Are you confusing IR with **unacceptable** high self-discharge when you say . . . "So 7mV range" ?KiefRichards said:
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Being the datasheet says the shipping voltage is 3.45V i'd be a little perplexed why the voltages are between 3.542V and 3.549V. To me that would border on being a red flag as to who may have had their fingers on those supposedly "new" P42A cells before you received them. Especially if the original shipping voltage of the 210 cells from the manufacture was truly 3.45v per cell.KiefRichards said:
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Are you confusing IR with **unacceptable** high self-discharge when you say . . . "So 7mV range" ?IR and high self-discharge are possibly related, but each requires different testing methods. Unless you have some very expensive equipment for testing all 210 cells it would be very time consuming and labor intensive. A task no one would welcome.Never test a P42A cell for high self-discharge unless it's voltage is at least 3.75v or preferrably charged to 4.00v followed by several days of relaxing decay stablilizing ... then a 10-day rest before testing for unacceptable self-discharge (e.g. -7mV) as explained in the following procedure ... https://endless-sphere.com/forums/viewtopic.php?f=14&t= . . . was that by chance why you mentioned . . . "So 7mV range" ?Being that no one that i'm aware of has mentioned that P42A is prone to high self-discharge don't be overly concerned about testing your P42A cells for high self-discharge. That said it's not a bad idea to test a sampling of a few. Maybe the ones having the lowest voltage (e.g. 3.542v). It's never wasted time to take on a new learning experience if you have the time.Before spot-welding all 200 cells (or 180 or 160) the voltages should be between 3.550v and 3.540v (and arranged appropriately).High self-discharge isn't so much of a problem with a pack that's c/d cycled every few days. Because i don't use my Vruzend 10S3P 30Q experimental pack 4 months out of the year (winter), i have the time to disassemble and replace any 30Q cells suffering from unacceptable high self-discharge. Then during 8 months out of the year i usually cycle the pack every other day, if not every day. So even if there were any cells suffering from unacceptable high self-discharge it wouldn't be a noticeable problem in just 2-3 days.Being the datasheet says the shipping voltage is 3.45V i'd be a little perplexed why the voltages are between 3.542V and 3.549V. To me that would border on being a red flag as to who may have had their fingers on those supposedly "new" P42A cells before you received them. Especially if the original shipping voltage of the 210 cells from the manufacture was truly 3.45v per cell.If you got a good deal price wise on all 210 cells they may not be as "new" as you were led to believe. That's why it's not only important to test IR, but also a sampling of the lowest voltage cells for the possibility of unacceptable self-discharge. In the end it may be best to build a 20S9P or 20S8P pack instead of a 20S10P pack. In the long run doing so could save you a fair amount of frustration; espcially if your DIY build is spot-welded and a pain to later partially disassemble to replace one or more bad cells.
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Lithium-ion batteries are the most common battery in consumer electronics. They are used in everything from cellphones to power tools to electric cars and more. However, they have well defined characteristics that cause them to wear out, and understanding these characteristics can help you to double the life of your batteries ' or more. This is especially useful for products that do not have replaceable batteries.
Battery wear is loss of capacity and/or increased internal resistance. The latter is not a well-known concept, but over time the battery is able to put out less amperage as the battery ages, and eventually the battery is unable to generate power quickly enough to operate the appliance at all even though the battery is not empty.
The standard disclaimers apply, all advice is for informational purposes only, CleanTechnica is not responsible for any damages caused by inaccurate information or following any advice provided. Also, new technology may change the characteristics spoken about, making them less or more relevant in the future or even rendering them obsolete.
These articles explain each facet in detail and are worth reviewing if you're interested in understanding the logic behind the following recommendations.
Try to buy batteries when you need them, because lithium ion ages from the moment it leaves the assembly line. However, by following the recommendations below you can get a longer lifetime from the batteries you own. If possible, look for the date stamp on any battery powered item you intend to buy and try get the newest one. Often you will find it on there, either on the outside of the package or on the item itself.
One cycle is fully charging the battery and then fully draining it. Lithium-ion batteries are often rated to last from 300-15,000 full cycles. However, often you don't know which brand/model of battery is in the item you buy.
Partial cycles will give you many more cycles before the battery wears out, so when possible do partial discharges and then recharge. Don't intentionally drain a battery before recharging for lithium-ion batteries.
For some equipment this is not realistic, in electric lawnmowers and other outdoor tools for example, but the manufacturer will hopefully have selected a battery chemistry designed for this use case.
Try to keep your batteries cool whenever possible. Don't store a cellphone or other portable lithium battery in a car on a hot day, and keep them cool when not in use (bring your portable tool batteries inside instead of leaving them in an unconditioned shed/garage). Park an electric vehicle in the shade or a reasonable temperature garage when possible. Many EVs have active cooling of batteries so that will take care of this for you, although you still save battery power by parking in the shade or a conditioned garage.
Also, your pocket is about 30ºC, so store your cellphone on a desk and out of direct sunlight if you're in the office or at home when practical.
