I see the same question being asked by many newcomers here so I would like to shed some BASIC info on batteries used in esk8, notation, configuration, ratings, etc.

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Battery Notation

Common battery notation you keep seeing or will see is a (XX)s(YY)p battery with (ZZ) cells:

• XX is the number of cells you have in series ( s ) type connection.

• YY is the number of cells you have in parallel ( p ) type connection.

• ZZ is the actual battery cell type used. At the time this article was written, Samsung 30q was by far the most common here. You will also see , , etc mentioned a lot. That is just the physical dimension of the battery cell, nothing to do with chemistry. An is a battery 18mm wide by 65.0 mm long. Panasonic, Sony, LG, etc all make cells. They also make other size cells like the . Can you guess what size that is?

Battery Configuration

Series

When you add cells in series, it adds to the total voltage available to your system.

ex. 30Q cells are 4.2V fully charged,

Ie. 10s is 42V, 12s is 50.4V, 100s is 420V etc.

Parallel

When you add them in parallel, it keeps the voltage the same but adds to the capacity (measured in Ah or more commony mAh).

30Q cells are 3 Ah each (or mAh if you prefer).

Ie. 4p is 12 Ah ( mAh), 10p is 30 Ah, etc.

Very very basically, increasing series adds speed, increasing parallel adds range.
This is assuming you keep all other parts/conditions the same.

Battery Chemistry / Cell Type

If you use the esk8 calculator to design your build on paper before going shopping (highly recommended), you’ll notice there are a number of options in the Cell Type drop-down:

• Lithium-Ion Polymer (Li-polymer / LiPo) pouch packs
• Lithium-Ion (Li-Ion) cylinder cells
• Lithium Iron Phosphate (LiFePo4)
• Lithium Titanate (Li2TiO3 / Li4Ti5O12 / LTO)
• Lead Acid
• Nickel Metal Hydride (Ni-MH)

In 99% of cases, the question to answer is which lithium based battery is best for your use: LiPo or Li-Ion (sometimes LiFePo)?

Some of the following information may be a bit in depth, but beginners will understand more as they read more. Hopefully this is a good reference that can be improved by the community and updated over time. Battery technology develops extremely rapidly, and some of this information will likely be out of date in only a few years.

Common Cell/Pouch Type Info

LiPo

LiPo (typically LCO chemistry, 3.7V nom, 4.2 - 3.6v safe range, polymer gel electrolyte)

General Characteristics:

Cycle_Life: Poor (50-300 charge cycles)
Energy_Density (Specific Energy): Good (100–200 Wh/kg) - Heavier for a given capacity than li-ion / roughly 2x the weight for the same range
Discharge_Rate: Excellent - Highest discharge rates / C rate (“punchy”). Can get much higher discharge on smaller packs if not concerned about range. (10-25C actual / 200A+)
Charge_Rate: Average (1C typical, 3C maximum)
Voltage_Curve: Good - Flatter curve / minimal voltage sag / maintain a higher voltage under load for longer
Cost: Average. Easy to purchase, widely available
Quality: Average - more prone to swings in manufacturing quality, dimensions, and weight
Safety: Poor - Most sensitive to piercing / blunt damage / thermal runaway. Requires hard case for safety. Easily damaged by discharging too far (will unbalance rapidly below 3.6V.
Operating_Temperature: Average, 5 to 50°C charge (damage will occur if charging at over 60°C)
Aging: Poor- easily damaged if left above recommended storage charge for '3+ months
Packaging: pouch packs come in compact ‘bricks’ of varying sizes, encased in a semi-flexible shell. No standard size exists. Easy to replace / swap / carry extra backups, but added complexity of multiple battery packs.
Cell_Balancing: Requires a BMS or balance charger to eliminate state of charge (SOC) mismatch. 
Note: Inaccurate manufacturer C rating is very common (typically around 2-3x exaggerated)
Examples: Gens Tattu, Turnigy Nano-Tech, Turnigy Graphene, Venom, MaxAmps

Read the more detailed lipo thread here: thinking about going lipo
Read the Tattu lipo thread here: Does anyone have experience with Tattu lipo batteries?

