Li-ion only charge to 80% and it will live longer?

[TinderBox (UK)]

I have noticed that a lot of new notebook offer the choice to charge the battery to 80% instead of 100% and they say that you will get more cycles out the the battery at the cost of reduced run-time.

I wonder why they picked 80% , why not 90% , and how many extra cycles you get by only charging to 80% is it worth it?

Also what voltage is 80%

Thanks.

 

[Black Rose]

I wonder why they picked 80% , why not 90% , and how many extra cycles you get by only charging to 80% is it worth it?

I went looking for the thread on this but can't find it now.

Charging a cell to 4.2v will give it a life of about 300 cycles.
Charging a cell to 4.1v will give it a life of about 1000 cycles.

It's only .1 of a volt, but the effect on the cell is huge.

Also what voltage is 80%

This chart is simply a guide to use voltages to determine how full a Li-Ion cell is.

4.2V = 100%
4.1V = about 90%
4.0V = about 80%
3.9V = about 60%
3.8V = about 40%
3.7V = about 20%
3.6V = empty
<3.5V = over-discharged


The problem when it comes to laptop battery packs is that the heat generated by the laptop itself also has an effect on the battery pack.

Here's a link to Battery University with some more info on Li-Ion battery life: http://www.batteryuniversity.com/parttwo-34.htm

 

[Anders]

"The cell phone industry did a study looking at the effects of ending charge voltage on cycle life.

Under laboratory conditions, and with an 80% depth of discharge, terminating the charge

at 4.1 volts, you get over 2000 cycles.
at 4.2 volts, you get roughly 500 cycles.
at 4.3 volts, you get under 100 cycles.
at 4.4 volts, you get less than 5 cycles.

The RC people have seen similar results, and one test that is ongoing is at roughly 800 cycles with a charge termination of 4.15 volts. This seems to be the sweet spot for performance and cycle life.

In normal use, you can extend the life of your battery by limiting the maximum charge to below 4.2 volts, and limiting the depth of discharge.

Tom "


http://www.candlepowerforums.com/vb/showpost.php?p=1902424&postcount=4

Here is also a good article of how to extend the life of Li-Ion batteries:
http://powerelectronics.com/portabl...r_care_extends-li-ion-battery-0425/index.html
Anders

 

[TinderBox (UK)]

The above post see a little too good to be true , as heat and age of the battery also play a role in the number of cycles.

I think if i can get 750-1000 cycles charging to 80% , it`s worth the 20% loss in runtime for my needs.

Thanks for the help.

 

[DM51]

For maximum cell life, charging to 4.1V is probably the best. If you only charge to 4.0V, you will be operating in the cell's mid-to-low range the whole time. Bear in mind that 2,000 cycles means the cell will be ~6 years old if you fully cycle it every single day - and deterioration because of age is more likely by then.

You'll have saved a huge amount of $$ and had tremendous value from it at 4.1V max, and you'll have had best value from the cell too.

 

[SunFire900]

May I ask: What would be the easiest and least time consuming way to charge 8x 18650 cells to 4.10/4.15 volts?

Charging these cells to anything less than the "auto. charger cut-off" voltage is an tedious and time consuming ordeal. You have to constantly check the cell voltage and it can not be done while the cell is taking a charge. So, you have to remove each cell from the charger several times, check the voltage, put it back in the charger and repeat this process over and over again.

Do we all need to buy $300+ hobby chargers to charge our cells?

We need easier and cheaper solutions to this quandary.

 

[Black Rose]

A low cost hobby charger that is getting good reviews is the Turnigy Accucel-6 - $34.99 plus shipping.

It needs an external power supply, which can be had for about $18.00.

There are other <$300 options as well such as the Hyperion 1210i.

 

[SunFire900]

A low cost hobby charger that is getting good reviews is the Turnigy Accucel-6 - $34.99 plus shipping.

It needs an external power supply, which can be had for about $18.00.

There are other <$300 options as well such as the Hyperion 1210i.

Thanks for clearing that up for me, Black Rose. What I really had in mind was an li-ion charger that is as portable and as easy to use as the Pila IBC and others and incorporates the user assigned voltage cut-off ability.

Most of us do most of our charging at home (I think) and not on the road, so the Turnigy entry level charger would do just fine. I might just give one a try.

 

[clintb]

Thanks for clearing that up for me, Black Rose. What I really had in mind was an li-ion charger that is as portable and as easy to use as the Pila IBC and others and incorporates the user assigned voltage cut-off ability.

Most of us do most of our charging at home (I think) and not on the road, so the Turnigy entry level charger would do just fine. I might just give one a try.

Good thing about the Turnigy, is the presence of a DC input jack, like the type on a laptop. Check out this power supply. It's only 5A @ 12V, but that should be good enough for charging when not at home, if you wanted to take it with you.

Here's the Turnigy Accucell-6 at Hobby City.

 

[bcwang]

Now here is another interesting thought that I wonder if anyone has an answer to. Let's say with each charge, you use up exactly the same amount of power. So what would be better for the battery?

-Charging to 100% and draining to 25% before recharging
-Or: Charging to 80% and draining to 5% before recharging

Li-ion don't like to be charged too high or discharged too low, so which is the worse of the evils?

 

[45/70]

Now here is another interesting thought that I wonder if anyone has an answer to. Let's say with each charge, you use up exactly the same amount of power. So what would be better for the battery?

-Charging to 100% and draining to 25% before recharging
-Or: Charging to 80% and draining to 5% before recharging

Li-ion don't like to be charged too high or discharged too low, so which is the worse of the evils?

Interesting question, bc. I'd take a wild guess and say those two options would work out about the same, but I really have no idea. I hope someone has a credible answer to your question.

I have always charged to 4.20 Volts myself, figuring that my Li-Ion cells will degrade from age before I run them through 300 or whatever cycles anyway and, if I need the mAh, it's there. I rarely discharge them to less than 3.75-3.80 Volts. At the same time, I don't charge them up to 4.20 Volts and then let them sit around, rather I use them right away. As I've said elsewhere, when my Li-Ion cells are not in use, they are in the fridge at 35-40F @ ~40% charge. When they are installed in light and not in use, they usually are somewhere between 3.80 and 4.00 Volts.

Dave

 

[Anders]

Hello bcwang.

I'll would say that charging to 100% and discharge to 25% would be much better than the other way around, charging to 80% and draining to 5%.

That would be better for the battery.



Anders