"cordless tools and battery packs"
I bought a wonderful cordless drill years ago. They were relatively new at the time and this "new" tool whispered something in my ear as I walked by! I couldn't resist and adopted it. It came with the drill, a flashlight, 2 batteries and a charger. Great deal!
Over the years, this drill served me well. The flashlight, not so much! But the drill had 2 torque settings and in low torque, can drive a #8 screw right through a 4 x 4. That's a lot of "oumph"! And then, as things happen, the tool started getting old. Perhaps I should say that the batteries started getting old. The tool still produced amazing torque but the batteries lasted for a shorter and shorter period of time. Eventually, one of the batteries spent more time on the charger than in the drill.
Okay, so things don't last for ever. I threw the bad battery pack away (that was a mistake) and went to the store to buy a replacement. Now, THAT was an enlightening experience! I remembered paying around $100 for the whole kit when new. The replacement battery...? A cool $70! It had to be a mistake, right? I called a store salesman over and discovered you are not supposed to buy replacement battery packs, you are supposed to buy a whole new drill! Duh! And what do you know, they had a whole kit, drill, charger and 1 battery for a mere $39!
I have a buddy who falls for these things all the time. He once brought back to the shop a "bubble pack" of 6 measuring tapes which were on sale. A great deal, or so it would have been if only 2 or 3 of them had 1 inch equal to 1 inch! This same buddy owns 4 of the $39 specials above. Give me a little more time and I'll make him see the error of his ways. My beef was, and still is, that the actual mechanical components of the drill are still in fine shape. More so considering that at the time this drill was made, it was manufactured here in Canada where gears were metal gears and bearings were bearings. As opposed to gears made of plastic and where "bearings" become plastic "lifetime sealed" bushings, manufactured off-shore where they think melamine is a food group! Why would I throw the unit away just because the battery pack is dead? What happened to being more "green", more socially and ecologically responsible? When the battery in your car dies, do you throw the car away and buy a new one? Who is the fool that came up with that brilliant idea?
And so the quest began. What makes a battery pack a battery pack. What makes it tick, how does it do it's job, why do they fail and how do you extend it's life, why do some last so much longer than others and why such a difference in price in some cases? Did you know there is a site called the "Battery University" on the internet? No kidding. It's at www.batteryuniversity.com of course. The site is quite legit and is actually sponsored by Cadex Electronics Inc., a manufacturer of battery analyzers and chargers. It discusses the technical merits and such for all types of batteries and can be a little "dry" to swallow unless you have a serious interest. The information is top notch.
For all intent and purposes, what concerns us poor fools with cordless tools, are Nickel Cadmium batteries in 90% of cases. Not as common are Nickel Metal Hydride batteries and top of the line are Lithium-Ion batteries. Ordinary to better to best = Ni-Cd to Ni-Mh to Li-ion. For our discussion, Ni-Cd is the topic. What is in a battery pack? A series of cells, each of which is rated at 1.2 volt. Have you noticed how the power rating of cordless tools is rarely an even number? 9.6 volt, 14.4 volt, 15.6 volt, and so on? That's because these are all multiples of 1.2. A 12 volt pack will hold ten 1.2 volt cells!
Why do some battery packs last longer than others? Two reasons, total voltage and mAh rating. The more the total voltage of the pack, the less the usable life. In fact, manufacturers have stated that battery pack life is estimated along the following lines: 1,000 to 1,300 charges for a 9.6v battery; 800 to 1,000 charges for a 12v battery; 650 to 800 charges for 14.4v battery; and 500 to 800 charges for an 18v battery. So if you are wondering why your old Makita 9.6 volt is still ticking and your new 18 volt "Super Dooper Drill" just crapped out after a year, wonder no more. The main reason is heat. Charge 1 cell and it heats up a certain amount, pack 15 of these cells together, cheek to cheek, in as small a package as you can and the heat just gets worse. You'll get enough heat generated to heat up your garage. Well, not quite of course but I have seen some cases that were pretty close with cheap battery packs and cheap chargers (More on this when we talk about chargers). Heat is the #1 killer of batteries.