Lipos are safe if you maintain them well. If not, they can puff and cause fires. A lithium ion (cylinder) battery pack like discussed below can still burst into flames if you wire it wrong or don’t protect it but are generally safer and easier for beginners. They can give slightly more voltage (power) but also sag faster.

Li-Ion

Li-Ion (typically NMC/NCA chemistry, 3.6V nom, 4.2V - 3.2V safe range, liquid electrolyte)

General Characteristics:

Cycle_Life: Good (- charge cycles)
Energy_Density (Specific Energy): Excellent (160–260 Wh/kg) lighter for a given capacity 
Discharge_Rate: Good (250-430 W/kg) - CDR largely depends on cell and manufacturer (15-35A continuous typical)
Charge_Rate: Average (1C typical, 4C maximum)
Voltage_Curve: Average - Depending on cell, can have significant voltage sag in the last half of the discharge (voltage curve)
Cost: High - significant upfront cost includes individual cells plus the materials and labor to build a finished battery pack with BMS electronics, although individual cell prices have steadily decreased over time.
Quality: Excellent - Extremely tight manufacturing tolerances by large global brands ensure high quality cells. Tend to be higher quality packs than LiPo when assembled by a quality builder
Safety: Average - sensitive to physical damage and short circuiting. Requires hard case for safety.
Operating_Temperature: Good, 0 to 60°C charge, -40 to 60°C discharge
Aging: 0.35% - 2.5% / month. Good - better at sitting for long periods of time unused.
Packaging: cells come in cylindrical steel canisters of precise dimensions, with overpressure vents (most common:  = 18mm dia x 65mm L,  = 21mm dia x 70mm L)
Cell_Balancing: Requires a BMS to keep cells balanced
Note: Tend to be over the limit for air flight (99 Whr), aka cannot travel with an assembled pack.
Examples: Molicel P26A and P42A, Sony Murata VTC5D, VTC5A, and VTC6, Samsung 30Q, 30T, and 40T, LG HG2 and HG6, Sanyo NCRC and NCRA

Example discharge curve:

Read the P42A discussion thread here: Molicel P42A cell discussion LiFePo4

LiFePo4 (3.2V nom, 3.65V - 2.5V range)

General Characteristics:

Cycle_Life: Excellent (- charge cycles)
Energy_Density (Specific Energy): Poor (90-130 Wh/Kg) / poor range/weight
Discharge_Rate: Excellent - 25C / 30A+ continuous
Charge_Rate: Excellent (4C+) fast charge is proven safe.
Voltage_Curve: Excellent (flat) - provides the same voltage across almost the entirety of discharge
Cost: Low
Quality: Excellent - Extremely tight manufacturing tolerances by large global brands ensure high quality cells. Tend to be higher quality packs than LiPo when assembled by a quality builder
Safety: Excellent, stable chemistry - the cathode material will not burn and is not prone to thermal runaway (fire). One of the safest chemistries.
Operating_Temperature: Good, 0 to 55°C charge, -30 to 55°C discharge
Aging: ≤ 6% self-discharge. More tolerant to being left at full charge voltage. Higher self-discharge rate than other chemistries. 10 year shelf life.
Packaging: cells come in all forms including cylinders, pouches, and prismatic packs.
Cell_Balancing: Requires a BMS to keep cells balanced
Examples: A123 ANRM1B

Read the A123 thread here: A123 LiFePO4 Cells - the iron man’s battery

LTO

LTO (2.4V nom, 2.8V - 1.5V range)

General Characteristics:

