Cordless tool battery stability

Cordless tools batteries are simple, right? Well, Matt didn't think so when he was researching this article on cordless tool batteries. There is a lot of information there, but one thing he didn't really address was stability. His article was already pretty long, so that got left out in the interest of getting it published in the first place.

Basics of battery ratings

Cordless tool batteries are measured in Volts and Amp Hours. Volts is the amount of juice at any given moment, while Amp Hours gives reference to how long the battery can last when doing a job. That's about a simple as I can make it. Ok, one more try using a water pipe as a metaphor. Volts is the speed of the flow of the water, Amps is the diameter of the pipe that can be filled, and Amp Hours is the length of time that this flow can be maintained.

What is battery stability?

Since batteries end up having chemistry tied to them, and nobody that isn't wearing a funny white coat really wants to read about chemical reactions, I'll try to keep this more of a high level overview instead of really in-depth.

What it essentially boils down to is that stability is a measure of how many charges the battery can take before a cell goes bad. Based on the chemical makeup of the battery, this can vary quite a bit. This is also where the newer technologies really shine.

Ni-Cad (Nickel-Cadmium)

This is really one of the oldest battery technologies. The chemical makeup is Nickel and Cadmium, which ends up having the worst symptoms from voltage depression. I won't go into the details about voltage depression - you can read it at the provided link if you are interested. What I will say is that the chemical makeup of Ni-Cad means you see the least amount of time between failures in most cases.

Ni-MH (Nickel Metal Hydride)

This is a slightly newer technology, but it still has voltage depression issues. Although the symptoms aren't typically as quick to develop as Ni-Cad, they do exist and still have to be dealt with. But here's the big secret - The higher the Amp Hour rating of the battery, the less stable the chemistry of the battery. Let me repeat that in different language - Longer life per charge (higher Ah rating) means fewer charge cycles before a cell goes bad.

Li-Ion (Lithium Ion)

For power tools, this is the newest technology. This is similar to what cell phones have been using for years, but with much larger cells to give a cordless tool some actual run-time. For example, my cell phone has a 3.7V 1000 mAh battery. The smaller ones on cordless tools right now are 18V with 3000 mAh (3 Ah). That's quite a difference. But what about stability?

When talking about stability in a lithium battery, we're talking about the different chemical makeups. This is different than the concerns with Ni-Cad or Ni-MH batteries. Basically, when the manufacturers were originally attempting to make Li-Ion for power tools, there were many explosions because of chemical instability before anyone got it right.

That's not a big problem any more, but we still see people searching for V28 explosions at times. I don't know if they want video or are just doing research to make sure that they're safe, but either way it sounds like someone heard about some old problems.

Chem Is Try

The fun thing I remember about chemistry from my days at UNL is that Chem Is Try. Nothing ever comes out perfect the first time, and conditions can contribute to unseen problems. This is not only true in skydiving (as the bumper sticker to the right points out), but also in chemistry.

Milwaukee spent over 7 years on R&D for their V28 series of tools. Makita didn't want to spend that long, so they decided to use Sony Li-Ion cells which were being used in other high-demand applications (digital cameras, camcorders, etc.) already. But the point is, the battery chemistry used by these manufacturers has been tested for quite some time now to make sure that the batteries don't go boom. A few of those could cripple their reputation, and in this industry reputation is a powerful ally or an even stronger adversary.

Buying Advice - Cordless Drills for Women

At Seach Engine Strategies Chicago in 2004, we had someone stop Matt and myself as we were leaving the ballroom after lunch because she noticed the Makita logo on the sleeve of our shirts. It was Shari Thurow (pictured to the right), well known author, successful busnesswoman and speaker at those conferences. She just had to tell us how much she loved her Makita drill - not because of the power, not because of the longevity, not because of any of the reasons we normally hear. She loved it because of the weight and the fit. It seems Makita makes a drill that fits smaller hands better, and this got me thinking.

Addressing Ergonomics
Makita has long been a leader in addressing ergonomics in making tools. I knew I couldn't pick out the best tools for women, but now that the number of employees here has grown substantially and we have quite a few female employees, I've been able to have them address what's comfortable to them and what isn't. In compiling this data, I now have enough information to put together a cordless drill buying guide specifically for women based upon the unique ergonomic needs of our female employees.

Our Panel of Judges
Our panel of judges consisted of our purchasing agent, our Human Resources director and our customer support team leader. Three ladies in very different jobs and age groups, so this seemed like a nice mixture of opinions to compile for this exercise. I didn't feel it necessary to drag all of our female employees out for this, especially when the first 3 opinions were nearly identical.

Tools to Avoid
The general feeling was that 18V and higher tools, especially the Ni-Cad models, were too heavy. Most of these also didn't fit smaller hands well, specifically the trigger. The handles were a bit too deep, making fully outstretched index fingers fall short of pulling the trigger easily. Weights range here, but some are as much as 6 lbs. in an 18V, making for a heavy drill.

Battery Removal
As a general rule, buttons on either side of the battery are tougher to use. Some brands. such as DeWALT and Panasonic, have the spacing far enough apart that our panel couldn't easily remove the batteries. Others, like the Makita BDF451, have a single button to make it much easier to remove. The Porter Cable 9824 was a single button on the side, which made for fairly easy removal.

The Hitachi DS14DVF3 wasn't overly tough like some of the drills tested were, but the 2 buttons were still more difficult than the Makita and Porter Cable. We also noticed that the higher Amp Hour rated Hitachi batteries were difficult to remove. In fact, when I went back to the call center they had just finished removing the battery from a Hitachi Impact, and it took two people. That's not exactly practical.

