good power tool battery-DEWALT DC540K Battery


A good cordless tool battery will help a tool perform its best, and this buying guide gives shoppers the info they need to get the most out of their cordless tools.
Because the battery is what makes it possible for cordless tools to do their work, choosing the type of battery technology that the tool uses is almost as important as the choice of tool itself.

For example, if the battery's capacity, charge time, or storage characteristics are mismatched to the work or user, the expensive tool it's attached to might not do the user much good.
Cordless power tools are used all over, and they're becoming even more plentiful. Manufacturers release more cordless models, and more powerful models, every year. On top of that, power tool battery technology is also seeing rapid changes. This means that there are more battery options out there (and we'll probably be seeing more), and that many of those batteries are expected to do heavier work than ever before.

The best thing that shoppers can do is be as informed as possible about battery designs, performance, specifications, and features to keep up with the industry. The information in this article gives cordless tool users and shoppers the head-start they need to choose the right rechargeable battery types for their cordless tools, and then get the most out of them.


Rechargeable Battery Characteristics

There are a few terms and characteristics about rechargeable batteries that shoppers should become familiar with before setting out to make a cordless power tool purchase.

Things that affect a battery's overall life and run time are usually the determining factors when power tool battery shoppers zero in on a decision (after cost of course), so most of the characteristics explained below have some influence on how long a battery will last.

cycle life-

The overall life of the battery, usually expressed as the number of charge cycles that it can withstand before completely losing its charge capacity or ability to transfer energy. For example, NiCd batteries tend to have a cycle life of 1,000 charges (cycles) or more.

All rechargeable batteries eventually wear out, although they wear out for different reasons.

Age, use, and memory effect can all contribute to the inevitable death of a power tool battery, depending on the battery type.

Users often have to choose between a long cycle life and other attractive features, like run time. For example, because they can run longer between charges than other battery types, the shorter cycle life of Li-Ion batteries isn't usually a problem for users who care more about keeping their tool in operation for longer periods.

self-discharge-

All rechargeable batteries slowly lose their charge when not in use, but some batteries lose their charge much faster than others.

For some users, batteries with fast self-discharge rates aren't a problem, especially if their cordless tool's see little or no storage. Batteries with a slower self-discharge rate become more important for tool users who plan to user their cordless tools only occasionally.

voltage-

Voltage determines how much power a battery can deliver at a given time. Simply, cordless tools with higher voltage are more powerful.

Rechargeable power tool batteries are usually a cluster of individual cells. The combined voltage of the cells determines the battery's overall voltage; however, different types of batteries (NiCD, NiMH, Li-Ion) have different individual battery cell voltage capacities.

For example, the battery for an 18v cordless drill with a lithium battery would consist of around 4 individual Li-Ion battery cells, because Li-Ion batteries can typically deliver 3.6v-4.2v per cell. Individual cell voltage for NiCd and NiMH batteries are about 1.2v and 1.4-1.6v, respectively.

Very roughly, and with some overlap, the scale for matching tool voltage to workload is like this:

Light Work: 7v-15v
Medium Work: 12v-18v
Heavy Work: 18v-36v

capacity (run time)-

This is the amount of time a battery can operate its tool between charges. A battery's capacity it usually expressed as the amount of amperage hours (Ah) that it can deliver.

"Ah" is different than the tool's overall amperage rating (the current at which the tool operates). Instead, Ah represents how much energy flow the battery can hold, not the level of current during operation.

When shopping for cordless tools and their batteries, just remember that a higher Ah means longer battery use between charges.

deep discharge-

Deep discharge means allowing a tool battery to completely drain of energy through normal operation. Deep discharge can be a problem for some batteries, and drastically reduce a battery's cycle life and capacity. For other battery types, deep discharge is not a problem.

Also , some batteries require deep discharge periodically to keep the battery healthy. This additional maintenance can be a hassle for users who do not use their cordless tools often.

memory effect-

Memory effect happens when a battery is charged over and over again without being allowed to fully drain. The idea is that somehow the battery "remembers" how much it is being recharged, and then adopts the shorter charge range as its new charge capacity.

Interestingly (and confusingly), the nickel based batteries that are susceptible to memory effect retain their capacities best when they are charged after dropping to only 70% of their capacity. However (and this is the trick), they must be allowed to deep discharge periodically so that the battery "remembers" its true capacity.

Some rechargeable batteries are sensitive to "memory effect," and some are not.