Lithium batteries - first charge is max charge?

A friend of mine is buying a computer for the first time, and this got me thinking of something that, well, I have believed for ages, I think, but can’t recall where it started.

I remember hearing somewhere that for all rechargeable batteries, especially laptop lithium batteries, you have to leave them charging for, like, 24 hours before you first start them, them, because the amount of charge you give them that first time will set their maximum forever after - so if you turn on an object with a rechargeable battery immediately after plugging it in, then it will be wedded forever to that power cord and the battery will be useless.

Is there any basis of truth to this wild superstition? Was it once true, but no longer is?

I believe that was true with older NiCad batteries. Modern lithium batteries have a built in chip that cuts off charging when the battery is full.

So once the charging light goes green it stops charging. It doesn’t matter how long you let it plugged in after that point.

“memory effect” was only really a concern with an old type of NiCd cell. Lithium-ion cells have no memory effect, and sophisticated charging controllers which will do what is best for the cell(s) regardless of what you do.

If there is any truth in this, it’s going to be so that the firmware that controls and monitors battery charging and discharging (including reporting how much charge is left) can set its upper limit based on any small idiosyncrasies of the actual installed battery.


How to Prime Batteries - from Battery University.

The ‘first time charge setting maximum charge forever’ sounds like all the other bullshit non common sense techno myths people like to spout. Crap like ‘a light bulb uses more energy to turn on so dont turn them off’. The whole ni-cads (and somehow other batteries) need to be completely drained myth has pointlessly reduced the life of most batteries because of user error.

I heard that too - except I think the part about maximum capacity.

I noticed that coincidentally, that was when lithium batteries came empty. Now they come partially charged. Could it be that, if this were true, empty batteries ship better / cost less / store better, but too many customers weren’t initializing them properly, so manufacturers now prefer to charge them for the customers instead of handling complaints about short battery life?

lithium batteries don’t have the memory issue that occurred with NiCads.

fully charging the battery is still good. the battery may be in a low capacity due to long storage and you don’t want to depend on run time that isn’t there. you want to charge and discharge the battery a bunch while under warranty to see it works as it should.

Li-ion is usually limited on the top and bottom end by a chip, as if you charge much beyond what we see as 100% on the gauge you shorten the life of the battery, and if you drop much below 0% on the gauge you drastically reduce the life of the battery, but the battery is chemically capable of more then we get.

The charging cycle is not to condition the battery in any way but to get the controller chip data points to better regulate the battery. The recommendation to cycle Li-ion batteries actually hurts the battery, as with Li-ion as you get to low charge levels the electrodes break down much faster, but the new data points helps the management of the battery which is taken as a overall positive if done infrequently.

on lenovos their battery software does show you the capacity, and the rated capacity, you get to watch the actual capacity drop over time vs the rated… you don’t set the original capacity though, its just how it works, cycles age, heat ages, shelf life ages, everything kills these things.