Variable Speed
If you're wanting something easier to start a screw / hole with, then the smoothness of the variable speed trigger is important. The Hitachi had a sudden jolt of power when it started up, as did the Milwaukee models we tried. Makita and Porter Cable seemed to have the smoothest triggers. It may not be a huge issue for you, but the less you are able to put your weight behind it the more important the slow startup speed becomes.

Decent Choices
There were two that were considered by our panel to be decent choices - mostly as a backup if one of the two ideal choices below weren't available. The first was the Porter Cable 9824. The balance wasn't too bad, but the weight was a little too much towards the top of the drill. The other decent choice was the Makita 6337DWDLE, which was 4.6 lbs. with battery. The weight seemed to be a bit more towards the front, making it top-front heavy. Again, the grip was a lot better fit than most of the drills we carry. With a little better balance, the 4.6 lbs. wouldn't have been an issue at all.

Best Choices
Two drills emerged as the best choices for women looking for a cordless drill. The first is the Hitachi DS14DVF3, which is a 14.4V Ni-Cad model. This was the best overall feel, is 3/4" shorter from the chuck to the back of the drill than the next model they liked, and has a reasonable amount of power for most jobs around the house. Best of all, it weighs in at just 4 lbs. with battery. The only real concern is that the battery is only 1.4 Ah, so runtime will be less than many of the heavier models.

The second is the Makita BDF451, which is an 18V Lithium-Ion drill. It weighs 4.6 lbs. like the 14.4V model mentioned above in the "Decent" section, but the balance is much better. It is ideal for jobs where power is essential. The Hitachi has 300 in. lbs. of torque, but this model has 560 in. lbs. without a lot more weight. With 3.0 Ah batteries that last twice that of Ni-Cad and Ni-MH models, the runtime will also be a consideration point - it should be nearly 4 times that of the Hitachi on the conservative side.

This model also includes some nice features in the dual LED lights just above the trigger, easy battery removal, very smooth trigger, 3 speed transmission and a removable side handle for added stability when putting your weight behind it. The belt clip was also a nice touch, even if it probably doesn't get used all that often.

Price Considerations
Price is always a consideration when buying tools. Clearly the best value is the Hitachi, which is priced around $100 with 2 batteries, charger and a flashlight. The Makita is over 3 times as much, making it only an option when the power or runtime are essential. If you have need of more cordless tools to go along with this one, the Makita LXT400 kit has a more attractive price when considered on a cost per tool basis, and each has similar ergonomics and weight to the BDF451.

We'll Take Requests
Got a specific tool that you'd like to get our judges to review? Leave a comment and I'll have them take a look at it. If they warrant individual reviews (such as completely different tools), I'll post them that way. If you're asking about a specific drill, I'll add that to this article. Either way, we will address any requests to assist you in selecting a power tool.

Tool batteries don't get a "Memory"

In our recent Makita training, we learned something interesting. Tool batteries aren't subject to the "Memory" effect like other cordless items are.

Memory Cause
So, what is it that causes the memory effect? Well, Makita explained that it is the repetitive use of a battery at the same drain level. Basically, if you consider a cordless phone it has 3 levels. Standby is one level, on a call is a second level, and the 3rd level is ringing. Since a phone spends most of its life in standby, or (if you continually charge it) always on a call, the end result is that the battery gets the same load level repeatedly. A camcorder is a more extreme example, since playing and recording are almost exactly the same level of draw.

Why doesn't this affect tools?
Since tools work on different types of material, run into knots in wood, use different size bits and are variable speed, there is a wide variety of draw levels for the batteries to get accustomed to. The result is that the memory effect is minimized or even eliminated. Chances are that a tool battery will have a cell go bad and quit taking a charge long before it can develop a memory.

Why newer technologies?
In cell phones, the newer battery technologies (Ni-MH and Li-Ion in place of Ni-Cad) were primarily to deter a memory. Each technology was less prone to memory than the technology before it. So why do tools need the upgraded batteries? Runtime, power, consistency and the environment. The Li-Ion tools have a longer runtime, in many cases twice that of previous technologies. They also offer more power that is much more consistent through a charge, making the first use similar in power to the last use of a charge. Ni-Cad is also extremely harmful to the environment, although the others aren't really "good" for it. They are just considerably less harmful than Ni-Cad.

Lower voltage batteries - a Makita secret

One of the most unusual little known facts about Makita cordless tools is that any of their pod style batteries can power a tool made to run on a higher voltage, just with a shorter runtime. This has some very interesting applications, especially buying new tools.

Keep using your old batteries
If you buy a newer Makita tool, you don't need to worry about your old batteries becoming obsolete. For example, if you had a 12V drill before and decide to buy a 14.4V impact, the 12V batteries will still work in the new tool. If you had a 14.4V drill that broke, you could buy an 18V no problem without losing the use of your old batteries.

Save money when buying additional batteries
If you want to save a few bucks on your next set of batteries, you can always buy a lower voltage. That's a unique ability. If I decide that 18V batteries cost too much, I can buy 12V or 14.4V replacements. I don't know of any other brand that is set up this way. Very useful for buying batteries for a flashlight, probably not so cool for buying batteries for my miter saw.

Borrow a battery
My neighbor has 12V Makita tools. If I'm in the middle of a job and run out of juice, I can borrow one of his for any of my 18V tools. That could be handy at times. Of course, having 4 batteries of my own means there are few instances where I'll have to borrow a battery, but it's still nice to have the option.

Reminds me of blood types
This reminds me of blood types. Having a 12V is a universal donor (Type O). Owning an 18V tool is a universal recipient (Type AB). Of course, with Lithium Ion coming out now this isn't going to be a universal technology much longer. Also, the MakStar tools don't fit in the same interchangeable line, either. It's still something cool that you can amaze your friends with. Tell them to try that with their "other brand" tools.