Battery mythbusting

[macboy]

...
Apple in their manual for the Ipad devices state that the lifetime is depending on the number of chargecycles, that it doesn't matter if it is a complete charge from for example 30% to 100% or from 60% to only 70%, doesn;t matter both count for the same decrease in lifespan.

You have misinterpretted their information. According to Apple, one "charge cycle" means using 100% of the charge. So if you use 20% then re-charge, and repeat this, you can do so five times before it counts as one cycle. In other words, using 20% of the battery capacity, then charging it, counts as 20% of a 'charge cycle'.

From http://www.apple.com/batteries/ :
"A charge cycle means using all of the battery’s power, but that doesn’t necessarily mean a single charge. For instance, you could listen to your iPod for a few hours one day, using half its power, and then recharge it fully. If you did the same thing the next day, it would count as one charge cycle, not two, ..."

I have seen other research that indicates that more shallow cycles degrade the battery less than the fewer deep cycles (with equivalent watt-hours used in each case).

[Kjelt]

Apple in their manual for the Ipad devices state that the lifetime is depending on the number of chargecycles, that it doesn't matter if it is a complete charge from for example 30% to 100% or from 60% to only 70%, doesn;t matter both count for the same decrease in lifespan.

Then they must have changed the information, I can almost with full certainty remember when I bought my first iPad in 2010 I was astounded to read online that each time you connect it to the charger it would count as a cycle.
Ok good for them that they now have clear and precise info with examples what counts as one cycle. 

[abbotsmike]

everyone has something to say on this.  I think only one person has mentioned what their goal was; maximum battery life or maximum power storage.  your choice there will determine how you treat the battery.  most folks assume that maximum battery life is the goal, and it's certainly my goal, but I've never once stopped my laptop charging at 80% intentionally.

my point is that it's a pain in the ass to take care of batteries properly.  someone needs to rectify this.  i'd pay more to know that my charger took better care of my batteries.

My Samsung laptop has an option to only charge the battery to 80%, so I use it. No real hardship as I can squeeze out 6 hours on one 80% charge if I keep it in power saving mode! Every so often I will fully charge it if I know I need the extra runtime without a charge available.

[ejeffrey]

The memory effect of NiCd and NiMH batteries is mostly a myth.  While NiCd does have a memory effect, it is rarely observed in practice.  The reason for the 'discharge before charging' rule is simple:

*all* rechargeable batteries hate being overcharged.  Early NiCd and NiMH chargers were simple timers with a fast charge cycle followed by a trickle charge.  If you discharge a battery half way and then put it in a dumb charger, it will be overcharged and damaged.  Modern NiMH chargers that charge faster can't do this.  Instead they detect voltage or temperature changes to detect when charge is complete.  With these chargers, there is no need to do a full discharge.