Which one cost more? battery pack or the tool(drill or impact) itself?
Doesn't matter; if the battery doesn't fit in the best tool for my money, I don't care how good the battery might be. But for the sake of argument, look up the prices. For a quality pro-grade 18V impact driver or drill, the bare tool is more than a replacement battery (slim pack or fat pack). Often more than 2X the price of a replacement battery.
Many of us wind up with tools for which we can't buy batteries anymore. Not because the technology has reached end of life (it hasn't), but because the tool companies have changed their form factor. Ni-Cd, for example, still has its place in tools due to working just dandy at low temperatures with low duty cycles. But try finding a battery for a 10+ year old 14.4V tool... in many cases, they no longer exist. If you're lucky enough to have original battery cases that are still fully functional, you can repack. But for contractor tools, batteries are sometimes destroyed by impact damage and not by charge/drain cycles. Drop it off a 2-story roof or extension ladder onto concrete or asphalt a few times in sub-freezing temperatures... buh-bye battery case.
The best design in clutch and motor is useless if there is no power to hold it, IMO.
I don't own any cordless tools without batteries. Or even sub-par batteries. I'll continue to use great cordless tools with Li-Ion and Ni-Cd batteries, and great corded and pneumatic tools with no batteries.
LiFePO4 is currently the best all around for battery. All cordless maybe excellent out of the box but over time of usage, I beleive you'll find LiFePO4 chemistry to be better than other lithium types. To understand what I am speaking of, there are a lot of information out there provided to compare the general li-ion vs lifepo4.
Irrelevant to me. If it isn't available for the best tool for my money, it's just new technology that may someday wind up in a tool I'd truly like to own.
You might choose to buy a CODA over a Chevy Volt due to a better battery and more than double on-battery range, but I personally wouldn't make that mistake. Even if the Chevy Volt had no gasoline engine and generator for extended range. The Volt is simply a much better car for the money (understatement).
A123 is the current leader in the LiFePO4 and Sony, Samsung, Sanyo haven't gotten there yet like A123.
Irrelevant to me. I don't work for A123, Sony, Samsung or Sanyo. I don't buy batteries to sit on a shelf and dream of what's inside; I buy them to power my devices. And in most cases, I get by with the batteries that come with the tool for the life of the form factor. I've had a couple of Ni-Cd repacked, but no Li-Ions have died on me yet. My now ancient (by battery usage) iPhone 3G battery still works fine, as does the one in my MacBook Pro.
I've not once had a safety issue with a Ni-Cd or Li-Ion battery in a tool. Come to think of it, I've not had a real safety issue with any battery, ever. They happen, I've just not had it happen to me yet. I've had one modern battery self-destruct on me: a very early (and hence prohibitively expensive for consumer use) development-level lithium iron phospate battery whose case cracked during thermal shock testing (standard automotive testing). Not reflective of the technology at all; a whole lot of stuff fails during early design validation. Take the data, correct the design, rinse and repeat. But I don't buy tools based on "Gee, I might have a safety issue with Li-ion or Ni-Cd batteries" because I've never had a safety issue with either in a tool and don't know anyone who has.
I've had no significant issues with Ni-Cd or Li-ion. I always have a spare battery, and they charge fast enough for me to keep one battery in the charger and cycle batteries as needed w/o a wait for charging. For home use, I typically get through many jobs w/o a trip to the charger. Even with my Ni-Cd powered tools. Of course I don't try to drive huge lag screws with a 12V or smaller tool; I use the right tool for the job. Today, an 18V Li-Ion driver will handle most anything you throw at it, if you can get it in position. I can cut multiple holes in 1.5" of hardwood plywood with a hole saw and still have charge left to drive many handfuls of screws. When I run out of charge, the spare battery is ready to go and a recharge only takes 30 minutes (15 for the slim pack). 2000 recharge cycles for a good quality Li-Ion is plenty for homeowner use and enough for almost all professional applications. For sub-0F use, I use my older Ni-Cd with no complaints.
I'll be happy to use lithium iron phosphate when it shows up in tools I like versus the competition, with no complaints.