Cycle_Life: Excellent (- charge cycles)
Energy_Density (Specific Energy): Bad (60-110 Wh/kg)
Discharge_Rate: Excellent (5C typical, 30C+ maximum)
Charge_Rate: Excellent (1C typical, 20C+ maximum)
Voltage_Curve: Good
Cost: High?
Quality: 
Safety: Excellent - One of the safest chemistries.
Operating_Temperature: Excellent, -10 to 40°C charge, -30 to 75°C discharge
Aging: ≤ 5% self-discharge / month.. >10 years shelf life.
Packaging:
Cell_Balancing: 
Examples: 

Voltage Discharge curve:

Lead Acid (SLA)

Lead Acid (2.0V nom, 2.3V - 1.8V range)

General Characteristics:

Cycle_Life: Poor (200-350 charge cycles)
Energy_Density (Specific Energy): The Worst (30-40 Wh/kg)
Discharge_Rate: Good (180 W/kg), 1C - 3C 
Charge_Rate: Bad (≤0.2C)
Voltage_Curve: 
Cost: Low
Quality: High, simple to manufacture
Safety: Good. Although environmentally unfriendly
Operating_Temperature:  -40 - 50°C. Good low and high temp performance.
Aging: 3-20% / month. Slight memory effect.
Packaging:
Cell_Balancing: 
Examples: automotive starter batteries

Ni-MH

Ni-MH (1.2V nom, 1.4V - 1.0V range)

General Characteristics:

Cycle_Life: Poor (~500 charge cycles)
Energy_Density (Specific Energy): Bad (60-120 Wh/kg)
Discharge_Rate:
Charge_Rate: Excellent - only battery that can be ultra-fast charged with little stress
Voltage_Curve: Excellent  - 'low internal resistance allows cells to deliver a nearly constant voltage until they are almost completely discharged.
Cost: Low
Quality: 
Safety: Good. Requires complex charge algorithm, sensitive to overcharge.
Operating_Temperature: -20 - 50 °C. 
Aging: '1-4% self-discharge. 
Packaging -
Cell_Balancing -
Note - Similar to NiCd, but less toxic. Constitute less than 3% of the battery market.
Examples: Eneloop rechargeable NiMH

Battery Cell Ratings

Yes, voltage and capacity (those mAh numbers) matter very much. Remember the examples above with series vs parallel?

25r cells are mAh cells and sag faster than 30q
30q cells are mAh cells - comparative example
40t cells are mAh cells and sags less than 30q

25r is what many prebuilts used to use and were fine. They just won’t carry you very long. Most newcomers I saw when I first joined were upgrading their prebuilt batteries with 30q packs. Currently (as of 12/30/21), the Molicel P42a is the cell of choice for power discharge, high charge rate, and all around solid performance.

@Battery_Mooch is a gentleman and a scholar and also conducts professional cell discharge tests that analyze cell performance under various conditions. If you ever want no BS, solid rating values for cells, search “Mooch insert cell type here” and you should find his results. Mooch, if you have a preferred link you’d like me to drop, Lmk and I’ll fix or adjust the wiki yourself

[Mooch’s response] Thank you @Venom for your kind words!
All my test results and tables can be found here: https://www.e-cigarette-forum.com/blogs/mooch./
While I post some content here I also post to my Mooch Facebook page.

You can not mix cell types. Also don’t mix cells of different age (how many times they’ve been used/charged - called cycles). I don’t want to hear any of that “well technically you can if…” talk. This is a battery basics thread!

Each cell also has a listed amp draw rating. The aforementioned Mooch finds reliable discharge and capacity ratings so that we don’t kill our packs faster than we should.

Example: 30q cells are rated at 15A discharge by Samsung, 20A by Mooch (as long as they don’t overheat!)

Your battery’s total available amp discharge is your cell type’s individual amp draw times your number of parallel groups.

I.e.

A 10s5p of 30q cells will have a max battery amp draw of 100A (20A per cell * 5 parallel groups)

Notice a 12s5p will still have the same max battery amp limit. This is where people will use larger cells to have higher available battery discharges without as many p groups. But… the cells are also physically bigger so factor that in as well.

