causes Li-ion batteries to swell.
- https://www.electrochem.org/dl/ma/203/pdfs/0110.pdf
- Insight into the gassing problem of Li-ion battery
- BU-301a: Types of Battery Cells
- Goes into the different form factors
- http://batteryuniversity.com/learn/article/types_of_battery_cells
- State of Charge as a factor of battery failures
- Lower state of charge makes battery safer when under stress or shorted.
- http://www.prba.org/wp-content/uploads/Exponent_Report_for_NFPA_-_20111.pdf