Does recharging your batteries too early ruin them

Question

Does recharging your batteries too early ruin them

Answer 1

The last guy almost has it, it is true Ni-Cads did have a sort of memory effect, and it is true that Li-Ion batteries do not, but neither do most rechargeable batteries.  For most batteries a complete discharge actually ruins them (Li-Ion, Lead Acid, Gel Cell).

Answer 2

It depends on the battery.

The older NiCAD batteries (usually the older AA cells, occasionally the cells used in R/C cars, but pretty much on the outs these days) have a thing called the "memory" effect. Basically, if they don't get fully discharged, they don't remember their full charge capacity. Some sophisticated chargers may be able to fix this a bit, but most people don't have such chargers (these are used in R/C racing circles, and run around $100 or more).

NiMH cells have some similar issues, but they're not as bad. You'll find NiMH cells are usually the drop-in cells of choice these days, for AA, AAA, C, D, etc. applications, and still occasionally found in other appliances. It's still best to let these drain fully, and some of the better chargers will cycle them, draining them empty before recharging them. One disadvantage of NiMH over the others is that they self-discharge pretty quickly... so you can't charge up a set of cells a week before your vacation and expect to have fully charged cells on the trip; charge them as close to the time you'll use them, in general. However, there are some new NiMH technologies on the market which last much longer against self-discharge... the makers of these typically sell them charged -- kind of a gimmik, but it would be impossible with the older formulas.

Most small devices, such as cellphones, laptops, iPods, etc. use Lithium-ion cells (Lithium-poly is a kind of Lithium-ion cell, with a dry polymer used as the electrolyte). Lithium cells have a much more complex charging cycle, but don't suffer from any sort of memory effect in normal use -- you can drop in them in the charger anytime without affecting the cell's capacity. If you fully discharge a Li-ion cell (if the individual 3.6V cell drops much below 1V), you can kill it for good, but most devices using Li-ion cells don't allow this.

There are other technologies for "secondary" batteries, like the lead-acid battery in your car, but these are not much of an issue, since most people never recharge these on their own.

All cells today have a variety of aging effects. Every time you charge-cycle a battery, it ages a bit, and it will eventually die, usually after something like 500-1000 charge/discharge cycles (by "die", that's usually regarded as the point where the maximum charge is only 80 percent of the original... it's not dead-dead, but it's weak, and will drop off pretty quickly in use). Li-ion cells also age in realtime... depending on the mix, they can die in 2-3 years regardless of the level of use. Li-polys have the same problem, but tend to last a bit longer.  

Answer 3

Ni cad batteries suffer from what is called "Memory Effect" which means that if you recharge them before they are fully discharged then they will deteriorate. Lithium Ion batteries do not suffer from this effect so can be safely recharged irrespective of what state of charge is in them .