ESC - After the Battery Upgrade

Your motors are dumb devices. They will happily take whatever your battery sends at them even if it melts them into oblivion. This is where your electronic speed controller (ESC) comes in. It sets the limits of amps (and tons of other things) going to your motors using complex maths I won’t get into. As long as your ESC can handle the voltage rating of your new battery and you stay within its acceptable operating range, you’re good to go. You will find this in the esc specs.

BMS and Charging

It stands for battery management system (BMS). It is wired to your battery and keeps the charge even across all of your parallel groups so your battery doesn’t get unbalanced and have problems.

Charging should be done through the bms to prevent overcharging of individual parallel groups. If the pack is unbalanced after discharging, some of the groups can reach their maximum voltage before others and before the charger would reach its cut off voltage. The bms monitors the individual cell voltages and cuts off charging if any one parallel cell group exceeds its maximum allowable voltage preventing damage and or fires

You can charge your pack at different rates as long as they match your pack’s voltage. The charger will be rated in amps to let you know how quickly it will charge your pack. Might as well charge as quickly as possible right? Eh not so much. Charging too quickly is bad for cells and will shorten their lifespan. Charging slowly is best for your pack but worst for riding your esk8 around aot.

Here is a conservative charge rate formula that isn’t painfully slow either:

[# of parallel groups] * [cell type mAh rating / ]

For more Cylindrical Battery PACK Lineinformation, please contact us. We will provide professional answers.

Additional reading:
Why is Fiberglass Texturized Yarn Better?
5 Things to Know Before Buying 10ft Expandable Container Home

For a 10s5p 30q pack (30q cells rated at mAh):

[5] * [/] = 5A charge rate.

Again, you can certainly charge faster or slower than that, this is just my personal recommendation.

Do not ever let your battery pack drain below recommended levels! For this reason, many bms and escs have a hard voltage cutoff where your board will cut all acceleration when too low (cutoff end). You see this happening most going up hills as this draws more power. Most escs used here take it a step further and implement a soft cutoff where, instead of throwing you on your face at a low voltage level, it will slow your board down gradually going to that point (cutoff start). Almost like you’re wounded and limping home to your charger. This brings up the next question, what is a safe discharged rating?

Battery Cutoff Settings

Read the ongoing thread: ESC Battery cutoff settings - #6 by b264

12S lipo (50.4V charge)
cutoff start 45.24V
cutoff end 44.52V

12S li-ion; super-conservative (50.4V charge)
cutoff start 43.2V
cutoff end 40.8V

12S li-ion; conservative (50.4V charge)
cutoff start 42V
cutoff end 38.4V

12S li-ion; aggressive (50.4V charge)
cutoff start 38.4 - 39.6V
cutoff end 36V

12S li-ion; max-range (50.4V charge)
cutoff start 43.2V
cutoff end 36V

Please keep comments to basic-moderate battery related questions. All advanced battery construction questions should be posted in the battery builders club thread and ONLY AFTER READING THE WHOLE THREAD please.

More general introduction guide here: Wiki for new users [Help Wanted (Example part list, FAQ)]

Welcome to Esk8!

Like I said, rechargeable lithium-ion batteries are everywhere! This is what makes getting these batteries cheap because people tend to toss old electronics that get broken or just stop working, but leave the battery inside. I usually get mine from the thrift store for pennies, or from old toys people give away or get broken and donate for science. The ones to look for are as follows: hand-held devices, cell phones, digital cameras or camcorders, portable DVD or video players, and my personal favorite, laptop batteries. There are different chemistries associated with rechargeable lithium-ion cells as well such as lithium cobalt oxide (ICR-type), lithium iron phosphate or LiFePO4, (you won't encounter these being thrown away often), lithium manganese oxide (IMR), lithium manganese nickle (INR) and lithium nickle manganese cobalt oxide (NCA or hybrid). The MOST common you will find are the ICR-type lithium cobalt oxide. It's the best for energy density and power, but has average to low discharge current and temperature threshold. The maximum discharge current for these is equal or at least double the capacity at most. Plus, they are less stable (read: dangerous) than the other types and need to have some kind of protection circuitry. Now, let's not confuse lithium-ion batteries with lithium-ion polymer batteries or LiPo batteries. In LiPo batteries the electrolyte, anode, and cathode, positive and negative terminals, are housed in polymer pouches. The internal chemistry is similar to lithium-ion cells. Depending on the device, the battery will be different in shape or size, but they are usually rectangular and thin for cell phones or compact devices, or cylindrical like (common in laptop batteries) or common in hump packs for cameras or camcorders.

