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I bought a combo drill & driver kit recently and I really love it, but it came with "XC" batteries that are 4Ah. I went to buy one of the slim packs because sometimes the large batteries are just too heavy for what I am doing - but even the slim packs are $70!

The kit I bought came with a drill and driver and 2 XC batteries. Each XC battery costs $130 retail, but I only paid $390 for the kit. At retail value that means the drill and driver and charger were only 130. (Drill and driver and charger are same price as one battery?)

The math just doesn't work out. So, why are the batteries so expensive!?

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Because they can. –  Steven Jan 17 '13 at 13:06
    
It sounds like this question would fit better on Economics.SE or Marketing.SE, if they existed. Questions about the price of items; especially why things are priced the way they are, is off topic here. –  Tester101 Jan 17 '13 at 14:57
    
I'm late to the party here. The cordless drills are typically junk, and the batteries are overpriced, burn out easily, and die in under 2 years if they don't burn out first. You're best off with a corded drill with a metal keyed chuck. I was silly enough to buy a corded, hand-chuck drill from Home Depot. The only way to get the bit to hold in the chuck, I needed to use a pair of vice grips or channel-lock/jaw-tongue pliers to close it. Even then, the bit slipped and was dangerous. Avoid battery-powered and hand-chucks like the plague they are. –  Dogbert May 23 '13 at 22:59
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closed as off topic by Niall C., Steven, ChrisF Jan 18 '13 at 23:43

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2 Answers

Most battery operated power tools run on Nickel Cadmium type batteries. This is ideal as they have a very high energy density and can provide a steady voltage for an extended period of time unlike cheaper zinc and alkaline batteries.

Lead acid batteries are cheaper to manufacture, but are significantly heavier thus are not a good application for a portable power tool. Cadmium is an expensive material, and that certainly plays a huge factor into why the batteries cost what they do. Cadmium is also in many ways more toxic than even Lead.

Nickel Metal Hydride however is in many ways however superior and may soon be a universal replacement in power tools. They are cheaper, far less toxic, and have a higher capacity. The only drawbacks are they lose power quicker than NiCad when sitting idle, have a lower maximum discharge rate, and NiCad can sustain prolonged periods of heavy discharge without damage.

The bottom line is that portable power tools need high discharge amounts, high capacity and need to be rechargeable and sealed. These are not possible with cheap batteries.

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I think you covered all the common battery chemistry except lithium-ion. It can have up to 730 watt hours per liter. It's also stable when charges and does not self drain quickly. –  Malfist Jan 17 '13 at 14:00
    
@Malfist Correct me if I am wrong but doesn't lithium ion do poorly on rapid discharge? I thought that they get extremely hot when drawing heavy amperage (See the Boeing 787 Dreamliner problems). Perhaps that is why you don't see these types of batteries in use for power tools. –  maple_shaft Jan 17 '13 at 14:07
    
From what I understand of the dreamliner issues is they either didn't cool the batteries enough, or over charged them. Typically it takes a very large drain over a significant amount of time to cause them to overheat enough to be dangerous, and it's not likely to happen from a drill. (They can also overheat from too rapid charging, but they can charge faster than any other type of battery chemistry) The limiting factor with li-ion is it's cost. Their batteries are even more expensive. –  Malfist Jan 17 '13 at 14:18
    
@maple_shaft: I've used several tools powered by Li-Ion batteries - they work just excellent. The key is how the tool is designed. It should monitor the battery temperature and limit the load if the battery gets too hot, in this case the tool produces less output power but the battery remains okay. This regulation only kicks in during really heavy usage. –  sharptooth Jan 18 '13 at 8:48
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That's usual practice among manufacturers. They make kits cheaper so that you get on hook easier, then they charge a fortune for "accessories". Also battery production is a high-tech process involving lots of toxic chemicals, so it's not really cheap to make a powerful reliable battery.

Here's how you benefit from it. Many manufacturers offer various tools for the same voltage batteries and the same batteries can be used with each tool. There's a chance the brand of your choice has some other useful tool that comes with the same voltage batteries that are slim, not "extra large" and the tool with the batteries will cost the same as your batteries if choice alone. This way you get a variety of interchangeable batteries, an extra tool and a spare charger.

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That is why I have four DeWalt drills! lol Cheaper to buy a sale/deal with a tool and two batteries and charger than to buy the batteries separately. –  shirlock homes Jan 17 '13 at 12:34
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