Fast vs slow charging li-ion batteries (0.8C vs 0.4C)

retched

Joined Dec 5, 2009
5,207
.....ok, friend.. When you buy eggs, there is a label that says the size of the eggs and the number of eggs in the carton.

If you wait 7 years to use them, thats on you. Drop the carton, thats on you. But open the box and WHAT? ONLY 11 eggs? Thats on them.

The manufactures can give WHATEVER they want as numbers. If you can prove you followed their data and didn't abuse the battery, and got less than printed charge cycles...

....You get a NEW battery. They will say the crap that you are saying "well we strive for blah blah blah. It must have slipped by our quality assurance guys." Go out of the parameters and it is on you.

I dont care about what you measured where and when. Manufactures MANUFACTURE TO A DETERMINED LEVEL FOR DETERMINED USE. That is where the X number of charge recharge cycles come from.
 

Norfindel

Joined Mar 6, 2008
326
From what I understand. Heat or full discharges do shorten the total lifespan of a lithium battery. Best to keep topping it up with charge before it gets lower than 60% or so.
This site disagrees: http://www.batteryuniversity.com/parttwo-34.htm
You're right about heat, and not getting the battery deeply discharged, but 100% charge for extended periods also wear the battery. The best thing to do, would be keep the battery at 40% charge, and fully charge them when you're actually going to unplug the device, and take it away.

Cellphones are ok, because you charge them and then disconnect, and the battery is always on use, it's not kept connected at 100% charge all the time.

Notebooks, on the other hand, are likely to be connected a lot of time at 100% charge, and at high temperatures.
 
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sceadwian

Joined Jun 1, 2009
499
retched..

Charge and discharge rates and number of cycles aren't listed on ANY battery I have ever found. You'd be more than a little hard pressed to provide a data sheet from a battery maker that listed charge and discharge rate's that were guaranteed to deliver a certain number of charge and discharge cycles. If you can post one that didn't have disclaimers as to the charge/discharge cycle value and charge/discharge rates I'll send you a certified check for 10 dollars.

Very few if no makers of a device fully characterize their batteries properly, and no batter maker will provide a battery without a disclaimer as to void certified ability to perform a given task. The only exclusion you will find to this general rule is with medical batteries which cost an arm and a leg to meet STRICT standards.

Look at the number of devices in the last 5 years that use lithium cells that have had catastrophic failure and massive recalls because of insufficient design insight.
 

sceadwian

Joined Jun 1, 2009
499
Notebooks, on the other hand, are likely to be connected a lot of time at 100% charge, and at high temperatures.
This is completely opposite of what should occur.

If the notebook is connected it will be using power from the wall not from the battery, so the battery should be stone cold. If the battery is heating when connected to the power supply then there is a failure of the design of the battery because Lithium cells are incredibly efficient ANY heating is from over charging or discharging. If the battery is hot from increased ambient it is a failure of the laptop designer to implement proper thermal control (unfortunately common)

Modern designs are using less power and because of past failures in this department are paying a little more attention to thermal concerns, but it's hardly an overnight change.
 

retched

Joined Dec 5, 2009
5,207
Marketing and BS aside, ANSI has requirements for battery measurement - size, voltage, capacity, and charge/discharge cycles - these are defined. I dont care about what is printed on what battery or advertisement. Everything made today is crap.

You are NOT going to find them on a standard consumer battery. The manufactures marketing guys are not stupid. They know most people have not read the ANSI definitions. A look on energizers web site will simply say:

In normal use, NiMH batteries can be recharged hundreds of times. Many factors effect cycle life. Some of these factors include depth of discharge, charge and discharge current, method of charge control, storage and operating conditions and shelf life. Typically batteries with a higher mAh capacity will have a lower cycle life than lower mAh capacity batteries.
They started putting an expiration date on batteries to make folks think they will EXPLODE if they are used after that date. It was only done to sell more batteries.
 

Thread Starter

Grayham

Joined May 18, 2010
79
Thanks for all your advice and tips.
But let me ask the original question in another way (with image diagram).
Which charging method is going to give me more 'one-off' runtime on my battery charge.
Figure 1 or Figure 2?


