Consideration on 80% rule

[nitros]

As far as I know most of our, day by day, devices now a day use lipo as battery, iPhone, iPad, laptop, sat nav, our tx, etc. Now I was wondering why all those device the have alarms/ low voltage, set at 20% of the battery capacity. I might be that the 80% rule is overrated?


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[electricsceadu]

my new laptop battery instructions said to run it down to 3%
and store at 80%

[Gixxer]

I think it might have something to do with the fact that 99.9999999% of the things we use on a daily basis with LiPo, don't have the current draw that a heli has, and a drop in performance won't be noticed.

I think that no matter what device with what battery type you use, if you look after the battery properly, it will last a lot longer than if you just charge it when you feel like it.

[paulsouthport]

The discharge circuits on most smart devices have a "safe discharge" rule factored in. 20% on iPhone means 20% of safe capacity left, not 20% of total capacity.
What they use as a safe limit is something else, and I don't think they treat the lipo with quite the same respect as we do, but still, better than nothing...

[cjcj1949]

The laptop batteries are liion rather than lipo. It seems difficult to keep a laptop battery charged to less than the max, but you only need that occasionaly. Lipo chemistry has not been properly published. It remains a black art.

[GravityKills]

BTW I run my (expensive) LiPos down to 3.3 or 3.5 V / cell open-circuit voltage regularly and haven't noticed any degradation.
Don't abuse them with high current at the end of the discharge.

[Zeeflyboy]

As above, you are assuming that when, for example, your iPhone hits 0% that it means the battery is dead.

It doesn't... You can see this because if your phone shuts itself down, and you try and turn it on, it will power up the screen and show yu a battery symbol telling you to charge it. It couldn't do this if the battery was totally flat.

All these electronics have battery controllers which monitor and look after the battery. They have a shut off point (what actual percentage of battery remaining that is, who knows... Could be 15% could be 5%, and I imagine it varies depending on battery chemistry and manufacturer) which is what is reported to you as 0%.

The 80% rule may be a touch conservative for us, but it's a good way to ensure your lipos aren't damaged from over discharge. If you accidentally go to 90% occasionally then no biggy, you have the margin because you were aiming for 80%.

[alioth]

The laptop batteries are liion rather than lipo. It seems difficult to keep a laptop battery charged to less than the max, but you only need that occasionaly. Lipo chemistry has not been properly published. It remains a black art.

LiPo is Li-Ion, the full name for LiPo is "lithium ion polymer". They have the same operating principles, just different materials to construct them (which may make differences in looking after them even though the basic chemistry is just another lithium ion battery). Incidentally, many laptops now use LiPo such as the Macbooks (which have built-in batteries). An advantage of LiPo is that you can make them in a shape that fills a case more efficiently (instead of cylindrical cells, you can have something flat that more efficiently fills the space, so get more capacity).

[cjcj1949]

Yes I agree Lipo is Lithium Ion. All batteries work on ions. The term Li-Ion did come before LiPo. I was trying to refer to the differences between the two types. There seems to be more of a problem with keeping lipos fully charged rather than than the older non polymer battery. The non polymer Li-Ion in laptops have protection circuitry built in and operate at much lower C rates of charge and discharge. Each Lipo that we use will be a different brew of compromises, which unfortunately we are not told about. We do know though that they are getting better, lets hope they get cheaper as well.