The mAh rating (milliamps sustained for 1 hour) determines how long the cell will put out usable power before it drops down to "unusable". The higher the rating, the longer it puts out (and incidentally, the more it costs). Ni-Cd batteries are available in as high as 3500 mAh as far as I know. A 3500 mAh battery will give you about three and a half times the usable time over a 1000 mAh cell before needing recharging. "Usable time" for a drill for example, is from full charge up to the time when the drill turns so slow as to not be useful. The latter also happens to be the time to recharge the battery pack, or discharge/recharge every 3 months, whichever comes first.
Chargers - Because batteries are so sensitive to heat, some better tool manufacturers incorporate heat sensors in the battery packs so that the charger stops charging when the cells reach a certain temperature. Some higher end chargers even have a sensor that will first gauge the temperature of the battery pack before starting the charging operation. And because cold is also a factor, some top of the line chargers will even sense the temperature of the cells and if they are too cold, wait for them to warm up before charging. On the other hand, some chargers have none of these and that's how you get battery packs that could heat up your garage when charging! Cells are happy cells only at room temp, if you haven't figured that out already.
I've discovered that individual cells can be replaced in a battery pack to restore it to a useful level. It's not rocket science but you need to be fast to minimize the heat and you need to have the right equipment. And it's paid off quite nicely. So far, I've rebuilt a 12 volt Black and Decker, a 12 volt DeWalt, two 14.4 volt Craftsman, two 15.6 volt Craftsman and three 18 volt JobMate, with only one failure which melted the battery pack and that was due to my own carelessness. The first pack I worked on was a Craftsman 14.4 volt. Sears sells the replacement pack for $101.00, a local battery pack rebuilder wanted $72.00, an internet site that sells battery packs wanted $60.00. My cost including tax and shipping was just a tad over $35.00. I'd say that was pretty good, and I have my drill back.
Remember when I said earlier I had thrown away a battery pack? If I hadn't, I could have rebuilt that one as well. As it was, I was lucky enough to find a seller on the internet called Battery Buyer.com. They are based in Buckhorn, Ontario and they carry replacement packs for just about every power tool made at very good prices. I purchased a replacement pack from them for my first original drill at a very decent price. They can be reached at www.batterybuyer.com.
The rules for properly maintaining Ni-Cd cells applies to all Ni-Cd, whether for your tools or other gadgets. When you first get the unit, charge it to capacity following the manufacturer's instructions. This is especially important if you bought a cheaper unit with a non-regulated charger. Once charged, turn on the gadget/tool (keep your finger on the trigger for a drill for example) and let the battery discharge to an "unusable" level. For a drill this is where the thing turns too slowly to be effective. Put the battery pack back on the charger and recharge to capacity. Do this 3 times in a row but bear in mind the temperature of the battery pack. If it gets warm, let it cool down before proceeding. After this, just make sure to discharge and recharge every 3 months. I have a well cared for battery pack that has lasted over 5 years and still works very well. Do not leave your battery pack in the charger overnight unless you are absolutely sure your charger is equipped with sensors. If the battery pack gets warm or hot during charging remove it from the charger, you are only killing the cells. Do not leave your battery packs in the shed or shop over the winter unless it is heated and kept at room temp.
Back to the $39 drill kit. Let's see....drill with plastic guts, charger with no safeguards whatsoever, battery pack full of maybe 800 mAh cells also with no safeguards or heat sensor...hmmmmm $39 may even be too high a price! What is it they say?..."You get what you pay for?".
Note: The information above is a summary of what I have read. I stand to be corrected on any of the information contained, just let me know what needs correcting. I have no personal affiliation of any kind with either Battery Buyer.com or The Battery University. There is a lot more to know about batteries if you are so inclined. I tried to summarize things from a wood or shop user's point of view.