Charge your battery at a slow rate when possible. For a cellphone, use a charger that is rated for about 1/4 of the battery capacity if you can. Avoid quick charging except for rare instances when you absolutely need the most juice as quickly as possible. Charging at 1/2 its capacity per hour is acceptable but chargers that can charge a in under 1.5 hours from empty can be very hard on the battery.
For power tools, try to get a slow charger instead of the quick chargers many of them come with. This is not always possible, but often is.
Don't leave any device connected to the charger once charging is complete. In fact, you should aim to charge to a maximum of 80% (more on that below).
Try not to abuse your battery by pulling as much power as quickly from it as possible. For an EV, flooring the acceleration pedal on a regular basis is not good for the battery. Similarly, power hungry games can drain cellphone batteries quite quickly as well. If your gets hot from high power use (and not the sun or high room temperature), it is an indication that you are punishing the battery.
Sometimes taking it easy on batteries is not always possible because some products, such as lithium-ion powered tools, are hard on the battery by design (drills, lawnmower, snowblowers, etc.). In these cases, manufacturers will typically use batteries designed for high drain rates (but have lower capacity), but anything you can do to be gentle on even these batteries will pay dividends in longer life. For power banks, try to use the power at a moderate rate. USB models can be tricky to limit your current draw rate as a or tablet will draw what it wants up to the bank limit, but for non-USB items you can often try to limit how quickly it's drawing power.
Also you can 'hack' this issue by buying and using a larger capacity battery if your device can handle it. For the same power draw, a larger capacity battery will have a lower percent drain per hour. This also reduces cycle count.
For items you don't use daily, check on your batteries from time to time in case they are draining themselves when not in use. For EVs and cellphones, this is not a noticeable problem, but for power tools and power banks it is a good idea to check on the battery every few months (or weeks if it drains itself quickly) and top it up to 50%-ish for storage.
Unlike most other battery types (especially lead acid), lithium-ion batteries do not like being stored at high charge levels. Charging and then storing them above 80% hastens capacity loss. So charge the battery to 80% or a bit less if that will get you through the day/week. Most EVs have the ability to select a percentage to charge up to in the software.
Charging above 80% is not a big problem if you intend to draw it down quickly and need the full capacity. Of course, try not to do this regularly if you don't have to. Avoid overnight charging of your unless it has a smart charging feature, such as some Apple phones. For Android phones, use Accubattery software or similar, which will beep at 80% charge as a reminder to unplug the cord. Charge to full in the morning if needed to get through the day.
Similarly, for your EV if you have a long driving day planned, setting the software to charge to full by morning (not storing the vehicle overnight at full) and driving until you are below 80% rather quickly will not cause much extra wear to your batteries.
In general, it's the storage time above 75-80% that causes most of the extra high charge wear.
For storing batteries long term, charge them to about 50% and check on them every now and then.
For more information, please visit pouch lithium battery assembly machine.
According to many sources, lithium-ion doesn't like being fully discharged. So try to avoid draining your batteries below about 25% when possible. If unavoidable, then charge it back up to above 25% as soon as possible so the time spent near empty is minimized.
End of life for a lithium-ion battery typically occurs when the battery can no longer perform the function the user requires of it. Commercially, when a battery (pack) has reached 80% of its design capacity it is considered EOL, but for end users, it's typically looked at as when the device (or battery pack) becomes unusable.
When your battery starts acting funny, it can mean it's ready to be retired. Some Apple phones have the ability to calculate capacity remaining (it is buried in the settings) and Accubattery for Android can do the same thing if installed and used for at least a week.
These are some of the strange quirks you may run into that can occur with worn out lithium-ion batteries:
Be sure to recycle all batteries at the end of their life as they contain valuable materials that can be recycled into new batteries.
Charging algorithm = Battery is charged at Constant Current, then near full charge (typically over 80%) the charger switches to Constant Voltage. The charging rate slows until the battery reaches 100% charge. Many EVs modify this algorithm.
C = Capacity of the battery
Series = Multiple batteries linked in a chain to increase the total voltage of the pack.
Parallel = Multiple batteries linked side by side to increase amperage instead of voltage.
(x)S(x)P configuration = explains how multiple batteries are linked. 4S2P for example means 8 cells, four in Series and two Parallel rows
Volts (V) = Electric potential. Power outlets are measured in volts.
Amps (A)= Number of Coulombs of electrons carrying those volts.
Watts (W)= Volts x Amps. Energy/Power usage is often measured in watts. A kilowatt is watts. kWh is Kilowatts per hour.
Energy is measured in Joules and is convertible to Watts/second if you have a time component.
Power = Energy over Time. Typically measured in Watts. One Joule per second is 1 watt. The same number of Joules or Watts in half the time is twice the power.
Nominal voltage = Voltage used to calculate Watts of a battery.
Battery capacity = How many Ah of power the battery can output (when new).
Load = Device that uses the power from the battery.
Internal resistance of a battery affects its Power output. Increased internal resistance is the reduction in rate of Power output the battery can deliver. Energy output is affected somewhat by increased internal resistance.
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