In case you've ever wondered, the name of the battery contains its dimensions. "" means the battery is 18 mm in diameter and 65 mm long. The "0" is just hanging out. Regardless of the type or size, these may have a single cell, or multiple cells. Multiple cells are either in series or parallel, or a mix of both. Even small batteries can have two small cells inside connected in series or series/parallel. This is due to the fact that some devices have increased voltage needs more than a single cell can provide, or to add capacity. Series connections increase the voltage, and parallel connections increase the capacity of the pack. Unlike NiMH or NiCad batteries, lithium-ion battery packs will have some kind of protection device in them like a battery management system consisting of IC's and MOSFET's or resistors that regulate current, voltage, detect short circuits, reverse polarity, and temperature. Some have an added function of balancing the cells if there are multiple cells. Why do they need this? It's because the chemistry of the lithium cell makes it sensitive to over charging, over- discharging (draining until the voltage gets too low), short circuit, and even over temperature. Any of those can damage the cell, or worse, cause a fire. Multiple cell batteries in series need the balance function that makes sure each individual cell receives the same amount of current and voltage as the other cells. If one cell gets more charge than another one, it can wear out faster or get damaged. The capacity of the pack is also reduced. These types of batteries also require special charging procedures that NiMH or NiCad's don't. More on that later!

Now before we start digging into battery packs, I want to touch on some safety items specific to lithium-ion cells. If you're into RC and have electric vehicles and have experience with LiPo batteries, you can skip this, but if not, it's important to understand that messing with lithium-ion batteries can be hazardous. I learned this the hard way!

Why? Due to their chemistry, a single cell holds a lot of energy. Strap 6 or more together, and you have a lot of stored energy. The safety consideration comes if they are short-circuited, over charged, or under charged, or over discharged, the most common type of lithium battery heats up, swells, and can explode, or cause a fire from getting so hot, which we don't want.

The way to avoid this is to handle and charge them correctly. Most all lithium-ion battery packs or single batteries have some kind of protection circuitry built into them to protect the cell from being overcharged, short circuited, or over discharged. Multi-cell packs have an added feature called a battery management system with a balance function that monitors and distributes charge current and voltage across each cell, making sure each gets charged with the same amount of current and voltage. That said, you must use an appropriate charger, either for single cells or one that supports multiple cells in a pack such as a balance charger. Using any other charger could cause the lithium-ion cells to overcharge and result in a fire.

Extracting cells is pretty straightforward. You need some basic tools, so here are the essential ones:

Flat blade screwdrivers. It's good to have various sizes, but generally 3 mm (1/8") up to 5 mm (or 1/4") are all you need. Avoid thicker blades as they are too big to fit into small spaces.

Spudger (optional). A sturdy metal one, or strong plastic one for separating cases.

Side cutters or flush cutters. For cutting tabs or wires, or cutting the battery case open. Both work, but I like my flush cutters because they get into small spaces better.

Utility knife. Works better than a spudger, but more dangerous! Ask my fingers and hands how I know this 8)

Multimeter. Don't need a Fluke or anything fancy for this. It's just for measuring the cell voltage to see if they are salvageable.

Gloves (optional). I say optional because practical gloves for this task probably won't stop a sharp screwdriver blade or utility knife blade that's slipped out of a joint at high velocity.

Those are all the tools you need!

