Hi there, was lurking around and decided to register. I frequent all major woodworking forums and tool blogs and noticed there is a massive brand bias and misinformation about cordless power tools and batteries.
I owned, used and tested numerous tools from various manufacturers and did A LOT of research regarding batteries and their chemistries, discharge patterns, shelf life etc.
Hopefully my post will be useful to you to clarify some misconceptions in woodworking community.
1. Memory effect in NiCd batteries
First of all, I would like to talk about NiCd batteries and "memory effect" so many people talk about.
Memory Effect will only happen if the battery is charged and then partially discharged to a specific exact voltage over and over. This process causes active elements inside the cells clump together into bigger chunks thus reducing the active surface area for energy storage.
Because of irregular loads and irregular charge and discharge cycles, power tool batteries are not affected by memory effect whatsoever. IT DOES NOT EXIST in power tools batteries.
There are at least a dozen of reasons for a NiCd battery to lose capacity, and laymen ALWAYS blame it on memory effect. IT DOES NOT affect power tools.
2. NiMH Batteries
Makita pioneered NiMH cells into mainstream but never succeeded to convince other manufacturers to go along. One of the pitches was absense of "memory effect". Read #1 in regards to this. NiMH cells are great, they are light and have higher energy density (2.4 Ah NiCd is the same size as 3 Ah NiMH), relatively cheap and long lasting. One problem: self-discharge rate and maximum current. NiMH cells self-discharge nearly twice as fast as NiCd and can not provide high currents that NiCd can. NiMH cells also last approx 30% less than NiCd cells when it comes to charge-discharge cycles.
3. Lithium Ion Batteries
Not all lithium ion batteries are the same. There are hundreds of various chemistries and they all have different properties.
DeWalt uses Lithium Iron Nano Phosphate or LiFePO4 chemistry in their 14.4/18/28/36 volt NANO batteries which provides very long life (15% capacity loss after 1000 charge-discharge cycles), very high currents (70 Amperes per cell continuous, 120 A for 10 sec), great safety (slow venting in case of perforation or 100% short), resistant to overcharge, medium energy density (1.1 Ah for 18mm cells and 2.3 Ah for 26mm cells). Same cells (18mm) are used in Black and Decker VPX line.
Makita, Ridgid, Bosch, Ryobi, Panasonic, Skil use Lithium-Manganese cells which have relatively long life (40-60% capacity loss after 500 cycles) but not as good as DeWalt, moderate discharge current (15 A per cell) and moderate safety (can detonate if shorted or overcharged). Do not tolerate overcharging and perform poorly in cold weather.
Milwaukee uses Lithium-Manganese Oxide Spinel cells which allows very high density (3 Ah per 26mm cell), high discharge currents (20 A) and fair battery life (6% capacity loss after 50 cycles).
To sum it up, Dewalt are the most long lasting and the most powerful batteries with good capacity, Milwaukee have the highest capacity/weight ratio and shortest life span and Makita, Ridgid, Bosch, Ryobi, Panasonic, Skil sit right in between.
4. Torque Ratings
Never trust what the box says when buying impact drivers or drills. Manufacturers often measure peak torque by driving a screw into a predrilled hole in steel until the drill/impact stops and then use a torque wrench to unscrew it, measuring how much torque it takes to unscrew it. This is not an accurate measure and is often overblown. Makita rates their LXT drills as 560 in-lbs @ 300 rpm and Dewalt as 450 in-lbs @ 450 RPM. If you ever tried drilling wood using large auger bits or large hole saws, you will see Makita's drills poop out almost immediately while dewalt keep going until they twist your arm. This is partially bacause of battery design, but the point is Makita is NOT more powerful than Dewalt. For average everyday application you will not see any difference, but in extreme conditions Dewalt wins. Do not make your purchasing decision based on what the box says, look at the price, battery type, voltage, weight and features.
5. Brand Bias
A lot of contractors buy 1-2 tools of a specific brand, hear 1 bad story about anoher brand and make a definitive decision not to buy that brand. A lot of people bash Delta or Porter cable but praise Dewalt, even though all three are owned by Black & Decker. Milwaukee, Ridgid and Ryobi are owned by Tektronic International / One World Technologies. Craftsman doesn't even make their tools, they are made by anybody from Makita to Ridgid to a hundred other manufacturers. People bash Craftsman and then go and buy identical Makita compressor or Ridgid table saw made on the same factory.A lot of people praise Festool because it's so "good". My personal opinion is that they make tools with nice features, but they have a lot of plastic and flimsy parts and will simply fall apart on a typical construction site. Makita's 15 Amp recip saw is much better than Milwaukee's sawzall in terms of features and vibration, yet a lot of people stick to Sawzall because it's "historically" good. Dewalt's 18v jig saw is much better than any 18v jig saw out there, but people buy flimsy Makita LXT with acrylic blade change lever. Bosch makes awesome SDS rotary hammers but people stick to overpriced Hilti.
Do your research!
6. Ridgid is NOT owned By Home Depot in any way, shape or form, don't listen to HD reps. HD is merely a distributor with a contract.
Hope this is useful!