li ion charge cycles guestion

[chewy78]

When charging a lithium ion cell when it is 50% discharged, will I get twice as many cycles than if I charge it when it is fully discharged to 100% ? Like 1000 half charges compared to 500 full charges? Or 2000 quarter charges from a 25 % discharge?

 

[chewy78]

or is it more dependant to what voltage rather than percent of charge? like 4.1 to 4.2?

 

[chewy78]

so if i charge my li ion 18650 wolf eyes cells from my newly acquired w-e rattlesnake m90 on my pila ibc charger with only using it for 10 minutes,how many charges can i get out of those cells theoretically?

any one?

 

[SilverFox]

Hello Jason,

To answer your question we need a definition of cycle life.

I believe the industry uses a full charge and discharge to represent one cycle. If you only discharge 20%, you would have to do 5 shallow cycles to get one full cycle.

To get the best cycle life, only discharge 80% of the capacity of the cell, and use a charger that charges to 4.1 volts.

The price you pay for this is reduced capacity.

For example, if you have an 18650 with 2000 mAh capacity, charging it to 4.1 volts will reduce the capacity to around 1800 mAh, and 80% of that leaves you with around 1440 mAh.

In day to day use, this reduced capacity is usually not an issue, and you always have the option to fully charge to 4.2 volts and fully discharge on "special" occasions.

Tom

 

[Niconical]

....and use a charger that charges to 4.1 volts.

Is there a charger that is set that way by default, or is it something you would always have to do manually?

 

[Anders]

Hello Niconical.

Bantam BC-6 can charge to 4.10 V.

I am sure a lot more can.

All chargers that have a special mode for Li-Ion (3,6V).

Anders

 

[hank]

I recall reading that at least for computer batteries, Li-ion is only expected to last three years of calendar time, and that fits my experience with Powerbook batteries (replaced three in ten years on a G3 Pismo). Does this apply to single cell Li-ion, and to current cells?

 

[greenLED]

Is there a charger that is set that way by default, or is it something you would always have to do manually?

The Pila IBC Charger is what you're looking for.

 

[iamstuffed]

I don't think that's what he's looking for. He is asking if any charger allows you to charge to 4.1V automatically, without manually checking it. The Pila does not allow you to do that since it charges to 4.2V.

 

[rushnrockt]

I don't think that's what he's looking for. He is asking if any charger allows you to charge to 4.1V automatically, without manually checking it. The Pila does not allow you to do that since it charges to 4.2V.

You can always get an evaluation board from one of the battery charger manufacturers with 4.1V option

A factor that helps with battery capacity is the accuracy of the battery charger (2% vs. 1% vs. 0.5%, etc). In case when you are undercharging to 4.1V instead of 4.2V, it does not matter quite as much, but still helps. Also, 4.1V is the "safer" voltage for the 4.2V battery cells.