You have the battery, the tools, and now it's time to dig in. I am taking apart two battery packs in this tutorial. One is a generic 6-cell pack for an HP Pavilion Dv 5 to Dv 6-series laptop and a pack from an ancient ( vintage) digital camera rated at 7.4 volts and mAh. I think it has two cells inside, but we'll find out.

Depending on the type of battery, the basic design is going to be pretty much the same, consisting of a plastic outer casing containing a liner for insulation or cushioning (foam, silastic, tape, or paper), the cell(s), a protection device/board with its internal connections, either wires, tabs, or wires and tabs. By the way, I've noticed little to no difference in construction between generic (like the laptop battery) and genuine OEM (like the camera battery). Sometimes the case is welded or glued, but other times it's just held together with tabs. You will find out quickly which method the manufacturer uses. OEM batteries are usually glued/welded and cheaper ones are glued or clipped in.

I like to start at the corners of the case with the utility knife first. Find the seam between the two case halves. Inset the knife along the edge. Rock it back and forth to get it going in the case. It should sink in, so be careful not to go too deep and cut the cells or short something out. Once you get it going and have opened up a small gap, time to go for the screwdriver. Use the smaller screwdriver to open the gap further by twisting it. Once you get it opened more, go for the bigger screwdriver and repeat. You should start getting large creases in the case. Move the screw driver up the seam of the case, twisting as you go. If you aren't getting anywhere, go back to the knife and repeat the first step. I don't think I need to remind you to be careful here.

If you're stuck, resist the urge to use a hammer or break out your Dremel tool with a cutoff wheel. If you're like me and impatient, then be super-careful! Batteries don't like being cut open. For the record, I've never had to use mine.

Keep working the screwdriver up the seam and separate the case halves. You can use a sturdy spudger here as a wedge to keep the halves spread open while you work the screwdriver. Be patient! It will give up before you! Don't be afraid to be physical with it. Pry the case apart if needed and dig out the goodies inside.

After some finaggling you should have the case fully or mostly separated and can behold the goodies inside! This is the other fun part, figuring out what you've got inside.

My two batteries happen to have cylindrical cells, but I'll include a flat one so you can see the difference.

The laptop pack has some pretty decent Moli Energy (now called E-One) brand ICR-J cells. These are a lesser-known brand that was once located in Canada (now in Taiwan), but are in a variety of devices. I checked the data sheet and they are mAh capacity and rated at mA discharge current maximum, 4.2 volts full charge and 3.75 volts nominal charge, and 3 volts discharged. The other pack contains some mysterious cells that are wrapped in plastic coated paper, but I measured them and they come out as 49 mm long and 18 mm wide. I think they are -size lithium-ion cells. The battery case said mAh for them and 7.4 volts, so there are two cells in series. I would imagine they are good-quality cells since this is an OEM pack, but who knows?

Inside the case we have the same basic features. Both have a battery management board that consists of the protection and balance circuits. The laptop battery adds another important feature, a thermistor for monitoring the temperature of the battery. These are designed for maximum capacity and low drain, so you won't find any heavy-duty components like with some other protection circuits.

Taking a look at the arrangement of the batteries, the laptop battery has 6 cells in a series/parallel arrangement, so 3 cells in series to generate the 11.1 volts, and 2 cells in parallel to double the capacity to mAh. The camera battery has 2 cells in series, so the capacity is the same, but the voltage is doubled.

While it's okay to keep the cells connected, you will want to separate them for charging and analyzing. Lithium cells in battery packs are always connected by spot welded tabs that connect the positive and negative terminals and you need to be careful when cutting them. Use the side cutters or the flush cutters to carefully cut the tabs between the cells and avoid shorting across the terminals. Be careful not to damage or remove the protective wrap on the outside of the cell as you can short on the metal body as well while cutting the tabs. We don't want naked batteries. Use the needle nose pliers to remove the tabs by pulling them off. Be careful. The cut edges of the tabs are razor sharp!

