Li-ion cycles

I heard that each time a battery is connected for charging, one cycle counts. You can reach up to 500 to 1000 cycles, then the cell is practically unusable.

Sometimes, I do not exactly remember which of my batteries is charged. If I connect it to the source just for 1 second and it only shortly flashes, meaning that it started charging and has stopped immediately, does the cycle count also here for the shortest period?

Thanks

ArminVanBuuren said:

I heard that each time a battery is connected for charging, one cycle counts. You can reach up to 500 to 1000 cycles, then the cell is practically unusable.

Sometimes, I do not exactly remember which of my batteries is charged. If I connect it to the source just for 1 second and it only shortly flashes, meaning that it started charging and has stopped immediately, does the cycle count also here for the shortest period?

Thanks

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With LiIon that would only count as a small fraction of a cycle.
With NiMH it will usual count for more, because the charger will not stop immediately, but will over charge the battery for maybe 10 minutes.

How big fraction, 1/2 or 1/100?

Also, if it is not a HQ charger, does it also count as 1 in case of li-ion? One of my charger only works as plug on / out, there is only charging/charged signal, and when fully charged, it takes also about 5-10 minutes before it shows the charged signal.

ArminVanBuuren said:

How big fraction, 1/2 or 1/100?

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Probably around 1/100 cycle, but remember that time at full charge does also affect LiIon lifetime.

ArminVanBuuren said:

Also, if it is not a HQ charger, does it also count as 1 in case of li-ion? One of my charger only works as plug on / out, there is only charging/charged signal, and when fully charged, it takes also about 5-10 minutes before it shows the charged signal.

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No, LiIon chargers works another way than NiMH chargers. They cannot force extra charge into the batteries (Except old batteries), they "just" keep them at maximum voltage.

HKJ said:

remember that time at full charge does also affect LiIon lifetime

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I thought most of modern chargers automatically cut-off current supply once it's charged completely.

So even if eg in Intellicharger v4, it will a little "damage" the battery once it is left there with 3 bars indicating full charge?

Or in laptops, the battery should be removed as soon as 100 % is reached, otherwise it still receives some pulses of current?

ArminVanBuuren said:

I thought most of modern chargers automatically cut-off current supply once it's charged completely.

So even if eg in Intellicharger v4, it will a little "damage" the battery once it is left there with 3 bars indicating full charge?

Or in laptops, the battery should be removed as soon as 100 % is reached, otherwise it still receives some pulses of current?

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It has nothing with charging to do, just storing the cell at full voltage will slowly wear it down. There is a reason cells are shipped only half charged.

HKJ said:

It has nothing with charging to do, just storing the cell at full voltage will slowly wear it down. There is a reason cells are shipped only half charged.

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So the best usage range would be about 20 % ... 80 % ?

And about the charging - the current really is disconnected completely? So I don't have to worry about keeping li-ion battery in laptop when at home?

Thanks

ArminVanBuuren said:

So the best usage range would be about 20 % ... 80 % ?

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Probably. Some laptops will adjust the charge voltage if you keep them plugged in.

ArminVanBuuren said:

And about the charging - the current really is disconnected completely?

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Not completely, there is always a small leak current and the charger will usual kick in if the battery voltage drops to much.

ArminVanBuuren said:

So I don't have to worry about keeping li-ion battery in laptop when at home?

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As I wrote above, some laptops are smart enough to adjust the charge voltage for longer battery lifetime.

Battery University has a good article on how to prolong Li-ions HERE, and THIS military study on charging habits seems to corroborate it. In short, high temps, max charging, high average voltage, and deep discharges wear li-ion batteries faster/harder.

As HKJ mentioned some laptops have smart battery controls like "stop charging @ 80%," but failing that, it is pretty difficult to manage them for long life - often easier to just get a replacement battery every 2 years or so. I personally moved over to a tablet and smartphone with non-replaceable batts and manage my charging with a light timer. On average I use about 40% per day, so I just plug the devices into a light timer every night set to cycle on 70-30-70 basis, and charge between 6-8am (finished just before I start using them) - this minimizes peak charge and average voltage while leaving a reserve I'm comfortable with (30%). Only costs me a few seconds to adjust the timers if I use more or less than 40%.

Course most folks consider this practice way too anal so YMMV

HJK:

One last question.

I have seen your graph of charging 18650s in Intellicharger i4. There were pulses of current, always supplying current and then stopping for a certain period - i think for a controlling purposes, whether something else has / has not been inserted.

How come these do not count as separate cycles?

ArminVanBuuren said:

How come these do not count as separate cycles?

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The battery is not cycled (discharged/charged). What count as a charge cycle is a full discharger, followed by a full charge (Some manufactures specify a smaller range).
Pulsing the current will not affect cycle count.
What does also wear the battery down is leaving it with a full charge for extended time, especially if it is hot.

How long does the period has to be to negatively affect its life, significantly? If I charge a backup battery & let it for 2 days, does it war it out significantly? Or it has to be stored for eg 2 months in order for it to take place?

Thanks

ArminVanBuuren said:

How long does the period has to be to negatively affect its life, significantly? If I charge a backup battery & let it for 2 days, does it war it out significantly? Or it has to be stored for eg 2 months in order for it to take place?

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Generally we are talking months.
Check battery university for some numbers: http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
The article is a bit old, this means that batteries might be better than stated in that article.

ArminVanBuuren said:

How long does the period has to be to negatively affect its life, significantly? If I charge a backup battery & let it for 2 days, does it war it out significantly? Or it has to be stored for eg 2 months in order for it to take place?

Thanks

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I've had 18650 for example sit ~ a year and still be over 90% charged.

The good ones are pretty stable.

That's for emergency stand by lights....so they stay at full charge all the time for instant use.

For other lights, the cells are rotated.