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Rechargeable batteries life and cycles - best practices

Follow Discussion Posted by Dexter on Jul 07, 2011

We’ve been dealing with mobile products since many years, which all have one thing in common - batteries. Rechargeable battery types are quite a few, but the winner with the most wide-spread usage is the Li-ion battery which can be found in notebooks, cell phones, multimedia players, tablets etc. I’ve been researching the subject for some time now, but cant make any general conclusion what’s best for extending the battery life of our gadgets. What I’ve been doing so far with my notebooks is:

- Using it unplugged every day for at least half an hour
- If I’m not going to use it for a couple of days, taking battery out (60-70% charged)
- Full discharge once per 2-3 months

However, there is one thing I’ve never quite understood - the battery charge cycle. Most of the manufacturers are saying batteries should take approximately 300 charge cycles before causing any problems (although, high-end models take that up to 1000 charge cycles). So I’ve been wondering, what is a charge cycle? Is it every time I charge the battery up to 100%? I tried to figure it out and here’s what I figured so far:

Day 1, initial charge 100%, after usage 50% left. Charging that to 100% makes 50% of a charge cycle. Day 2, initial charge 100%, after usage 50% left. Now, after charging the battery back up to 100%, makes one full charge cycle (50%+50%). If that is correct and I keep using it unplugged from the mains for half an hour per day (~30%) the battery should stay on near-to-perfect shape for about 3 years (correct me If I'm wrong)?

So, what do you think is the best way for optimal battery use in order to preserve it’s capacity?

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Level 9 1 Immortal on Jul 07, 2011

A charge cycle is the single iteration of depleting and charging the battery to 100% of its charge. If for example you consume 50% of your notebook power and charge it to 100% the next day when you do the same you just finished one charge cycle. The capacity loss of the lithium ion batteries is also connected with the temperature on which you`re using them. For example at 40% state of charge at 40C(hypothetical) for a year the battery is going to loose 15% of its overall capacity and at 25C only 5%. The notebook batteries(maybe other types too) should be fully discharged every 30 cycles it is called calibration(not doing this causes the battery to suddenly go from 25% to 5% charge for example).

To summarize:
- Stop discharging frequently(it is better to charge several times after partial discharge, then recharging after a complete discharge)
- Calibrate the battery every 30 cycles
- Keep the battery cool
- Check manufacturing date(the Li-Ion batteries wear out in time)

I`ve read at several places that when you buy sth with a new Li-Ion battery you should discharge it fully...completely wrong the battery memory problem doesn`t apply for anything after NiMH batteries. Fully discharging your lithium ion battery frequently can significantly shorten its life and it is possible to make it completely unusable if power levels go too low. I think that most Li-Ion batteries have safety circuit to ensure that the power doesn`t go too low but it happened to me several times anyway...