Now you have your batteries, was your hard work worth it? The problem with salvaging batteries is you don't know how well they were cared for or how old they are. Lithium-ion batteries are sensitive to over and under-discharging. Any time they are discharged too deeply, then fully charged, they lose capacity. You can check the age of the battery pack, and measure the voltage (if able), or check for date codes on the circuit board inside. Most of the time, these batteries will be dead, and I mean dead. Lithium-ion cells don't like to be discharged below their over discharge voltage, usually between 2.5 and 2.75 volts at the most. Below that and the cell goes to "sleep" or is so dead it won't take a charge anymore, and if you do manage to get charge in it, the capacity will be so low that it's unusable. If you can measure the battery before you take it apart (like our camera battery with exposed terminals), you are looking for 4.2 to 3 volts for a single cell, so our laptop battery fully charged is 12.6 volts and 9 volts discharged. I measured it after I dissected it and it was a pretty-much-dead 5.6 volts with each cell reading around 1.8 volts.

The camera battery is in much better shape, with the pack showing a fully-charged 7.9 volts and each cell at 3.9 volt, but we don't know how healthy they are, or how much of their capacity has been lost over the years.

If your batteries read under 2 volts, then they are "dead." If they read 0 volts, then they have entered a sort of hibernation state and are probably not worth keeping as even if you revive them, they will have been damaged. Recycle them properly. You can salvage the very low voltage cells, but you need a special charger that can 'revive' dead batteries, or use some techniques that can bring them back to life.

You have your batteries, but they're dead. Now what? All is not lost because you can revive them. If you have a balance charger designed for charging LiPo batteries, chances are it will revive your lithium-ion cells too. Or, if you have a digital multicharger that has 'revive' functionality, that will work too. I am using a Chinese clone of a SkyRC iMax B6 charger, and a Zanflare C4 multicharger. The Zanflare has the ability to revive dead batteries and has an analyzer function, but the iMax doesn't.

To use the Zanflare, just insert the dead batteries and let the charger do the work. Always start at the lowest charge current possible. The Zanflare goes down to 300 mAh, so that's fine. It will take a while, but be patient. Let them fully charge, and take them off the charger. Let them sit overnight or a couple days and see if they've lost their charge. If they have significantly self-discharged, then toss 'em, but if they're still holding the charge then chances are you've revived them, but time will tell as you use them whether you are successful. You can run some test cycles on them to see how much life they've lost as well by doing a charge-discharge cycle or two and check the capacity. You can also measure the internal resistance of the cell if your charger has the cell analyzer function, which the Zanflare does. Take this with a grain of salt because lots of variables effect internal resistance, but generally a number around 230 miliohms is a good figure.

If you don't have a Zanflare or other charger/analyzer with revive function, you can use your LiPo charger. Now as a safety feature, most of these chargers will not charge a cell under that 2.6 to 2.5 volt range, but there's a workaround. Just be careful! Charging a lithium-ion cell like a NiMH will cause bad things to happen! Set the charger to the NiMH mode where you can manually select the charge current. Set the current to something like 200 mA and start charging. Monitor the voltage until it gets above 2.8 and stop the charging process. Set the charger to the LiPo/Li-on mode and charge at a low current, like 200 to 300 mA. Let it run until it's fully-charged. Then discharge it at a low setting, 500 mA. Let it discharge fully and note the charged capacity, and the amount of discharged capacity. Charge the cell again and note the charged capacity and you should have a baseline of how much life the cell has in it. A number closer to the original capacity is good, but if your cell discharges rapidly, gets warm or hot, and has low capacity, then it's time to recycle it. The laptop cells were good, averaging around mAh, spot on their original capacity for all the cells. The camera battery didn't do so well. The cells were badly degraded and their capacity was down to just 550 and 660 mAh fully charged, down from their mAh new capacity. It makes sense though since this is the original battery from 14 yeas ago! I will probably use them in another project that's not a high-drain device because these size cells aren't easy to find.

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