Think of R3 and R2 are actually batteries (not resistors).
 

retched

Joined Dec 5, 2009
5,207
Figure 2 will charge the battery slower, thus cooler. It will lead to a longer battery life, if your charge TIME doesn't kill the battery.
 

SgtWookie

Joined Jul 17, 2007
22,230
You don't charge Li-Ion batteries using a resistor.

You use a proper charging circuit. The best thing for a novice to do is to use a commercially available charger that is specifically made to charge their battery type.

There are lots of different types of batteries, and the charging recommendations for even the same basic chemistry batteries can vary considerably from manufacturer to manufacturer.t

As a very generalized statement, the slower you charge or discharge a battery, the less internal heat will be created; and the cooler the battery core is, the less chemical activity there will be, so the battery will "eat itself" more slowly.
 

Audioguru

Joined Dec 20, 2007
11,248
Both extremely simple charging circuits do not limit the voltage to 4.2V and turn off when the battery charging current drops, so the battery will become over-charged and will probably catch on fire.

The currents are calculated when the extremely simple "charging circuits" are feeding a dead short, not a battery.
 

sceadwian

Joined Jun 1, 2009
499
I doubt they'll catch on fire AG, it takes a LOT of over current to cause a lithium to combust, and even at full charge it takes a massive discharge to cause the thermal runaway which causes a fire. The given resistor even under dead short conditions won't do more than 1amp, it will fully charge then kill a lithium cell, no fire. Unless it's smaller than about 250mah, Anything less than about 500mah past a full charge will get quiet warm, puncture could cause a fire or if the fully charged cell is otherwise compromised, such as a steep discharge.
 

Audioguru

Joined Dec 20, 2007
11,248
Most Lithium battery cells can discharge many amps when shorted which heats them so they catch on fire.
If the voltage is too high or too low then Lithium-ions form into metallic Lithium that is a dead short to cause the very high current and very high temperature.
 

Norfindel

Joined Mar 6, 2008
326
Li-ion batteries are complex, and so are it's chargers, that often measure the battery internal temperature, current or voltage rate of change, and charge the battery in several different steps.

According to the link you provided, the battery pack itself has an USB input, and the charger an USB output.

Charging a battery slower cannot hurt under any circumstances, so if you aren't in a hurry, charge it with USB.
 

Thread Starter

Grayham

Joined May 18, 2010
79
Li-ion batteries are complex, and so are it's chargers, that often measure the battery internal temperature, current or voltage rate of change, and charge the battery in several different steps.

According to the link you provided, the battery pack itself has an USB input, and the charger an USB output.

Charging a battery slower cannot hurt under any circumstances, so if you aren't in a hurry, charge it with USB.
Yeah, I might actually benchmark it myself. I know there is a significant charging time difference between the two. But am very interested in the runtime each provide.
 

sceadwian

Joined Jun 1, 2009
499
Grayham, that is not a battery. That is an input regulator, an internal battery and a output regulator all built into a single unit with all the circuitry provided.
 

sceadwian

Joined Jun 1, 2009
499
Norfindal, Lithium Ion/polymer batteries aren't really that complicated, I used to think that till I found basic documentation on their limits. They're different than other batteries, the same basic thing is occurring though. I've charged and dischargeds a half dozen different cell succesfully using nothing more than a current regulator and a multimeter.
 

Thread Starter

Grayham

Joined May 18, 2010
79
Grayham, that is not a battery. That is an input regulator, an internal battery and a output regulator all built into a single unit with all the circuitry provided.
Yeah I know that.
But affecting the input current is still going to affect its internal charging method.
 

sceadwian

Joined Jun 1, 2009
499
If this unit you have is designed to work off USB it probably doesn't have an internal regulator on it's input, just a buffering capacitor, feeding it any other voltage besides 5.0 volts exactly to adjust it's current will cause unpredictable results, it could easily cause either a failure of the circuitry, under performance, or depending on the regulation circuitry it could also cause the proper charge control to the internal battery to be lost and cause the battery to catch on fire.
 
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